Tungsten carbides represent the primary sector of the tungsten products industry. This article analyzes the current practices of major global Tungsten carbide companies (Sandvik, Kennametal, Iscar, Mitsubishi Materials, and Ceratizit) in terms of raw materials, markets, recycling capabilities, and responses to tariff policies, drawing insights to propose strategic recommendations for China’s tungsten products industry.

Analysis of Major Global Tungsten carbide and Tungsten Product Companies

Dependence on Chinese Raw Materials

China accounts for ~85% of global tungsten ore production (International Tungsten Industry Association, 2024), serving as a critical raw material source for the Tungsten carbide industry.

Kennametal and Sandvik exhibit high dependence on Chinese tungsten raw materials (40% and 35%, respectively), making them significantly vulnerable to tariff measures. Both are accelerating efforts to diversify their supply chains.

Ceratizit has lower dependence (20%) and adopts a more flexible procurement strategy.

Global trends suggest that China’s share in raw material supply may decline by an average of 10%-15% by 2026. However, complete substitution remains difficult in the short term, underscoring the strategic value of China’s tungsten resources.

Dependence on the Chinese Market

China constitutes ~30% of the global cutting tools market (China Machine Tool & Tool Builders’ Association, 2024), with annual growth of 15% driven by aerospace and new energy demand.

Sandvik and Mitsubishi Materials rely heavily on the Chinese market (15%-20%), but their localized production in China helps mitigate tariff impacts.

Kennametal and Ceratizit have lower dependence (10% and 8%, respectively), enabling easier shifts to Southeast Asian and European markets.

China’s market size is RMB 60 billion. If tariff issues persist long-term without significant improvement, foreign companies may accelerate local production, threatening domestic market share.

Chart1.Localized Production Facilities of Major Enterprises in China

Tungsten Scrap Recycling Capacity and Recovery Rate

Globally, tungsten scrap recycling accounts for 30% of total supply (ITIA, 2024).

Chart2.Recycling Capacities of Major Enterprises

Opportunities and Challenges for China’s Tungsten Products Industry

Analysis of global companies reveals both opportunities and challenges for China’s tungsten products industry, forming the fundamental development logic for our country’s tungsten product supply chain strategy.

Breakthrough Technological Bottlenecks to Capture High-End Markets

The high-end cutting tool market offers a profit margin of 30%, far exceeding the 10% margin in the low-end segment. Compared to foreign technologies like Sandvik’s CoroPlus?, China’s technological gap remains significant. Therefore, accelerating innovation is imperative. The government should provide higher R&D tax incentives (e.g., 30%) to encourage capable enterprises to increase R&D investment (e.g., 5% of revenue). Efforts should focus on developing nano-grade tungsten powder, high-performance coated tools, AI-optimized processing technologies, and high-end customization.

Collaborations between companies like China Tungsten & Hightech (Zhuzhou Cemented Carbide) and Xiamen Tungsten (Xiamen Golden Egret) with institutions such as Tsinghua University, Central South University, and Xiamen University can advance low-cobalt alloy development to reduce production costs. Enterprises should adopt Iscar’s modular tool approach, introducing replaceable toolhead systems to lower customer replacement costs.

China should aim to increase its high-end cutting tool market share from 20% to 35% by 2028–2030, generating annual revenue growth of approximately RMB 200–250 billion. This expansion would cater to demands in aerospace (e.g., C919, C929, fifth- and sixth-generation aircraft, drones), low-altitude economy, and new energy (battery and automotive tools/molds).

Optimize Global Layout to Mitigate Trade Barriers

Current tariff tensions may compress export volumes and profit margins. Following the examples of Kennametal (Mexico factory) and Iscar (India expansion), overseas expansion is critical. China should encourage Xiamen Tungsten and Zhuzhou Cemented Carbide to establish factories in Vietnam and India to capture more overseas capacity and markets, producing low-cost tools (estimated 15% price reduction). Additionally, securing tungsten ore agreements with Brazil, Central Asia, and Mongolia could lock in 10% of global raw material supply and primary smelting capacity. Exploring assembly plants in Mexico under USMCA’s low tariffs would facilitate entry into the North American market (25% of global tool demand).

The government should introduce overseas M&A incentives (e.g., 50% investment subsidies) and resource development support (e.g., low-interest loans) to help acquire tungsten mines in Australia/Canada or European toolmakers (e.g., small coating technology firms). Synergies with domestic supply chains, such as CATL’s European plants, should be leveraged.

This strategy capitalizes on low-cost regions (Vietnam’s 20–50% cheaper labor) and high-growth markets (Southeast Asia’s 10% annual growth), boosting export profits and raising Southeast Asia’s market share from 15% to 20%+. It also facilitates local resource development and recycling of tungsten scrap.

Promote Tungsten Scrap Recycling to Build a Green Supply Chain

China’s tungsten recycling rate is alarmingly low, wasting 5,000 tons annually and incurring 30% higher costs. Learning from Ceratizit (45% recycling rate) and Sandvik (40%), China must act under the Solid Waste Law (2020) and Restricted Waste Import List (2020), which currently limit tungsten scrap imports. Domestic scrap collection rates are only 20%, hindering circular economy goals. Recommendations:

Ease Scrap Import Restrictions: Revise policies to allow imports with strict environmental monitoring.

Expand Domestic Recycling: Build recycling hubs in Hunan (Zhuzhou), Jiangxi (Ganzhou), Xiamen (Longyan), and Hebei, adopting zinc/chemical methods to achieve a 30% recycling rate by 2028.

Adopt 3D Printing: Reduce tool costs through additive manufacturing.

Increase R&D Investment

Establish a National Tungsten Recycling Laboratory with Central South University to develop electrochemical methods (target: 50% recycling rate). Encourage enterprises to allocate more revenue to R&D.

Introduce Tax Incentives

Reduce corporate income tax for recyclers, subsidize green equipment, and build a scrap collection network covering 80% of tool manufacturers. Align with carbon neutrality goals (2060).

Foster Industry Collaboration

Partner with COMAC (aviation) and CRRC (rail) to develop customized tools (e.g., composite materials for aerospace, rail processing), targeting 50% market share by 2027–2030. Expand mid-to-high-end capacity while serving SMEs and overseas low-end markets.

Advance Smart Manufacturing

Promote industrial IoT, big data centers, and AI-driven design (e.g., high-entropy tungsten alloys) to leverage China’s institutional and resource advantages.

Strengthen Global Cooperation

Collaborate with Japan/Korea on semiconductor-grade tools to dominate Asia’s high-end market.

Host international trade fairs and lead ITIA to shape global standards.

Establish an Industry Fund

Create funds (e.g., Jiangxi/Hunan governments + SSE) to balance supply-demand, fulfill national reserves, and counter foreign capital control.

Conclusion

Global leaders like Sandvik and Ceratizit thrive on diversified supply chains, localized production, and high recycling rates—exposing China’s gaps in technology, recycling, and global strategy. By prioritizing tech breakthroughs, recycling optimization, and overseas expansion—while fostering partnerships with aviation/rail sectors—China can secure its position as a tungsten resource, production, and recycling powerhouse. Liberalizing scrap imports and upgrading recycling tech will solidify this leadership, ensuring long-term dominance in the global tungsten industry.

Fracture Process

The fracture and separation of materials during metal cutting constitute a complex dynamic process involving multiple physical mechanisms. Research indicates that this process primarily consists of three key stages:

Plastic deformation occurs first. Crack initiation and propagation follow. Finally, material separation is achieved.

Based on extensive experimental data and theoretical analysis, this phenomenon can be systematically explained as follows:

Fracture Types and Mechanisms

According to material response and processing conditions, fracture can be divided into the following categories:

Shear fracture

Dominant type, where shear bands form at the tool-workpiece contact surface, and material separates along slip planes. For example, pure shear fracture is common in highly plastic materials (such as low-carbon steel), with fracture surfaces appearing wedge-shaped; microvoid coalescence fracture achieves separation through microvoid nucleation and aggregation.

Tensile fracture

At the tool’s leading edge or chip’s free surface, material forms tear ridges due to tensile stress, mostly occurring in brittle materials or under high cutting speed conditions.

Cleavage fracture

Under low temperature or impact loading, cracks rapidly propagate along specific crystal planes (cleavage planes), producing flat and shiny fracture surfaces, commonly seen in body-centered cubic metals (such as ferritic steel).

Basic Stages of Fracture

The fracture in metal cutting can be divided into three stages:

Crack initiation: When the tool contacts the workpiece, localized stress concentration leads to the formation of microcracks inside or on the surface of the material. For example, in the first deformation zone (chip formation zone) during cutting, the material undergoes slip deformation due to shear stress, thereby initiating cracks.

Crack propagation

As the tool advances, the crack extends along specific paths. The propagation direction is influenced by stress state and material properties, potentially manifesting as shear fracture (along the direction of maximum shear stress) or tensile fracture (along the direction of maximum normal stress).

Final separation

The crack penetrates through the material to form chips, and the resulting fracture surface may exhibit either ductile (fibrous) or brittle (crystalline) characteristics.

Dynamic Fracture in Cutting Process

Stage Division

Taking the cutting card theory illustrated in the following diagram as an example, the cutting process is divided into four stages: initial contact, crack initiation, material uplift, and cyclic phase. The crack initiation stage represents the critical point for fracture formation, while the cyclic phase involves periodic crack nucleation, resulting in saw-tooth shaped chips.

Deformation Zone Effects

Primary Deformation Zone (A-H region): Material undergoes intense shear deformation, forming initial cracks.

