Microstructure and tribological performance of Cr7C3-(Ni,Cr)3(AI,Cr) coating deposited from Cr7C3 in-situ synthesized alloy powder

Paper in proceeding, 2016

The work is aimed at developing a new type of Cr7C3-(Ni,Cr)3(AI,Cr) coatings for parts used in heavy-duty diesel engine. The feedstock, in which the stripe shaped Cr7C3 was in-situ synthesized, was firstly prepared by vacuum melting and gas atomization, then it was subjected to high velocity oxy-fuel(HVOF) spraying to deposited coating.The element composition, microstructures and the phase composition of the powder, as well as the sprayed coating were analyzed by chemical analysis, SEM and XRD. The hardness and sliding wear performance of the sprayed coating was also tested and compared to a commercial Cr3C2-NiCr coating used on piston ring.The results showed that the content of carbon in feedstock was almost the same as it was designed, and the volume content of Cr7C3 was increased with the more carbon and chromium added. The phases of the sprayed coating was also mainly the Cr7C3 and the Cr doped Ni3AI, and the ratio of them was almost similar to it in the powder. With the increased content of Cr7C3 in coating, the microhardness at room temprature was firstly increased to about 1000Hv0.3, but then minor decreased. When the temprature rised to 700°C, the microhardness of the coating was almost no changed, which showed its potential application at the high temprature.The coating involved 70vol.% and 77 vol.%Cr7C3 was showed the improved wear resisrance, lower friction coefficient and better compatibility to contourpartthan other Cr7C3-(Ni,Cr)3(AI,Cr) coatings and Cr3C2-NiCr coating.