Dissociative adsorption of in-situ grown NiBi with oxygen enabling lower friction and wear of nickel-based composite coating at elevated temperature

Ni-based alloy coatings are increasingly being used in many high-temperature mechanical systems, although they may not necessarily achieve good friction and wear. This study introduces an innovative approach for delivering self-lubricating capability to Ni-based coatings by combining atmospheric plasma spraying (APS) and hot isostatic pressing (HIP). We demonstrate that HIP improves the densification, hardness, and adhesive strength of the coatings while offering outstanding friction reduction and wear resistance at 400 °C. This superior performance is attributed to the dissociative adsorption of in-situ NiBi compounds with oxygen, which results in the formation of BiNiO3 and NiO during friction. These compounds are key to the mitigation of interfacial adhesion and the formation of low-shear oxide tribolayers. This study provides a new method for preparing low-friction and anti-wear Ni-based coatings and outlines the chemical design rules for their self-lubricating properties through surface microstructural characterizations and atomic calculations.