Secondary Deformation Zone (G-E region): Friction between chip and tool causes additional plastic deformation, potentially accompanied by localized fracture.

Tertiary Deformation Zone (E-D region): Workpiece surface material fractures due to tool flank face compression, forming the machined surface.

Key Influencing Factors

Tool Parameters: The tool’s rake angle, clearance angle, and major cutting edge angle affect stress distribution. For example, increasing the major cutting edge angle reduces cutting forces but may alter crack propagation paths.

Cutting Speed

Low speed → Ductile fracture; High speed → Brittle fracture (thermal softening effect reduces material strength).

Feed Rate

Large feed increases cutting thickness, promoting fracture (as utilized in chip breaker design).

Tool Rake Angle

Negative rake angle increases compressive stress, suppressing fracture; Positive rake angle intensifies tensile stress.

Edge Roundness Radius

Dull cutting edges enhance extrusion, easily inducing microcracks in brittle materials.

Clearance Setting

In shearing operations, the clearance between upper and lower blades (typically 5-10% of material thickness) controls crack meeting position. Improper clearance leads to increased burrs or rough fracture surfaces.

Material Properties

High ductility materials (e.g., aluminum) tend toward ductile fracture, forming fibrous fracture surfaces; Brittle materials (e.g., cast iron) readily exhibit cleavage or intergranular fracture.

Machining Conditions

High-speed cutting may induce adiabatic shear bands, causing periodic cracks and saw-toothed chips; Low temperature or alternating loads promote brittle fracture.

Material Characteristics

Performance in Actual Metal Cuttings

Chip morphology: Continuous cutting produces ribbon-like chips, while periodic fracture leads to saw-toothed chips.

Surface quality: Incomplete fracture generates burrs, whose height is positively correlated with clearance and material ductility. For example, excessive clearance significantly increases burr height.

Energy consumption: The fracture process requires overcoming material shear strength and plastic deformation energy; optimizing tool angles can reduce energy consumption.

Typical Case Analysis

Case 1: Crumbling Control in Cast Iron Cylinder Metal Cutting

Problem: Edge chipping occurs when cutting gray cast iron, and surface roughness exceeds standards.

Solution:

Switch to CBN tools (high hardness reduces compressive stress);

Use small feed rate (f = 0.1 mm/rev) and negative rake angle (?5°).

Case 2: Adiabatic Shear Fracture in Titanium Alloy Aerospace Components

Problem: Localized melting and adhesion of chips to the tool during cutting.

Solution:

High-pressure coolant to suppress temperature rise;

Optimize cutting speed to vc = 50 m/min.

Summary

Fracture in metal cutting results from the combined effects of mechanical response and metal cutting parameters. By controlling tool design (e.g., rake angle, clearance), optimizing cutting parameters (e.g., speed, feed rate), and considering material properties (e.g., ductility, fracture toughness), efficient and low-damage material separation can be achieved. Understanding fracture mechanisms is crucial for improving metal cutting quality, reducing burrs, and extending tool life.

When applied correctly, surface treatments can improve both the physical properties and functionality of machined parts. Since different types of CNC machining surface finishes involve distinct procedures and outcomes, understanding the fundamentals of these treatments is essential to determine the best option that meets the requirements of your intended application.

Why Do Machined Parts Require Surface Finishing?

CNC machining processes (including milling and turning) often leave visible cutting marks, which can compromise the surface quality of machined parts. Although CNC machining delivers precision components, these parts frequently require surface finishing for various reasons.

Why Surface Finishing Is Crucial for CNC-Machined Metal Parts:

Enhancing Appearance

Surface treatments such as sanding, polishing, electroplating, or painting help conceal sharp edges and machining marks left during CNC processing. As a result, these finishes enhance the visual appeal of CNC-machined parts.

Improving Corrosion Resistance

Most CNC-machined materials are susceptible to corrosive substances. To protect the surface of machined components and extend their service life, product designers often employ surface treatments like anodizing, polishing, and passivation.

Ensuring Hygiene & Cleanliness

Manufacturers apply various surface finishes to CNC-machined parts to ensure they are easy to clean and maintain. This is particularly critical in applications where hygiene is paramount, such as food processing equipment and medical devices.

Optimizing Fucctional Performance

Different CNC surface treatments are used to enhance material properties (e.g., conductivity), reduce friction, and add other desirable characteristics—improving overall functional performance.

Customization Options

By selecting the appropriate surface finish for your machined parts, you can customize them to meet specific preferences and requirements. A variety of finishes can be achieved to deliver desired surface properties, textures, or colors.

Common Types of Surface Finishes

Different surface treatments are suitable for various CNC machining materials, each with distinct surface roughness values. However, it is crucial to select the surface finish that best ensures optimal performance, functionality, durability, and visual appeal of the machined parts.

Below are the commonly used surface finishes for metal CNC-machined parts:

Polishing

Polishing is a classic mechanical finishing process that uses chemical agents or abrasives to create a highly glossy, mirror-like surface on metal parts. This finishing technique enhances the physical properties of machined metal components, improves corrosion resistance, ensures better cleanliness, and reduces friction.

Polishing is particularly suitable for metals such as aluminum, stainless steel, and brass. It is widely adopted by product designers and manufacturers in the food processing, medical, and luxury goods industries due to its functional and aesthetic benefits.

Although polishing can produce a smooth, reflective surface that enhances visual appeal, the process can be time-consuming and labor-intensive. This is especially true for machined parts requiring extremely high finishes or those with complex geometries.

Electroplating

Electroplating is a finishing process that involves depositing a layer of metal coating onto machined parts to increase their thickness. Applying this surface treatment to CNC-machined components protects them from corrosion, impact, high temperatures, and rust, ensuring long-term durability. This process is most suitable for metals such as chromium, cadmium, tin, copper, nickel, and gold. Electroplating enhances adhesion between the substrate and its external coating while also enabling machined parts to acquire magnetic or conductive properties depending on the plated metal.

Unlike other CNC surface treatments, electroplating is not environmentally friendly due to its generation of hazardous waste. Improper handling can lead to significant pollution. Additionally, electroplating is time-consuming and relatively expensive, requiring specialized equipment, metals, and chemicals—especially when multiple layers are needed on metal components.

Passivation

Passivation protects ferrous materials like steel and stainless steel from corrosion and rust, improving appearance, performance, and cleanliness. This chemical treatment involves immersing machined metal parts in acidic solutions such as nitric or citric acid to remove surface iron, resulting in a smooth, polished finish.

Since passivation is not a coating, it does not require masking or add thickness to the machined part. The acid bath eliminates traces of iron and rust from the surface, forming a protective layer composed of chromium or nickel. While nitric acid is the traditional choice for passivation, citric acid baths have gained widespread acceptance due to their shorter processing times.

Passivated parts exhibit excellent rust resistance, making them ideal for outdoor applications. Moreover, passivation is widely used across industries—from aerospace (requiring high-quality steel and tight tolerances) to medical sectors (where sterilization and longevity are critical).

However, passivation may extend production lead times because machined metal parts must undergo pretreatment, such as cleaning to remove debris, grease, or other contaminants. While immersion is the most common passivation technique (offering faster cycles and better consistency), acid spraying serves as a viable alternative.

Anodizing

Anodizing creates a protective oxide layer on the surface of machined metal parts. This coating shields the metal from corrosion and wear while being compatible with various colors. It is non-conductive and highly durable (Type III). Anodizing is ideal for forming corrosion-resistant coatings on aluminum and titanium components.

To anodize a CNC-machined metal part, it is immersed in a diluted sulfuric acid solution, and an electrical current is applied between the part (anode) and a cathode. This triggers an electrochemical reaction, converting the exposed surface into hard titanium or aluminum oxide. However, critical features like threaded holes—which must remain conductive—should be masked before anodizing.

Anodized parts can be dyed in colors such as gold, red, black, or blue before sealing. The coating’s thickness and density can be adjusted by varying the anodizing time, consistency, and duration. There are three primary anodizing variants, each with distinct processes, coating thicknesses, and properties:

Type I (Chromic Acid Anodizing)

Produces the thinnest layer, preserving part dimensions.

Results in a grayish finish that cannot be dyed.

Type II (Boric-Sulfuric Acid Anodizing)

A safer option with better paint adhesion, allowing for color customization.

Known as “decorative” or standard anodizing, with coatings up to 25 μm thick.

Type III (Hardcoat Sulfuric Acid Anodizing)

The most common type, especially for aluminum and titanium alloys.

Provides the clearest surface, enabling the widest color compatibility.

Coating thickness ranges from 0.001 to 0.004 inches (25–100 μm).

Combined with PTFE/Teflon, it forms a dry lubricated surface.

Alodine

Alodine or chem film is the brand name for chromate conversion coating. This chemical surface treatment requires immersing machined components in a proprietary chemical solution primarily composed of chromium. When selecting Alodine treatment for metal CNC machined parts, please ensure the process complies with the MIL-DTL-5541F standard. This standard specifies the technical requirements for chemical conversion coatings on aluminum and aluminum alloys in U.S. military specifications.

The Alodine protective coating effectively inhibits corrosion. More importantly, it can be used in conjunction with decorative surface treatments as it significantly improves the adhesion of paints and adhesives. Unlike other surface treatments that reduce the thermal and electrical conductivity of aluminum parts, Alodine actually enhances the electrical conductivity of aluminum components. This surface treatment method is relatively low-cost, but its coating is more prone to scratches and surface damage.

Coating

Powder coating is an electrostatic process that applies dry powder to form a thin, uniform protective layer on the surface of CNC-machined parts. This technique is compatible with all metals and enhances the strength, corrosion resistance, and wear resistance of the components.

