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

Highlights: • The effect of Cr₂AlC MAX phase additions on the strengthening of Ni-Mo-Al alloy coated on piston ring is studied. • During the Air Plasma coating Cr₂AlC MAX phase decomposed into Cr₇C₃ and Al₂O₃ phases. • The in-situ formation of hard alumina and hexagonal (Cr₇C₃) phase toughens the matrix and improves the tribological properties and increases the coating life cycle. • 20 wt% Cr₂AlC blended Ni-Mo-Al alloy coating shows superior property in comparison to other coating and its properties are well matching with the industry needs. 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.