Fatigue Behaviour of HVOF-Sprayed WC–Co–VC and Cr 3 C 2 –NiCr–VC Coatings on AISI 4340 Steel

The study centres on the implications of WC–Co–VC and Cr 3 C 2 –NiCr–VC coatings made on AISI 4340 steel substrate with respect to fatigue, before and after shot peening. Fatigue tests in the axial direction were performed to obtain a plot of stress and cycles to failure (S–N curve), for both the base material and the coated samples, before and after shot peening and were subjected to plastic deformation. The results reveal that the coated samples after shot peening have shown increased fatigue strength property, compared to coatings before shot peening. Also, the coated samples have exhibited comparable fatigue properties over the base material AISI 4340 steel. The trends obtained clearly enumerates the fact that peening enhances the fatigue limit of the coated samples. The other supporting tests, viz. microhardness, surface roughness and microstructures have given able support to the fatigue findings. Between the coatings evaluated for fatigue strength, Cr 3 C 2 –NiCr–VC coating has been proved to possess best fatigue properties. Further, these coated samples were subjected to shot peening, and the fatigue limits have improved compared to unpeened coated samples. The shot peening increases the fatigue limit of Cr 3 C 2 –NiCr–VC and WC–Co–VC coatings by 48.36% and 38.19%, respectively.