Unlike anodized metal parts, powder-coated metal parts exhibit superior impact resistance and are available in a wide range of colors. The process can be combined with sandblasting to produce machined parts with smooth, uniform surfaces and exceptional corrosion resistance. The powders used can be either thermosetting or thermoplastic polymers.

Although similar to painting, powder coating involves applying dry powder to the metal part surface and curing it in an oven. For optimal corrosion protection, machined parts may first require a primer treatment, such as chromate conversion or phosphating. The parts are then coated with dry powder using an electrostatic spray gun and cured in an oven at 200°C (392°F). Multiple layers can be applied to achieve the desired coating thickness, typically ranging from 18 μm to 72 μm.

Electroplating

Electroplating is a finishing process that deposits a metallic coating onto machined metal parts to increase their thickness. This surface treatment enhances CNC-machined components by protecting them against corrosion, impact, high temperatures, and rust, significantly extending their service life. The process is most suitable for metals such as chromium, cadmium, tin, copper, nickel, and gold. Electroplating improves adhesion between the substrate and external coatings while also enabling customized properties—magnetic or conductive—depending on the plated metal.

Unlike other CNC surface treatments, electroplating is not environmentally friendly due to its generation of hazardous waste. Improper disposal can lead to severe pollution. Additionally, the process is time-consuming and relatively costly, requiring specialized equipment, metals, and chemicals—especially for multi-layer plating.

Passivation

Passivation protects ferrous materials (e.g., steel, stainless steel) from corrosion and rust, improving appearance, performance, and cleanliness. This chemical treatment involves immersing machined parts in acidic solutions (nitric or citric acid) to remove surface iron, resulting in a smooth, polished finish.

As passivation is not a coating, it requires no masking and adds no thickness to the part. The acid bath eliminates iron and rust residues, forming a protective chromium/nickel oxide layer. While nitric acid is the traditional choice, citric acid baths are now widely adopted for their shorter cycle times.

Passivated parts excel in rust resistance, making them ideal for outdoor applications. The process is critical across industries—from aerospace (demanding high-grade steel and tight tolerances) to medical (requiring sterilization-compatible surfaces).

However, passivation may extend lead times due to mandatory pre-treatment (e.g., cleaning to remove debris or oils). Immersion remains the most common method for its consistency, though acid spraying offers an efficient alternative for complex geometries.

Electroless Nickel Plating

The electroless nickel plating process involves forming a nickel alloy protective layer on CNC machined parts to enhance their corrosion resistance. It uses a nickel bath and chemical reducing agents (such as sodium hypophosphite) to deposit a nickel alloy coating (typically nickel-phosphorus) on metal components. This process uniformly applies the nickel alloy coating to complex parts with features like holes and grooves.

There are several types of electroless nickel plating, each with different phosphorus contents. These include low-phosphorus, medium-phosphorus, and high-phosphorus nickel.

Parts treated with nickel plating typically exhibit excellent hardness and wear resistance. Additionally, they can be made harder through heat treatment. The electroless nickel plating process is suitable for various metals, including stainless steel, aluminum, and steel.

Despite its significant advantages, this method has certain limitations, including:

Subsequent reduction in plating rate

Accumulation of contaminants in the nickel bath

Increasing phosphorus content

Furthermore, electroless nickel plating is less suitable for rough, uneven, or poorly machined surfaces.

Conclusion

Metal CNC machined parts can undergo any surface treatment to ensure they meet your project requirements. In this article, we have discussed the most common surface treatments for metal CNC parts, each with its unique advantages and disadvantages. We hope this helps you understand how these surface treatments work and their outcomes, enabling you to determine the most suitable surface treatment for your specific application.

Sources of Waste tungsten carbides

Globally, approximately 30,000 to 50,000 metric tons of waste tungsten carbides are generated annually, with China accounting for over 40% of this volume, indicating tremendous recycling potential. Specifically, waste tungsten carbides primarily originate from the following sources:

Residual materials from worn cutting tools, such as lathe tools, milling cutters, and drill bits;

Large tungsten carbide components, including mining drill bits, molds, and rolling mill rolls;

Certain wear-resistant electronic components (e.g., semiconductor packaging materials) that contain tungsten carbides.

Recycling Methods for Waste tungsten carbides

Currently, mainstream recycling technologies include mechanical, chemical, and zinc melting processes, each with its own advantages and limitations:

Crushing Method

The mechanical crushing method is one of the simplest approaches for recycling waste tungsten carbides. It does not alter the chemical composition of the waste material and does not require separation of tungsten and cobalt. After surface cleaning, the waste tungsten carbide undergoes mechanical crushing and ball milling to produce a mixed powder with a chemical composition nearly identical to the original waste (except for a slight increase in iron content and decrease in carbon content).

For tungsten carbides with low cobalt content (which tend to have relatively lower strength), the material can be manually or mechanically crushed to a certain fineness before being ground in a wet mill to achieve the desired particle size for reuse in tungsten carbide production.

Advantages:

Simple process, short workflow

Low energy consumption

Environmentally friendly (no chemical pollution)

Limitations:

Risk of contamination from metal tool debris during manual crushing

Ineffective for high-cobalt tungsten carbides due to their resistance to crushing

Difficulty in ensuring consistent quality for recycled products made from complex carbide mixtures

Advancements in the Crushing Method

Russian researchers have developed an innovative tungsten carbide?recycling process utilizing a simple mechanical crushing approach. This method employs a novel high-power crusher—the conical inertial crusher—enabling high-quality recovery of waste tungsten carbides through crushing and fine grinding alone, without requiring any chemical treatment.

For instance, when processing waste YG6 anvils (used in synthetic diamond production), the waste anvils are first crushed in the conical inertial crusher to produce raw material for tungsten carbide?manufacturing. To enhance the performance of the crushed powder mixture, it is recommended to add 1%–2% cobalt powder, which improves compaction and sintering densification.

Currently, the crushing method continues to evolve, with the adoption of more advanced, cleaner, and efficient crushing equipment for processing waste tungsten carbides.

Zinc Melting Process for tungsten carbide?Treatment

Fundamental Principles of the Zinc Melting Process

The mechanism of the zinc melting process for tungsten carbides is based on the formation of?low-melting-point carbides?between zinc and the binder-phase metals (cobalt or nickel) in tungsten carbides at?900°C. At?896°C, the solubility of cobalt in zinc reaches?27%, allowing the binder metal to separate from the tungsten carbide?and form a?zinc-cobalt solid-solution carbide?liquid. This disrupts the tungsten carbide’s structure, leaving behind a loosely bound?hard-phase skeleton.

Since zinc does not chemically react with refractory metal carbides, and given that zinc’s vapor pressure is significantly higher than cobalt’s at specific temperatures, zinc can be?evaporated and recovered (at 925°C)?for reuse. As a result, the carbide powder obtained through the zinc melting process retains most of its original properties. After the process, cobalt or nickel is extracted into the zinc melt, while the carbides remain. The zinc is then distilled off and recycled for subsequent reuse.

Traditional zinc melting furnaces?are?vertical vacuum furnaces. The system operates under conditions ranging from?vacuum to partial-pressure atmospheres, up to just below atmospheric pressure. The components of zinc melting equipment are illustrated in?Figure 2, while the furnace’s main structure is shown in?Figure 3.

Key Characteristics of the Zinc Melting Process

The zinc melting process was invented by the British in the 1950s. Subsequently, the United States improved this process and enhanced the equipment. After the 1970s, it became widely adopted in many countries. In China, many manufacturers engaged in recycling waste tungsten carbides have mastered this method. Its main advantages are simple process, short flow, simple equipment, small investment, and low cost, making it particularly suitable for processing waste tungsten carbides with cobalt content below 10% and applicable for small enterprises to reuse waste tungsten carbides for carbide reproduction.

However, this process also has some disadvantages. First, the residual zinc content in the mixed material is relatively high. During the zinc melting and zinc recovery processes, whether the equipment is reasonable or not affects the zinc recovery efficiency. Second, the entire process consumes a large amount of electricity, with power consumption for each ton of tungsten carbide reaching approximately 6,000~12,000 kW·h. Additionally, there are environmental protection issues, as zinc emissions may have certain impacts on operators.

Currently, China’s WC-Co carbides have three tungsten carbide grain structures: coarse, medium, and fine. P-type carbides can be roughly divided into three categories based on titanium content: low-titanium, medium-titanium, and high-titanium. During recycling, it is best to strictly separate them to avoid mixing different sizes of tungsten carbide grains or zinc-melted mixed materials with different titanium contents.

Electrochemical Methods

Electrochemical methods mainly include the electrolysis method, as well as the electrolytic electrodeposition method and the electrodialysis electrolysis method developed from the electrolysis method.

Each method offers unique capabilities for metal recovery and purification from tungsten carbide waste streams.

Principle of Electrolysis Method

The electrolysis method involves directly placing waste tungsten carbides into an electrolytic cell with acids (hydrochloric acid, sulfuric acid, nitric acid, etc.) as the electrolyte. During electrolysis, the Co in the carbide transforms into Co2? and enters the solution, while the WC, having lost its binder metal cobalt, becomes a porous carbide. The cobalt-containing solution is precipitated with ammonium oxalate, and cobalt powder is obtained after calcination and reduction. The WC can be directly used in tungsten carbide production after ball milling and crushing or appropriate treatment (such as post-crushing carbon supplementation and re-carburization).

