Cemented carbides are widely used in demanding engineering applications where corrosion resistance is crucial for long-term performance. While extensive research has focused on conventional hard alloys, the corrosion behavior of materials with controlled matrix granule-to-network structure ratios remains poorly understood. This structural parameter significantly influences both mechanical properties and chemical stability, yet systematic studies comparing different configurations are notably absent from the literature.

Fig.1?FSEM morphology of matrix and granular cemented carbide

Comparative Investigation of Corrosion Mechanisms in Hard Alloys with Engineered Matrix Granule-to-Network Architectures

This study systematically examines how controlled variations in the granule-to-network ratio (20:80 to 80:20) influence the electrochemical degradation behavior of WC-Co cemented carbides. Using a combination of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and advanced microstructural characterization, we establish quantitative correlations between three-dimensional phase connectivity and key corrosion parameters, including charge transfer resistance, corrosion current density (i_corr), and passive film stability. The research particularly focuses on elucidating how network continuity versus granular isolation affects: (1) anodic dissolution kinetics of the cobalt binder phase, (2) galvanic coupling effects between WC grains and metallic binder, and (3) penetration pathways for corrosive species in marine-grade NaCl environments. Our findings provide a microstructure design roadmap for developing next-generation hard alloys with optimized corrosion-wear synergy for extreme service conditions in offshore, mining, and chemical processing applications.

Corrosion Resistance: A Critical Factor in Cemented Carbide Applications

Cemented carbides are widely used in engineering practice, and their corrosion resistance has always been a critical factor affecting engineering reliability. In industrial applications, cemented carbides are susceptible to oxidation, chemical corrosion, and erosion. After exposure to corrosion, the alloy exhibits various degradation phenomena during service, leading to a sharp deterioration in surface properties and wear resistance, thereby shortening the operational lifespan of engineering components. Therefore, enhancing both physical properties and corrosion resistance is crucial for materials intended for complex working environments.

Fig.2?Mechanical properties of cellular cemented carbides with?different matrix granule ratios

(a)XW5；(b) XW6；(c) XW7；(d) XW8

Fig.3 SEM morphology of cellular cemented carbides with different matrix granule ratios

Grain Size Effects on Electrochemical Corrosion Behavior

ZHANG L et al. investigated the electrochemical corrosion behavior of WC-10Co cemented carbides with different WC grain sizes. Their results demonstrated a strong linear correlation between charge transfer resistance, corrosion current density, and WC grain in the solution. Similarly, KELLNER F J J et al. studied the corrosion behavior of cemented carbides with varying grain sizes using electrochemical methods. Their experimental findings revealed that smaller grain sizes enhance corrosion resistance, and the corrosion behavior is significantly influenced by the dissolved W and C content in the Co binder phase.

Fig.4 Potential polarization curve of cellular cemented carbides with different matrix granule ratios

Research Gap: Network-Structured Alloys in Corrosive Environments

While the corrosion behavior of conventional cemented carbides has been extensively studied, there is limited comprehensive research on network-structured alloys in corrosive environments. In this study, YG10-grade alloy was selected as the matrix material, and YG8-grade alloy as the granular material to fabricate network-structured alloys. The research focuses on examining the influence of matrix-to-granule volume ratio on the microstructure and corrosion performance of the network-structured alloy.

Fig.5 Nyquist curve of cellular cemented carbides with different matrix granule ratios

Fig.6 Bode curve of cellular cemented carbides with different matrix granule ratios

Fig.7 Equivalent circuit diagram used to fit EIS

(a)XW5；(b) XW6；(c) XW7；(d) XW

Fig.8 Corrosion topography of cellular cemented carbides with different matrix granule ratios

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Вывод

This study investigated the effects of the matrix-to-granule ratio on the microstructure and corrosion resistance of network-structured alloys in a 3.5% NaCl solution. The key findings are as follows:

1.Mechanical Properties

As the granule proportion increased, the Vickers hardness of the alloy first increased and then decreased, while the flexural strength gradually improved.

The optimal comprehensive mechanical properties were achieved at a matrix-to-granule ratio of 30:70.

2.Polarization Curve Analysis

Both the corrosion potential and corrosion current density initially decreased and then increased with higher granule proportions.

Increasing the granule ratio reduced both the corrosion tendency and corrosion rate of the network-structured alloy.

3.Electrochemical Impedance Spectroscopy (EIS) Results

A higher granule proportion enhanced the electrochemical impedance of the alloy.

At a matrix-to-granule ratio of 30:70, the fitted charge transfer resistance (R_t = 1,860 Ω·cm2) and constant phase element exponent (n = 0.8878) reached their maximum values, indicating minimal surface corrosion and the fewest corrosion pits.