Effect of compressive stress on initial oxidation of nickel-based superalloy at high temperature

Abstract

The effect of compressive stress on the initial oxidation behavior of the Ni16Cr13Co4Mo superalloy in the air at 800 °C was investigated. Results show that oxidation of the alloy surface is promoted by compressive stress without altering the layered structure of the oxide film. The oxide film of unstressed specimen primarily consists of spinel-type oxide (Ni, Co)Cr₂O₄, whereas under compressive stress, corundum-type oxide Cr₂O₃ forms and the proportion increases with compressive stress. Mechanism analysis suggests that the stress level near the grain boundaries increased due to compressive stress, causing plastic strain at these sites, resulting in the formation of more dislocations and vacancies in the oxide film. This process promotes the outward diffusion of metal cations along the grain boundaries and the inward diffusion of oxygen. Thus, the oxide film consisting of Cr₂O₃ becomes thicker, which is beneficial to oxidation resistance.