The electrolytic electrodeposition method takes advantage of the fact that hydrogen’s deposition potential is more positive than that of cobalt, causing hydrogen gas to preferentially deposit at the cathode. As the Co2? concentration increases and H? decreases, metallic cobalt is simultaneously deposited alongside hydrogen at the cathode. Thus, the electrolytic system becomes an electrolytic refining process where waste carbide serves as the anode, CoCl? as the electrolyte, and pure cobalt is deposited at the cathode.

The electrodialysis electrolysis method introduces a cation-exchange membrane into the electrolytic cell, dividing it into anode and cathode compartments. The cation-exchange membrane, a functional polymer film selectively permeable to ions, allows only cations to pass while blocking anions. Consequently, Co2? migrates through the membrane into the cathode compartment during electrolysis, while OH? accumulates in the cathode compartment due to the membrane’s barrier effect, raising the pH and resulting in Co(OH)? precipitation. Compared to conventional electrolysis, both the electrolytic electrodeposition and electrodialysis electrolysis methods shorten the cobalt recovery process and improve recovery rates.

High-Temperature Treatment Method

Principle of High-Temperature Treatment

The high-temperature treatment process is a novel recycling technology for tungsten carbides. This method involves re-sintering tungsten carbides at high temperatures to loosen their structure and promote grain growth. Subsequent mechanical crushing yields high-quality powder suitable for producing coarse-grained tungsten carbides. tungsten carbides manufactured from this powder exhibit performance metrics that meet or exceed those of standard carbide products. The high-temperature treatment process provides a new approach for recycling waste tungsten carbides and producing coarse-grained tungsten carbides.

High-Temperature Treatment Process for Waste tungsten carbides

The high-temperature treatment of tungsten carbides is conducted in specially designed high-temperature furnaces. Under a protective atmosphere at temperatures exceeding 1800°C, the waste carbide undergoes treatment where binder metals like cobalt liquefy and boil, causing carbide deformation and significant volume expansion. The carbide structure transforms into a porous, honeycomb-like formation, making the hardened carbide extremely easy to crush and process. During this high-temperature treatment:

A substantial liquid phase forms in the carbide

Atomic diffusion intensifies→

WC dissolution-precipitation effects strengthen→

WC grains grow rapidly from 1-2μm to several dozen or even hundreds of micrometers→

Defects in WC crystal structures are eliminated during recrystallization→

WC crystal structures become more complete→

Trace metal/non-metal impurities and harmful contaminants are removed

Characteristics of High-Temperature Method and Regenerated carbide Performance

This regenerated mixed material is particularly suitable for producing coarse-grained, high-cobalt-content tungsten carbides. For fine-grained, low-cobalt carbides:

• Higher treatment temperatures are required to generate sufficient stress for expansion and porosity
• Modified preparation and sintering processes are necessary for medium-fine grain production

Processing steps:

Initial crushing of treated carbide

Ball milling to -180 mesh (80μm) for regeneration suitability

The recycled carbide powder is ideal for coarse-grained tungsten carbide production. Test results show:

• Physical-mechanical properties match those of virgin powder carbides
• Grain size increases by 1μm
• Service life of rock drilling buttons and cold heading dies improves by 20%

Advantages:

• Short process flow
• Simple equipment requirements
• Clean recycled mixed materials
• Low environmental pollution
• High recovery rates

Limitations:

• High energy consumption
• Some cobalt loss during high-temperature processing
• Recycled material only suitable for coarse carbide grain carbides

Currently used by manufacturers in industrialized nations like Japan and Sweden.

Conclusion

Waste tungsten carbide recycling represents not just economic resource reuse but a crucial component of green manufacturing. With advancing technology and policy support, the recycling industry will become more efficient and environmentally friendly, contributing to global sustainable development.

What’s more, industrial enterprises should establish classified recycling systems.Individual users should properly dispose of used tools/drill bits through professional recyclers

“Waste is just resources in the wrong place” – tungsten carbide recycling perfectly embodies this philosophy!

Phase Composition of WC-Co Cemented Carbides

Figure 1 shows the vertical section of the W-Co-C ternary phase diagram along the Co-WC line. Taking a WC-60%Co alloy as an example:

Before liquid phase formation, the solubility of WC in Co increases with temperature.

At the eutectic temperature (~1340°C), a liquid phase with eutectic composition begins to form in the sintered body.

During sintering at 1400°C and subsequent holding, the sintered body consists of a liquid phase and residual WC solid phase.

Upon cooling, WC first precipitates from the liquid phase. Below the eutectic temperature, the WC-based carbides forms a two-phase structure of WC + γ.

Figure 1: Vertical Section of the W-Co-C Ternary Phase Diagram Along the Co-WC Line

In actual production, the composition of sintered bodies often deviates from the vertical section of the Co-WC line. Consequently, the alloy is not simply composed of γ+WC two phases. As shown in Figure 2 , the carbon-rich side of the γ+WC two-phase region borders the γ+WC+C three-phase region and the γ+C two-phase region, while the carbon-deficient side borders the γ+WC+η three-phase region. Only when the carbon content of the sintered body varies strictly within the γ+WC two-phase region can the WC-based carbide avoid the formation of a third phase. Otherwise, it may lead to carbon inclusions or the formation of carbon-deficient η phase.

Since the strength of the alloy is closely related to the structure and composition of the γ phase, while the presence of η phase may degrade toughness, extensive research has been conducted on the γ and η phases, as well as phase transformation processes, in an effort to control the phase composition of WC-Co alloys and improve their overall performance.

γ Phase Composition and Phase Transformation in WC-based carbides

As shown in Figure 2, the composition of the γ phase depends on the carbon content of the alloy, while its tungsten content increases with decreasing carbon content. When the alloy’s carbon content lies at the boundary between the γ+WC two-phase region and the γ+WC+η three-phase region, the γ phase exhibits the highest tungsten concentration. Conversely, when free carbon is present and the carbon content aligns precisely with the Co-WC cross-section (i.e., the theoretical carbon content of 6–12 wt.%), the γ phase contains the lowest tungsten concentration.

The tungsten concentration in the γ phase is also influenced by the cooling rate: slower cooling results in lower tungsten content, while rapid cooling leads to higher tungsten retention. This occurs because faster cooling suppresses the diffusion-driven precipitation of tungsten from the γ phase, locking in a non-equilibrium concentration. Additionally, higher sintering temperatures increase the tungsten solubility in the liquid phase, thereby raising the tungsten content in the γ phase at a given cooling rate. However, under sufficiently slow cooling, thermodynamic equilibrium dictates that the γ phase composition becomes independent of the sintering temperature.

In WC-Co cemented carbides, the γ phase is a cobalt-based solid solution of W and C. It exists either as discrete γ grains separated by grain boundaries or as isolated γ domains unevenly distributed within the matrix. Both γ grains and domains typically exhibit equiaxed or near-equiaxed morphologies. Notably, the volume fraction of γ domains increases with higher cobalt content in the WC-based carbide.

Factors Influencing γ Phase Transformation in WC-based carbides

Effect of Internal Stresses

The mismatch in thermal expansion coefficients between WC phase (384×10??/°C) and γ phase (1.25×10??/°C) generates microstructural stresses during cooling (tensile in γ phase, compressive in WC phase).

Increased cooling rate or quenching suppresses W diffusion precipitation in γ phase, elevating W concentration in room-temperature γ phase while reducing hcp γ phase content.

Cryogenic treatment (below Ms point) induces W supersaturation in γ phase, enlarging the free energy difference between fcc and hcp γ phases. Concurrently, enhanced internal stresses promote Ms transformation, markedly increasing hcp γ phase fraction—particularly pronounced in low-Co alloys.

Impact of Cobalt Content

In low-Co alloys (e.g., WC-8Co), thin γ phase layers (<0.3 μm) facilitate W diffusion to WC grains, lowering W concentration in γ phase. This raises the Ms point, favoring hcp γ phase formation during cooling and yielding higher room-temperature hcp γ phase content.

η Phase in WC-based carbides

Formation Mechanism and Morphology of η Phase

Due to the narrow carbon content range in the WC-γ two-phase region (Fig. 2), carbon deficiency in raw materials or sintering decarburization often leads to η phase formation (e.g., M?C-type Co?W?C, Co?W?C, and M??C-type Co?W?C). Among these, Co?W?C is most common.

Formation process

Heterogeneous nucleation: γ phase nucleates along WC-γ interfaces using WC grain surfaces as nucleation sites, facilitated by slow W diffusion from WC to γ phase and high W concentration at phase boundaries. γ phase tends to fill surface defects (high-energy sites) of WC grains.

Carbon loss and η phase precipitation

Rapid C diffusion in γ phase causes C depletion when WC dissolves, resulting in W/C ratio imbalance (room temperature [W]/[C]≈284).

During sintering (1350-1500°C), excessive C loss leads to W-rich γ phase, precipitating carbon-deficient η phase (intermediate phases like Co?W and Co?W?C form first, transforming to η phase at high temperatures).

Phase equilibrium and morphology

η phase growth consumes W and C, driving WC dissolution until equilibrium is reached.

η phase morphology is influenced by γ liquid phase flow (e.g., cross-shaped single crystals).

Key point: Carbon imbalance is the primary cause of η phase formation, with γ phase nucleation dependent on WC interfaces and high-temperature C loss driving η phase precipitation.

Factors Influencing η Phase Formation

Carbon content is critically important for η phase formation. In the WC+γ+η three-phase region:

Higher carbon content maintains W and C concentrations in γ phase closer to equilibrium, hindering η phase nucleation.

Mild carbon deficiency: η phase growth relies on dissolution of WC microcrystals in γ interlayers, resulting in η phases enveloping undissolved WC grains with regular geometries.

