Abstract: Achieving complete densification of ultrafine-grained tungsten carbide (WC) without inducing grain growth has long been a challenge limiting its industrial applications. The dynamic sinter forging process, which involves forging of incompletely dense materials under oscillatory pressure, facilitates densification while suppressing grain growth. This study explores the effects of oscillatory pressure amplitude during dynamic sinter forging on the microstructure and tribological properties of WC. The results show that increasing pressure amplitude leads to higher relative density of WC, combined with the reduction in grain size, an increase in the proportion of low-angle grain boundaries and special Σ2 boundaries, as well as an enhancement of dislocation density (~10¹⁵/m²). 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/m², respectively. With increasing pressure amplitude, both of the friction coefficient and the wear rate gradually decrease, with adhesive wear and ploughing identified as the dominant wear mechanisms. The reduction in wear rate is attributed to complete densification, finer grains, and higher dislocation density resulting from the increased pressure amplitude. Grain refinement and high dislocation density enhance plastic deformation capacity and hardening ability during wear, thereby increasing hardness of worn surface while mitigating crack initiation and propagation. Furthermore, special Σ2 boundaries also effectively impede dislocation motion, thereby improving strain hardening capability and contributing to the enhanced hardness of worn surface.

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