Effect of Cr2AlC MAX phase addition on strengthening of Ni-Mo-Al alloy coating on piston ring: Tribological and twist-fatigue life assessment

The aim of the present study is to investigate the effect of Cr2AlC additions on the tribological properties of Piston Ring coated with Ni-Mo-Al alloy. For this Cr2AlC MAX phase was blended with Ni-Mo-Al alloy powder in different proportions (10 wt%, 20 wt% and 50 wt%) and coated on the stainless steel piston ring by Air Plasma Spraying (APS). During coating Cr2AlC MAX reacts with air and forms Cr7C3 and Al2O3 phases. The in-situ formation of Cr7C3 and Al2O3 was observed to strengthen the alloy. 20 wt% Cr2AlC additions to the Ni-Mo-Al alloy yields a good combination of properties, such as improved adhesion, hardness and wear resistance. Composite coating was found to be stable during the exfoliation test of the coated ring. Coating life cycles were found to be nearly doubled by MAX phase addition, as assessed through the twist-fatigue study. These improved properties could be attributed to the finely distributed oxides (alumina) and chromium carbides (Cr7C3) within the coated layer, which were formed in-situ during plasma spraying.