Severe carbon deficiency: Significant deviation from equilibrium W/C ratio in γ phase promotes extensive WC dissolution, leading to dispersed particulate η phase distribution.

Cobalt content effects

High-Co alloys contain more γ phase with better fluidity, facilitating W and C diffusion. While η phase nucleation is difficult, growth is easier, forming coarse, clustered grains.

WC grain size effects

Coarser WC grains promote η phase nucleation but slow growth, resulting in dispersed particulate phases.

Sintering process effects

Faster cooling reduces dwell time at η phase critical temperature, suppressing η phase formation.

Higher sintering temperatures increase γ liquid phase quantity, favoring coarse η phase grains, but excessive temperatures may keep γ liquid away from η phase boundaries, inhibiting η phase growth.

Conclusions

A comprehensive understanding of the phase transformation processes during the sintering of WC-based carbides is crucial for optimizing production processes, controlling phase composition and microstructure in the alloys, thereby creating favorable conditions for manufacturing high-performance WC cemented carbides.

The primary functions of binders in cemented carbide manufacturing

In the powder metallurgy of cemented carbides, binders (also called forming agents) play critical roles, including:

Improving Powder Flowability

Reduces interparticle friction, enabling homogeneous mold filling and uniform compaction.

Prevents powder segregation (e.g., separation of WC and Co).

Enhancing Green Strength

Provides sufficient “green strength” to prevent cracking or edge chipping during handling or demolding.

Minimizes elastic aftereffects (post-compaction expansion).

Lubricating the Mold

Reduces friction between powder and die walls, lowering compaction pressure and extending mold life.

Improves surface finish and minimizes defects (e.g., delamination, cracks).

Facilitating Debinding

Must be fully removable (via thermal decomposition or dissolution) before sintering to avoid carbon residue or impurities that degrade alloy properties.

Performance Requirements for Binders
The binder must possess the following characteristics:

Excellent Compatibility

Uniformly mixes with WC-Co powders without agglomeration or sedimentation.

Chemically inert to powders (e.g., no oxidation of cobalt).

Suitable Melting Point and Viscosity

Melting point must align with compaction temperatures (typically room temperature to 100°C) to ensure:

Liquid-phase homogeneity during mixing.

Solid-phase strength during pressing.

Too high moderate viscosity leads to impedes powder flow.

Too low moderate viscosity leads to insufficient binding force.

High Binding Capacity and Lubricity

Binding capacity: Ensures green strength (flexural strength typically ≥5 MPa).

Lubricity: Reduces compaction pressure (e.g., from 600 MPa to 400 MPa).

Controlled Debinding Behavior

Broad debinding temperature range (e.g., 150–500°C) to prevent cracking from rapid volatilization.

Low carbon residue after debinding (<0.1%) to avoid disrupting alloy carbon balance.

Environmental and Safety Compliance

Non-toxic, low volatility (e.g., water-soluble PEG outperforms solvent-based rubber binders).

Meets industrial emission standards (e.g., sulfur- and chlorine-free).

Cost-Effectiveness

Low-cost and readily available (e.g., paraffin wax is more economical than rubber).

Recyclable or easy to dispose of (e.g., PEG can be water-washed and recovered).

Types of Binder

When manufacturing cemented carbide products, selecting the right binder is crucial for quality and efficiency. Here’s a detailed comparison of the three most common binder types to help you make the best choice for your application.

Paraffin Wax

Characteristics:Composition: Hydrocarbon-based, solid at room temperature with low melting point (50-70°C)

Best for: Small, simple-shaped carbide products

Advantages:

Excellent lubricity reduces die friction

Low debinding temperature (200-400°C) simplifies processing

Cost-effective and readily available

Limitations:

Lower green strength (prone to cracking)

Potential carbon residue during high-temperature debinding

Temperature-sensitive – requires dry storage

Pro Tip: Ideal for mass production of standard inserts where cost is key.

PEG (Polyethylene Glycol)

Characteristics:Composition: Water-soluble polymer with adjustable molecular weight (PEG-2000/4000)

Best for: Complex-shaped tools and precision molds

Advantages:

Higher green strength for intricate shapes

Water-soluble – enables aqueous pre-debinding

Minimal carbon residue

Limitations:

Hygroscopic – requires humidity control

Narrow debinding window (200-300°C)

More expensive than paraffin

Pro Tip: The go-to choice for premium cutting tools requiring precision.

Rubber (SBR, etc.)

Characteristics:Composition: Polymer elastomer requiring organic solvents (e.g., acetone)

Best for: Large, high-density components like rolls and mining tools

Advantages:

Highest green strength

Excellent elasticity prevents cracking

Limitations:

Challenging debinding (500°C+)

Potential sulfur contamination

Environmental concerns with solvents

Highest cost

Pro Tip: Reserved for specialized applications where extreme strength is critical.

Compatibility Principles Between Binders and Wet Milling Media

Paraffin Wax

• Requires organic solvents (e.g., ethanol, acetone)
• Limited solubility in ethanol alone – heating often needed

Recommended Medium: Ethanol + 10-20% acetone (enhances solubility)

PEG (Polyethylene Glycol)

• Excellent water solubility
• Requires oxidation protection for cobalt

Recommended Medium: Deionized water + 0.5% antioxidant (e.g., oxalic acid)

Rubber Binders

• Only soluble in strong organic solvents

Recommended Medium: Pure acetone (requires sealed system to prevent evaporation)

Performance Comparison of Three Major Binder Systems

Binding Strength

Rubber binders provide the highest strength due to their polymer chain structure, making them suitable for large compacts. PEG offers moderate strength ideal for complex geometries, while paraffin wax has the lowest binding strength as it relies solely on physical bonding.

Debinding Process

Paraffin wax can be removed at relatively low temperatures between 200 to 400°C, though carbon balance must be carefully controlled. PEG requires aqueous pre-debinding followed by thermal cycling, but is sensitive to moisture. Rubber binders demand high-temperature pyrolysis above 500°C and carry risks of sulfur contamination.

Residue Effects

Paraffin may leave carbon residues that affect the WC/Co ratio, requiring adjustment of carbon potential during sintering. PEG leaves virtually no residue, making it excellent for high-purity alloys. Rubber can leave sulfur residues that reduce the alloy’s corrosion resistance.

Economic Considerations

Paraffin wax has the lowest initial cost but may incur additional expenses for carbon management. PEG provides the best value for precision components and mass production. Rubber is the most expensive option and is only justified for specialized heavy-duty applications.

Selection Summary

For cost-sensitive production where simple processes are preferred, paraffin wax is suitable but requires careful control of dimensional stability during debinding. When high precision and environmental considerations are priorities, PEG is the optimal choice though it needs humidity-controlled storage. Rubber binders are reserved for applications requiring maximum strength and large components, provided that high-temperature debinding equipment is available.

Modern developments are creating hybrid binder systems that combine the advantages of these materials, such as PEG’s performance with paraffin’s cost benefits through advanced formulation techniques.

Contamination

Characteristics: Contamination is characterized by the presence of unevenly sized pores inside the cemented carbide product, with corresponding surface protrusions or holes.

If the surface is slightly contaminated and can be machined without leaving holes, the product can be considered qualified and released.

If the surface is severely contaminated or exhibits blistering, it should be classified as scrap.

Causes of Contamination

During the high-temperature sintering stage, gases generated by internal reactions in the sintered body escape or migrate to the surface. By this time, the liquid phase has already begun to solidify, leaving behind small pores that cannot recover in time, and the gases migrating to the surface are not completely expelled.

Certain difficult-to-reduce oxides are only reduced at the temperature where the liquid phase forms. The pressure of the gases produced by reduction exceeds the resistance of the liquid phase contraction, leading to blister formation.

1.Excessive temperature (over-sintering) causes a significant increase and aggregation of the liquid phase, resulting in blistering.

2.Impurities in the pressed blocks, such as carbide chips or copper wires, can also cause blistering (contamination).

3.Severe delamination in the pressed product can also manifest as blistering during sintering.

Sources of Contamination

1.Oxidized block materials, oxidized granular materials, and defective pressed blanks.

2.Metal impurities: Screen mesh debris, cobalt chips.

3.Non-metal impurities: Ceramic fragments, glass fragments, boat-filling materials, dust, brush debris, etc.

4.Forming agents: Unremoved mechanical impurities, unfiltered gel, uneven forming agents, aged forming agents, etc.

Deformation

Characteristics: The geometric shape of the carbide product undergoes irregular changes, and warped products exhibit a regular curved deformation on a specific plane.

For such deformedcarbide products, inspections should be conducted according to standards or product drawings. Products that exceed tolerance limits should be returned to the production unit for reprocessing, and those that cannot be reprocessed should be classified as scrap.

Causes of Deformation Defects

1.Uneven density of the pressed product: This leads to uneven shrinkage during sintering. Areas with higher density shrink less, while areas with lower density shrink more.

2.Uneven carbon atmosphere around the pressed blank: This causes deformation of the product.

3.Uneven temperature environment during sintering: The pressed blank deforms due to temperature inconsistencies in the sintering environment.

4.Other reasons: Improper loading of the sintering boat, uneven placement of the base plate, etc.

Peeling

Characteristics: Peeling is characterized by the appearance of irregular branch-like cracks, cracks, or flaking at the edges and corners of the alloy product. In mild cases, it presents as a network of cracks, while in severe cases, small pieces may peel off. In extreme cases, the product may crack and peel off entirely, with cotton-like carbon black deposits clearly visible at the peeling sites. Carbide products with peeling are directly classified as scrap.

