Effect of Oscillatory Pressure Amplitude on Microstructures and Wear Resistance of Tungsten Carbide

doi:10.15541/jim20250051

Abstract

Abstract:

Achieving complete densification of ultrafine-grained tungsten carbide (WC) without inducing grain growth has long been a challenge, which limits industrial applications of WC. The dynamic sinter forging process, which involves forging of incompletely dense materials under oscillatory pressure, facilitates densification while suppressing grain growth. This study explores effects of oscillatory pressure amplitude during dynamic sinter forging on microstructure and tribological properties of WC. The results show that increasing pressure amplitude leads to higher relative density of WC, accompanied by a reduction in grain size, an increase in proportion of low angle grain boundaries and special grain boundaries Σ2, as well as an enhancement of dislocation density. At a pressure amplitude of 20 MPa, the relative density, average grain size and dislocation density of WC reach 99.6%, 203 nm and 1.68×10¹⁵ m^-2, respectively. With an increase in pressure amplitude, both the friction coefficient and the wear rate gradually decrease. Under this condition, the adhesive wear and ploughing were identified as the dominant wear mechanisms. The reduction in wear rate is attributed to complete densification, finer grains and higher dislocation density, which result from the increased pressure amplitude. Grain refinement and high dislocation density enhance plastic deformation capacity and hardening ability during the wear, thereby increasing hardness of worn surface while mitigating crack initiation and propagation. Furthermore, special grain boundaries Σ2 also effectively impede motion of dislocation, thereby improving strain hardening capability and enhancing hardness of worn surface.

Key words: tungsten carbide, oscillatory pressure, microstructure, wear behavior

CLC Number:

TB321

ZHONG Weimin, ZHAO Ke, WANG Kewei, LIU Dianguang, LIU Jinling, AN Linan. Effect of Oscillatory Pressure Amplitude on Microstructures and Wear Resistance of Tungsten Carbide[J]. Journal of Inorganic Materials, 2025, 40(9): 964-970.

Figures/Tables 12

Fig. 1 Schematic of dynamic sinter forging

Fig. 2 Processing parameters of WC fabricated by dynamic sinter forging

Fig. 3 XRD patterns of WC samples prepared under different pressure amplitudes

Fig. 4 Relative densities and fracture morphologies of WC samples prepared under different pressure amplitudes (a) Histogram of relative density against pressure for WC samples; (b-d) Fracture morphologies of WC samples prepared under (b) 80, (c) (70±10), and (d) (60±20) MPa

Fig. 5 Diagrams of grain orientations (up) and grain size distributions (down) for WC samples prepared under different pressure amplitudes (a) 80 MPa; (b) (70±10) MPa; (c) (60±20) MPa. Colorful figures are available on website

Fig. 6 (a-c) Statistical diagrams of grain misorientation angle and (d) variation in fraction of low angle grain boundary (LAGB) and Σ2 grain boundary for WC samples prepared under different pressure amplitudes

Fig. 7 (a-c) KAM maps, (d) dislocation densities, and (e) statistical diagrams of KAM angle for WC samples prepared under different pressure amplitudes (a) 80 MPa; (b) (70±10) MPa; (c) (60±20) MPa. HAGB: high angle grain boundary. Colorful figures are available on website

Fig. 8 Tribological properties of WC samples prepared under different pressure amplitudes (a) Friction coefficient as a function of time; (b) Average friction coefficient and wear rate vs. pressure; (c) Wear scar depth vs. width

Fig. 9 Wear scar morphologies of WC samples prepared under different pressure amplitudes (a-c) 80 MPa; (d-f) (70±10) MPa; (g-i) (60±20) MPa

Fig. 10 Morphology and element characterization of adhesive phase of WC sample prepared under pressure amplitude of 10 MPa (a) SEM image; (b-e) EDS mappings corresponding to (a); (f) EDS spectrum corresponding to point in (a) marked with + symbol

Fig. S1 SEM images of different locations on cross-section of WC sample prepared under pressure amplitude of 20 MPa

Fig. S2 Three-dimensional surface topographies of WC samples prepared under different pressure amplitudes (a) 80 MPa; (b) (70±10) MPa; (c) (60±20) MPa

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