Influence of Alumina Particles on Tribology of Autocatalytic Ni-P Coatings at High Temperature

Abstract

The present work considers the effects of incorporation of hard Al2O3 particles on the structure, microhardness, and tribological behavior of electroless Ni-P coatings at room temperature and elevated temperature. Ni-P (9% P) coating shows a typical amorphous structure that changes to a mixture of nanocrystalline and amorphous structure due to the addition of alumina particles. The incorporation of Al2O3 particles is found to enhance the overall hardness and wear resistance of the Ni-P coating. Exposure to high temperature during tribological tests acts as brief heat treatment, initiating microstructural changes in the coating which further increases the hardness of the deposit. The scanning electron micrograph of the worn surface of the coating reveals both abrasive and adhesive wear phenomena governing the wear mechanism at elevated temperature. The development of the oxide layer is another important characteristic of the coatings examined under high temperatures (around 500°C).