Causes of Peeling

1.High concentration of carbon-containing gases in the low-temperature zone: High concentrations of carbon-containing gases penetrate weak areas of the product (such as edges and corners, which often have lower density or significant elastic aftereffects). Under the catalytic action of cobalt, carbon precipitation reactions occur:

CH=C+H 2

CO =?C+CO

The precipitated carbon disrupts the continuity of the carbide, leading to peeling. In other words, the decomposition of carbon-containing atmospheres into large amounts of free carbon is the primary cause of peeling.

2.Vacuum dewaxing stage: If the dewaxing temperature exceeds 400°C (typically 375°C), it reaches the pyrolysis temperature of paraffin, generating low-molecular-weight paraffin, olefins, and free carbon. As the temperature continues to rise, paraffin pyrolysis intensifies. At this stage, the sintered body becomes porous and loose, significantly reducing its strength and making it difficult to withstand the impact of hydrocarbon gases generated by paraffin pyrolysis, leading to peeling.

Process Parameters Affecting Peeling

(1) Boat pushing speed and heating rate in the low-temperature zone

(2) Moisture content in hydrogen

(3) Loading amount in the boat

(4) Catalytic effect of cobalt

Carburization

Carburized carbide products have a shiny, oily black surface, with fine graphite dots or nest-like spots visible on the cross-section. In severe cases, the product may feel lubricated to the touch and leave black marks. Carburization generally affects the performance of the product and should be evaluated based on the specific grade and intended use. Non-compliant products should be returned to the production unit for reprocessing.

Causes of Carburization

1.Excessive total carbon content in the mixture

2.High carbon content in the filler material

3.High concentration of hydrocarbons in the low-temperature zone atmosphere

4.Diffusion of carbon from graphite boats into the sintered body

Rapid heating rate and short duration during the removal of the forming agent, causing the forming agent to decompose and generate free graphite, leading to carbide carburization

Sources of Free Carbon

1.Decomposition of the forming agent during the dewaxing (degumming) process

2.Diffusion of carbon from graphite boats

3.Control of the sintering atmosphere in the vacuum furnace

Decarburization

Decarburized carbide products exhibit white bright spots or shiny streaks on the surface, with silver-white shiny spots or tadpole-shaped pits visible on the fracture surface. The microstructure may show the presence of the η phase. Decarburization generally affects the performance of the product, and decarburized carbide products should be returned to the production unit for reprocessing.

Causes of Decarburization

1.Decarburization reaction during hydrogen sintering

The reaction between WC in the product and H? generates CH?. This reaction occurs throughout the sintering process and intensifies as the temperature rises.

At the furnace entrance, before complete shrinkage, decarburization occurs both internally and externally in the product.

At the furnace exit, after the product has shrunk, decarburization occurs on the surface. The intensity of the reaction depends on the flow rate of H?. The CH? generated by this reaction decomposes at high temperatures, causing carburization of the product.

Moisture in the furnace atmosphere reacts with WC or C at temperatures above 825°C:

H2O+WC→W+H2+CO

H2O+C→CO+H2

This reaction also occurs at both the entrance and exit of the furnace. Before complete shrinkage, it causes internal and external decarburization, while at the furnace exit, it causes surface decarburization.

Decarburization reaction during vacuum sintering

The deoxidation reaction during vacuum sintering occurs because the pressed blank contains oxygen, which is reduced by free carbon and carbon in WC during sintering. The reactions are:

MeO+C→Me+CO

MeO+2C→MeC+CO

This reaction also occurs at both ends of the furnace entry and exit. Before complete contraction, the U-shaped product causes decarburization both inside and outside. At the exit end, it causes decarburization on the product’s surface.

2.Vacuum sintering decarburization reaction

The deoxidation reaction after vacuum sintering occurs because the compact contains oxygen, which is reduced by free carbon and carbon in WC during sintering. The reaction is: MeO + C == Me + CO, MeO + 2C == MeC + decarburization reaction has occurred.

Mixing

The surface of the alloy product mixed with materials resembles the skin of a bitter melon, with uneven alloy structure. Its cross-section is different from the general dirty holes, often showing spots of varying sizes and shapes, as well as uneven surfaces. Different grades of organizational structure can be seen in the microstructure. Mixed carbide materials affect performance and are generally considered scrap, but slightly mixed materials can be inspected and treated according to the standard for cross-sectional contamination.

Causes of mixing

1.Mixing before pressing

2.The influence of certain impurity elements, such as aluminum, sulfur, silicon, phosphorus, and boron, which can cause WC grain growth during liquid-phase sintering, with phosphorus having the most significant effect.

Over-sintering

Over-sintering products have enlarged surface grains and coarser cross-sectional structure. In mild cases, only a larger number of shiny spots are observed, while in severe cases, the surface sometimes shows blisters or a honeycomb appearance. Over-fired products should be considered scrap.

Causes of over-sintering

1.Excessive sintering temperature – grain growth

2.Prolonged holding time – grain growth

Under-sintering

Under-fired alloy products have a loose structure, dark surface color, and no metallic luster. Vacuum-sintered products have a gray-white surface, larger shiny spots on the cross-section, and a noticeable water absorption phenomenon. Under-fired products should be returned to the production unit for treatment.

Poor pressing

This type of alloy product, due to insufficient compacting density and excessively large hole size, does not completely disappear during the sintering process. The product’s surface shows loose particles, mainly appearing at the blade edges and corners. In severe cases, fine cracks appear on the surface, and the cross-section shows triangular or strip-shaped holes. If only the surface is slightly poorly pressed, and the cross-section and metallography do not show this phenomenon, it can be released as a qualified product. If the surface is poorly pressed, and the cross-section and metallography also show this phenomenon, then this type of product should be treated as scrap.

Causes of poor pressing

Overly hard, overly coarse granular materials, uneven distribution of granular materials in the mold cavity, low compact single weight, low pressing pressure, or local low density.

Conclusion

The above only analyzes several reasons for the non-conformance of carbide products. In actual production, there may be various other issues, which require us to further improve our understanding, analyze the causes, and propose specific countermeasures. After the occurrence of non-conformance, it is necessary to seriously analyze our production process, identify the causes, and make improvements. Generally, attention should be paid to details, especially the usual practices that are often taken for granted. Only by truly focusing on the details can we reduce problems and avoid quality issues. Therefore, it is said: “Details determine success or failure.”

Electrolytic Grinding of Carbides

Electrolytic grinding combines electrochemical machining and mechanical grinding to process carbides, with electrochemical machining playing the dominant role (80%-90%), while mechanical grinding accounts for only 10%-20%. The productivity of this method is 4-8 times higher than conventional mechanical grinding. Additionally, it allows for easy adjustment of electrical parameters, merging rough and fine machining into a single step, thereby shortening production cycles and reducing costs. This makes electrolytic grinding an ideal method for machining carbides.

Structure and Principle

Electrolytic grinding primarily consists of three main components: a DC power supply, a machine tool, and a hydraulic system, as shown in Figure 1.

During electrolytic grinding, the carbide?workpiece is connected to the positive pole of the DC power supply, while the diamond conductive grinding wheel is connected to the negative pole. A certain contact pressure is maintained between the two, and an electrolytic gap is preserved between the workpiece and the protruding abrasive particles (diamond) on the grinding wheel. Electrolyte is supplied into this gap. When the power is turned on, an electrochemical reaction occurs on the workpiece surface, causing the carbide?to electrolyze and form a thin oxide layer (electrolytic film) on its surface. This oxide layer is much softer than the carbide?itself. The high-speed rotating diamond grinding wheel continuously removes this oxide layer, which is then carried away by the electrolyte. This exposes a fresh surface of the workpiece, allowing the electrolytic reaction to continue. The alternation between electrolysis and oxide layer removal results in the continuous machining of the carbide, forming a smooth surface with precise dimensions.

Electrochemical Reactions in Electrolytic Grinding of Carbides

carbides are primarily composed of hard carbides (WC, TiC) with a metal binder (Co), formed through pressing and sintering. According to electrochemical reactions, cobalt begins to dissolve at 1.2V, forming Co(OH)?:

?

Tungsten carbide starts to dissolve at 1.7V, while titanium carbide begins to dissolve at 3.0V:

The electrolytic efficiency is the percentage of theoretical electrolysis to actual electrolysis. In electrolytic grinding, the electrolytic efficiency of carbides ranges from 70% to 90%.

Machining Parameters

Power Supply

The power supply for electrolytic grinding is a DC source with a voltage range of 4-14V and a current range of 50-3000A. The machining gap is approximately 0.03mm (roughly equal to the size of the abrasive particles).

Electrolyte

Electrolytic grinding is based on electrochemical dissolution. The choice of electrolyte significantly affects productivity, precision, and surface quality. After extensive testing, the following three electrolyte compositions were selected:

Electrolyte 2:

NaNO?: 6.3%, NaNO?: 0.3%, Na?HPO?: 2%, pH: 8-9, Na?B?O?: 1.4%, H?O: 90%

Electrolyte 3:

NaNO?: 5%, NaNO?: 1.6%, Na?HPO?: 1%, pH: 7-8, Na?B?O?: 1.5%, NaCl: 0.05%, C?H?(OH)?: 0.3%, H?O: Balance

The electrolyte is used at a temperature of 22-30°C and a pressure of 14-70kPa. The filter precision is 50-100μm, and the nozzle, installed close to the workpiece, is equipped with an air scraper.

