Probing Indentation-Induced Inelastic Deformation Behavior of Functionally Graded WC-Co/SS Coating Via High Velocity Oxy-Fuel (HVOF) Process

Thermal sprayed WC-Co cermet coatings are well known for damage tolerant applications due to intrinsic high hardness. However, lack of metal-like toughness in these coatings causes a rather unpredictable coating failure involving delamination and spallation under contact loading and fatigue. Understanding crack propagation in such coatings gives insights to means of controlling crack paths, thus leads to the prevention of a catastrophic coating failure. In this study, functionally graded WC-12%Co / stainless steel coatings were sprayed via HVOF process to increase coating toughness and adhesion by minimizing thermal mismatch stress. The coatings were subjected to various indentation-induced strains to simulate the contact-loading scenario to the first approximation. The results suggest that the presence of a small compliant phase deflects a crack path without sacrificing overall coating strength.