Microstructure, Wear Resistance, and Impact Fracture Behavior of In625-Ni/WC Gradient Coating Fabricated by Laser Cladding

In this study, the Inconel625-Ni60-Ni60/25%WC gradient coating (In625-Ni/WC GC) was prepared by adding a transition layer and changing the ratio of WC-reinforcing phase by the design method of laser cladding on Cr12MoV steel. The microstructure, wear resistance, and impact fracture behavior of GC were investigated. The results showed that the In625-Ni/WC GC had better internal metallurgical bonding properties without obvious defects. The surface phases of GC did not change significantly. The In625 layer was mainly composed of coarse columnar grains. The Ni/WC layer was mainly composed of fine dendritic and eutectic structures. The accumulation of heat from multi-layer deposition and limited diffusion at the interface between the In625 layer and Ni60 layer caused the upper Ni/WC layer to tend toward grain coarsening. The average friction coefficient and wear rate of In625-Ni/WC GC were 10.78% and 20.17% higher than those of the Ni/WC GC, respectively. The wear surface showed abrasive wear and slight adhesive wear. Notably, the impact toughness value of the DGC increased by 145.41%, and the fracture of the GC exhibited a composite fracture morphology in which cleavage fracture and ductile fracture coexisted. The fracture morphology of the In625 layer as the ‘softened region’ was dominated by dimples.