Element diffusion behaviors at high temperature and their effects on microstructure and tribological properties of Cr2O3 films

Abstract

Chromic oxide (Cr2O3) films were deposited on iron-based and nickel-based superalloys via arc ion plating and annealed. The findings indicate that only a small amount of Fe and Mn is diffused into the as-annealed Cr2O3 film deposited on the iron-based alloy, and the spinel structure of octahedral MnCr2O4 is formed along with the diffusion of Mn element onto the film surface, contributing to further suppression of the high temperature oxidation of the elements in the film. In contrast, Ti, Nb, Al and Mn elements from the nickel-based alloy undergo obvious segregation and oxidation at the grain boundaries during annealing at elevated temperatures, accompanying the formation of a continuous mesh-like bulge structure on the film surface. As a result, the as-annealed Cr2O3 film on the iron-based superalloy exhibited a relatively high friction coefficient and wear rate during sliding against the alumina ball. The as-annealed Cr2O3 film on the nickel-based alloy has a low friction coefficient and a low wear rate from room temperature to 800 °C, because its surface mesh-like bulge structure can effectively reduce the contact area of the sliding pair and keep off its rubbed surfaces.