Enhanced wear resistance and fracture resistance of spherical WC reinforced nickel-based alloy coating by adding non-spherical WC

Abstract

Spherical WC particles are widely employed as hard phases to reinforce metal matrix coatings; however, their deposition during the surfacing process presents a significant challenge, resulting in limited improvements in coating hardness and wear resistance. In this work, these spherical WC as well as spherical/non-spherical WC particles have been used to prepare the WC reinforced nickel-based alloy coatings. The microstructure, mechanical, wear and fracture behavior of these coatings were investigated by detailed characterization. Results showed that spherical WC exhibited rapid sedimentation, and the primary decomposition products existed lump-like W₂C. The ultimate decomposition process was based on the exfoliation of the diffusion layer. The spherical WC/Ni coatings exhibited a hardness of 13 GPa and an elastic modulus of 253 GPa, respectively. Notably, the wear rate of these coatings was relatively high, measuring 7.038 × 10⁻⁶ mm³/(N·m), while the stress and strain were comparatively low, standing at only 272.5 MPa and 0.72 %. In contrast, spherical/non-spherical WC/Ni coatings demonstrated distinct differential sedimentation behavior. Spherical WC particles settled at the bottom of the coating, whereas non-spherical WC particles were dispersed in the middle and upper regions. The decomposition of non-spherical WC particles was governed by the dissolution and diffusion of W₂C, forming a skeleton-braided structure of M₇C₃, γ, and M₂₃C₆ phases on the coating surface. This unique structure increased the hardness of the coating to 21 GPa and the elastic modulus to 369 GPa, while reducing the wear rate to 2.853 × 10⁻⁶ mm³ (N · m) ⁻¹. In addition, the stress and strain reached 497.10 MPa and 1.97 % respectively, shifting the fracture mode to quasi-cleavage fracture with tear ridges. Overall, the spherical/non-spherical WC/Ni coating exhibited improved deformation resistance and superior wear resistance.