Diamond Electrolytic Grinding Wheel

Diamond conductive grinding wheels are typically used for electrolytic grinding of carbides due to their regular shape, high hardness, and ability to maintain a consistent electrolytic gap, resulting in high productivity. During fine grinding, mechanical grinding can be performed independently. Diamond electrolytic grinding wheels can be categorized into metal-bonded and electroplated diamond wheels. The former is used for flat and cylindrical grinding of carbide?molds, while the latter is used for electrolytic form grinding of large batches of single-shaped workpieces and internal cylindrical grinding of small holes. The grinding pressure is generally around 30N/cm2. The linear speed of the grinding wheel is typically 1200-2100 m/min, and the contact length with the workpiece should not exceed 19mm to prevent electrolyte boiling.

Material Removal Rate and Precision

The material removal rate of carbides is proportional to the current density. Under specific alloy materials, electrolyte combinations, and electrolyte boiling points, the current density is limited by the anode dissolution rate. The productivity of electrolytic grinding of carbides is generally 0.16cm3 per 100 A/min. At a current density of 77.5A/cm2, the feed rate for face grinding is 25mm/min, with a typical dimensional accuracy of ±0.025mm per pass. If an additional mechanical grinding pass is performed without electrolysis, the accuracy can reach ±0.002mm. When grinding external contours, the corner radius on the workpiece is about 0.025mm, while the roundness radius for internal contours is limited to 0.25-0.38mm. The material removal rate in electrolytic grinding is 4-8 times higher than that of conventional grinding methods.

Surface Quality

The surface roughness achieved by electrolytic grinding of carbides is generally Ra 0.2-0.8μm, but it can reach Ra 0.025-0.1μm. The surface of the workpiece resembles that obtained by metallographic polishing, and the hardness of the workpiece does not affect the surface quality. During machining, the processed surface does not develop internal stresses or heat-affected zones, resulting in high surface integrity.

Equipment and Tools

The grinding machine must have sufficient rigidity to maintain precision even under a bending stress of 1 MPa between the grinding wheel and the workpiece. The machine requires corrosion-resistant accessories for pressurizing and filtering the electrolyte. Control equipment, fixtures, and mechanical and electrical systems should be made of suitable materials or coated to operate in a salt spray environment. Conductive diamond grinding wheels are preferred for electrolytic grinding, although non-conductive abrasive wheels can also be used, albeit with less effectiveness. The electrolyte nozzle is typically made of heat-resistant organic glass or equivalent insulating materials. Workpiece fixtures are made of copper or copper alloys. The design should ensure that the cathode and anode parts are insulated during electrolytic grinding to maintain proper machine operation.

Discussion of Key Process Parameters

Current Density and Voltage

In electrolytic grinding, current density is the primary factor determining productivity. Productivity increases with higher current density, but excessively high or low current densities can reduce machining precision and surface quality. In practice, voltage should not be increased indefinitely, as excessively high voltages can cause spark discharge, affecting surface quality. For carbide?electrolytic grinding, the optimal current density is 110 A/cm2, with practical current densities ranging from 15-60 A/cm2 and voltages from 7-10V. For rough grinding, the current is 120-300 A/cm2, while for fine grinding, it is 5-6 A/cm2.

Machining Gap

At a given voltage, a smaller machining gap results in higher current density, increased productivity, and improved surface flatness and precision. However, if the gap is too small, the electrolyte may not distribute evenly, leading to spark discharge and increased wheel wear. The typical machining gap is 0.025-0.05mm.

Grinding Pressure

Increasing grinding pressure enhances productivity, but excessive pressure reduces the electrolytic gap, increasing the risk of spark discharge. Conversely, insufficient pressure leads to incomplete removal of the oxide layer, reducing both efficiency and surface quality. Therefore, grinding pressure should be set to avoid spark discharge while ensuring complete oxide layer removal. The recommended grinding pressure is 0.2-0.5 MPa.

Contact Area Between Workpiece and Grinding Wheel

A larger contact area allows the DC power supply to deliver higher current, increasing productivity while maintaining good surface quality. Therefore, during electrolytic grinding, the grinding wheel and workpiece should maintain the largest possible contact area.

Grinding Wheel Speed

Increasing the grinding wheel speed ensures adequate and rapid electrolyte supply in the gap, enhancing mechanical grinding and productivity. However, the speed should not be excessively high. The typical linear speed of the grinding wheel is 1200-2100 m/min.

Electrolyte Supply

The electrolyte flow rate should ensure sufficient and uniform entry into the machining gap. For vertical electrolytic surface grinders, the flow rate is typically 5-15 L/min, while for cylindrical grinders, it is 1-6 L/min. The installation of the electrolyte nozzle is crucial, as it helps confine the electrolytic action to the machining gap between the grinding wheel and the workpiece. The nozzle must be firmly installed close to the outer surface of the grinding wheel and equipped with an air scraper to break the air layer on the rotating wheel’s outer edge. The electrolyte pressure is generally 14-70kPa, and the temperature is controlled between 19-33°C.

Conclusion

High Productivity

Electrolytic grinding of carbides offers 4-8 times higher productivity than conventional mechanical grinding, especially when the contact area between the conductive diamond grinding wheel and the carbide?workpiece is increased.

Excellent Surface Quality

Electrolytic grinding of carbides achieves high surface quality, with typical surface roughness of Ra 0.4μm or better, and can reach Ra 0.025μm, producing a mirror-like finish. Increasing the machining current does not significantly affect surface quality. Additionally, the processed surface does not develop internal stresses or heat-affected zones, resulting in high surface integrity unmatched by other machining methods.

High Precision

With advancements in carbide?electrolytic grinding, the use of diamond electrolytic grinding wheels that can perform both electrolytic and mechanical grinding allows for high precision. After electrolytic grinding, the power can be turned off, and mechanical grinding can be performed to achieve precision comparable to conventional mechanical grinding.

Low Grinding Wheel Wear

In electrolytic grinding, the abrasive particles in the grinding wheel primarily maintain the electrolytic gap and remove the oxide layer, reducing abrasive wear. The wear of diamond grinding wheels in electrolytic grinding is significantly lower than that in conventional mechanical grinding.

In summary, electrolytic grinding of carbides offers unique advantages over conventional machining methods, significantly improving productivity, surface quality, and precision, making it an ideal method for machining carbides.

Carbide Manufacturing Process

The process involves weighing ultra-fine WC powder and Co powder, produced by special methods, according to the composition ratio, and adding small amounts of elements such as Ti, Ta, Nb, and Cr. Wet grinding is performed using φ8 cemented carbide balls with a ball-to-material ratio of 5:1. The grinding medium is anhydrous alcohol, and the grinding time ranges from 72 to 120 hours. The slurry is dried at 80 to 100°C for about 2 to 4 hours, then mixed with glue (wax) to form granules. These are pressed into various products such as 5×5×30 and A118A, and sintered under H? protection at temperatures between 1400°C and 1500°C.

Microstructure and Physical-Mechanical Properties

Due to the use of special raw materials and production methods different from conventional processes, and the appropriate selection of types and quantities of added elements, the YT04 carbide achieves the desired effects. Table 1 lists the performance indicators of the YT04 carbide grade from several developments, and Figure 1 shows the metallographic structure of the YT04 carbide.

From the results in Table 1 and Figure 1, the YT04 carbide has high hardness and moderate strength. The microstructure is very uniform, with grain sizes almost all less than 0.5 μm, except for a few WC grains larger than 0.5 μm. The thickness of the binder phase is also less than 0.5 μm.

Cutting Characteristics

Application Range of YT04 carbide

Due to its extremely fine WC grain size and high hardness, the YT04 carbide has very high wear resistance, red hardness, and thermal strength, along with high strength. This carbide is suitable for machining difficult materials such as ferrosilicon, vanadium-titanium cast iron, boron-added cast iron, white cast iron, high, medium, and low nickel-chromium chilled cast iron; various quenched carbide steels, tool steels, magnetic steels, high manganese steels, ultra-high strength steels, high-speed steels; tungsten-based, molybdenum-based, titanium-based non-ferrous carbides; granite, marble, glass, cast stone, high-cobalt cemented carbide, steel-bonded cemented carbide, and some ceramic materials and engineering plastics for precision turning, milling, planing, and cutting. It can also be used for semi-finishing, with a durability 1 to 10 times higher than traditional YT, YG, and YM grade cemented carbides. The surface finish of the machined workpiece can reach up to ▽8. It shows particularly satisfactory results when used for low-speed cutting to replace high-speed steel tools.

Usage Conditions of YT04

According to relevant literature, the YT04 carbide should be used with the following parameters:

(1) Main cutting edge angle (K,) ≤ 45°.

(2) Rake angle (Y.) = 0 to -8°, cutting edge inclination angle (λ) = -5 to -9°.

(3) Clearance angle (a.) and tool nose radius (Ye). Since the YT04 carbide is only suitable for finishing and semi-finishing, a larger clearance angle should be chosen to reduce friction between the flank face and the workpiece surface, typically around 10°. The tool nose radius should be 1 to 2 mm.

(4) Cutting speed (V). The cutting speed should be determined based on specific conditions. For workpieces with HRC60 and above, a cutting speed of 10 m/min is ideal, and should not exceed 20 m/min to avoid tool tip reddening and burning. For materials around HRC45, the cutting speed can be increased to about 50 m/min, but should not exceed 100 m/min to fully utilize the tool’s excellent performance. For materials like 35CrMoA (HB≈229), the cutting speed can even be as high as 200 m/min or more.

(5) Depth of cut (αp). This depends on the surface quality requirements of the workpiece. For a finish of 76 or above, the cutting depth can be set at 0.07 to 0.12 mm. If the precision requirements are not strict, it can be set at 0.2 to 0.4 mm.

