Wear behavior of nitrocarburized JIS SKD61 tool steel

The surface wear characteristics of the nitrocarburized JIS SKD61 tool steel were investigated. The ferritic substrate (FS) JIS SKD61 tool steel as received was pretreated in quenching and tempering processes to obtain the tempered martensitic microstructure. Specimens were then nitrocarburized for 1, 3, and 5 h. The chemistry, microstructure, and hardness of the nitrocarburized coatings were analyzed. Wear behavior was examined on a block-on-roller wear tester under unlubricated conditions. The results have shown that white layers were predominantly composed of the ϵ-phase iron nitrides dispersed with γ′-phase, and a large amount of nitrogen and carbon trapped in the ferrite phase was observed in the diffusion layer for FS. The nitrocarburizing treatment increased the surface roughness, hardness and the friction coefficients of the specimens. Wear contact pressures and nitrocarburized holding time also affected the friction coefficients of the nitrocarburized specimens. In this study, both the FS and the tempered martensitic substrate (TMS) specimens treated with subsequent nitrocarburizing process have shown significant improvement of the wear resistance. Wear behaviors of the specimens nitrocarburized for 1, 3, and 5 h did not vary significantly.