Wide-temperature tribological properties and lubrication mechanisms of plasma-sprayed NiCrAlY-MoO3-Bi2O3 coatings in reciprocating sliding against superalloy

NiCrAlY-based composite coatings with 10–30 wt% MoO 3 -Bi 2 O 3 (1:1) were fabricated by atmospheric plasma spraying (APS) for high-temperature self-lubrication. Their tribological behaviors against GH5188 superalloy were evaluated from room temperature (RT) to 800 ℃. While both porosity and microhardness increased with oxide content, the 20 wt% coating (NMB2) exhibited optimal overall performance, achieving a minimum friction coefficient of 0.28 and a wear rate of 2.84 × 10 −5 mm 3 /(N·m) at 800 ℃. At elevated temperatures, lubricating oxides such as NiMoO 4 and CoMoO 4 formed on the wear surface. Concurrently, Co and W from the GH5188 counterpart oxidized and transferred, contributing to a stable composite tribofilm. This synergistic film effectively reduced friction and wear, identifying the NMB2 as a promising protective solution for high-temperature reciprocating components in aerospace applications.