(6) Feed rate (f). YT04 is generally used for finishing, with a feed rate typically of 0.2 to 0.3 mm. For semi-finishing, the feed rate can be increased to 0.4 to 0.5 mm. It should be noted that if machining high-hardness materials around HRC65, too large a feed rate can cause chipping.

Cutting Examples

Here are some examples of YT04 carbide in practical use:

1. Material: Cast stone, workpiece size: Φ160×1500, external turning, tool geometry parameters: K,=45°, Y.=12°, α=6°, λ=-6°; cutting parameters: V=6 m/min, f=0.1 mm/r, ap=1.00 mm.
2. Material: Quenched bearing steel, HRC62, workpiece: Φ30×50 mm, external turning; tool geometry parameters: K=40°, Y.=15°, α.=10°, Re=0.5 mm. Cutting parameters: V=61.8 m/min, f=0.14 mm/r, αp=0.4 mm. Test results: After machining 11 pieces per cutting edge, the cutting path reached 2472 m, with basically no wear on the cutting edge, and a workpiece surface finish of 76.

Usage Instructions

1.Strictly follow the provided tool geometry parameters and cutting conditions.

2.YT04 carbide is not suitable for intermittent cutting.

3.YT04 carbide can be sharpened with green silicon carbide wheels. Using diamond oil stones for edge honing can further improve performance.

Conclusion

Overall, the YT04 carbide, with its extremely fine grain size and excellent physical-mechanical properties, performs exceptionally well in machining difficult-to-process materials and is suitable for various precision machining applications.

Sample Preparation and Experimental Conditions

Material Selection

To compare the corrosion resistance of WC-based cemented carbides, four groups of test materials were selected:
(1) WC-Co alloy;
(2) WC-Co alloy with a small amount of heterogeneous carbides;
(3) WC-Ni·Mo·Co·Cr alloy;
(4) Low binder phase content alloy.

Corrosion Conditions

Corrosion Media: Hydrochloric acid, sulfuric acid, nitric acid, citric acid (H?Cit), acetic acid (HAC), sodium hydroxide (50%), and potassium hydroxide (50%).
Test Temperatures: 20°C, 40°C, 80°C, and boiling point. Alkali solutions were only tested at the boiling point.
Corrosion Time: 24-72 hours for low temperatures and 6-24 hours for the boiling point.
Corrosion Rate Calculation: The corrosion rate (A) is calculated as the amount of material corroded per unit area per day, expressed in mg/dm2·day (abbreviated as mdd).

Results and Discussion

Relationship Between Corrosion Rate and Binder Phase Content in WC-Based Cemented Carbides

The corrosion rate of WC-based cemented carbides is related to the content of the binder phase, regardless of the binder’s composition. Alloys with higher binder content exhibit higher corrosion rates. For WC-Co alloys, when the cobalt content exceeds 2%, the corrosion rate increases sharply. In 5% HNO?, the corrosion rate of WC-2% Co alloy still exceeds the acceptable limit. However, the corrosion rate of WC-Ni·Mo·Co·Cr alloy with 2% Ni·Mo·Co·Cr meets the usage requirements under all tested conditions. Even in highly corrosive nitric acid, its corrosion rate is only 196.6 mdd, corresponding to corrosion resistance grade B (less than 250 mdd).

The difference in corrosion rates among alloys with varying cobalt content is not significant at room temperature. However, as the temperature increases, the difference becomes more pronounced. At room temperature, increasing the cobalt content from 2% to 20% results in a corrosion rate change of only 12-30 mdd. At the boiling point, the corrosion rate increases from 20 mdd for low cobalt content to 6×10? mdd for high cobalt content.

Effect of WC Grain Size on Corrosion Rate

Fine-grained alloys have higher interfacial energy and greater internal stress in the binder phase, resulting in lower corrosion resistance. Therefore, fine-grained alloys are not recommended for improving resistance.

Effect of Small Amounts of Heterogeneous Carbides on Corrosion Rate

Comparing WC-Co cemented carbides with small amounts of heterogeneous carbides reveals that their effects on corrosion rates vary:

Cr?C?: A small amount of Cr?C? can improve the alloy’s corrosion resistance. Even though alloy No. 9 has finer WC grains than alloy No. 4, its corrosion resistance is superior due to the addition of Cr?C?.

TaC: The addition of a small amount of TaC has no significant effect on resistance. Comparing alloy No. 4 with alloy No. 7 (which contains 2% TaC), the corrosion rates are similar. Adding 5% TaC also does not improve corrosion resistance.

Mo?C: Adding less than 1% Mo?C can significantly enhance resistance. This is because Mo?C readily dissolves in the γ phase, thereby improving the alloy’s corrosion resistance.

Thus, adding small amounts of Cr?C? or Mo?C is beneficial for improving the corrosion resistance of cemented carbides.

Effect of Graphite and η1 Phase on Alloy Corrosion Rate

The presence of graphite and η1 phase not only significantly affects the physical and mechanical properties of the alloy but also has a notable impact on the corrosion rate. For the tested media, the presence of graphite significantly reduces the alloy’s corrosion resistance. When graphite is present, the solubility of tungsten (or molybdenum) in the binder phase drops below 2-3%, reducing the binder phase’s resistance. Additionally, according to corrosion theory, graphite increases the electrochemical corrosion effect of micro-galvanic cells between phases. Therefore, cemented carbides used as corrosion-resistant materials must avoid the formation of graphite.

In contrast, the η1 phase significantly enhances the alloy’s corrosion resistance. The presence of η1 phase indicates carbon deficiency in the alloy, allowing the binder phase to dissolve a large amount of W (or Mo), typically 10-13%. This composition of the binder phase is more corrosion-resistant. Moreover, the transformation of a certain amount of binder into η1 phase further improves the alloy’s resistance. Thus, under carbon-deficient conditions, the alloy’s corrosion resistance increases sharply compared to normal alloys.

Given these findings, the carbon content should be controlled at the lower limit of the two-phase region or allow the formation of a small amount of dispersed η1 phase, provided that the mechanical properties are not excessively compromised. This results in an ideal microstructure with high corrosion resistance.

Relationship Between Binder Phase Corrosion Resistance and Alloy Corrosion Rate

While the mechanical properties of WC-Ni alloys are generally lower than those of WC-Co alloys, their corrosion resistance is superior, especially under low-carbon conditions. However, alloys with pure nickel as the binder often fail to meet usage requirements, leading to the development of complex nickel-based binders. Ni-Mo alloys exhibit excellent resistance to acid and alkali corrosion, making them suitable as binders for WC-based alloys. This study tested the corrosion resistance of alloys with Ni-Mo-Co-Cr (83:15:1:1) as the binder. The overall trend in corrosion rates for this series is similar to that of WC-Co alloys, but the values are significantly lower. Particularly, low binder content alloys meet the specified usage requirements for all tested media, with corrosion rates below 250 mdd. Additionally, the corrosion rate of WC-Ni·Mo·Co·Cr alloys does not change significantly with increasing temperature.

In summary, improving the corrosion resistance of WC-based cemented carbides depends on enhancing the binder phase’s corrosion resistance, which is particularly effective for low binder content alloys.

Activated Sintering of WC-Based Low Binder Content Alloys

An important approach to improving the resistance of WC-based cemented carbides is to reduce the binder content, provided that the physical and mechanical properties meet usage requirements.

To enhance the performance of sintered products, activated sintering is often employed. The properties of low binder content alloys are closely related to the uniformity of component mixing. Therefore, chemical mixing to produce composite powders, intensified ball milling, and activated sintering processes were adopted. For comparison, conventional processes were also used to prepare alloys with the same composition.

Comparison of Corrosion Resistance Among Different Alloys

Corrosion rates are classified into three grades: A (<25 mdd), B (<250 mdd), and C (<500 mdd). For WC-Co alloys, only low binder content alloys exhibit comprehensive corrosion resistance. In contrast, WC-Ni·Mo·Co·Cr alloys maintain considerable corrosion resistance even with 10% binder content. Notably, WC-2% Ni·Mo·Co·Cr alloys demonstrate excellent resistance under all tested conditions.

WC-Ni·Mo·Co·Cr alloys are widely used in manufacturing ballpoint pen tips. These alloys outperform traditional WC-Co·Ni·Cr alloys in various properties, are easier to produce, and have lower production costs, making them ideal materials for corrosion-resistant ballpoint pen tips.

Conclusions

1.The corrosion resistance of WC-based cemented carbides is primarily determined by the resistance of the binder phase. Lower binder content results in better condition. Alloys with Ni·Mo·Co·Cr as the binder exhibit significantly lower corrosion rates than WC-Co alloys, especially those with low binder content.

2.The corrosion rate of WC-based cemented carbides is related to the grain size of the hard phase. Finer grains lead to poorer corrosion resistance.

3.Small amounts of heterogeneous carbides, such as Cr?C? and Mo?C, can improve the resistance of WC-Co alloys, while TaC has little to no effect.

4.Graphite reduces the resistance of WC-based alloys, whereas the η1 phase significantly enhances it. Therefore, the ideal corrosion-resistant alloy should have carbon content controlled at the lower limit of the two-phase region or allow the formation of dispersed η1 phase without excessively compromising mechanical properties.

5.Low binder content alloys with good corrosion resistance can be prepared using chemical mixing to produce composite powders, intensified ball milling, and activated sintering processes, achieving high physical and mechanical properties.

6.The study of the corrosion resistance of WC-based cemented carbides provides a basis for their broader application.