Microstructure and analysis of oxide scales formed on Cr–Si–Ni compacts in air and H2O-containing atmosphere

The purpose of this study was to characterize the oxide scales formed on various Cr–Si–Ni compacts at 1273 K in air and H2O-containing atmosphere by TEM. It was found that CrSi2–(5–20)mass%Ni compacts form double layer scales, consisting of an outer Cr2O3 layer and an inner SiO2 layer. The oxide scale changed from SiO2- to Cr2O3-based scale with an increase in the Ni concentration. However, it was observed that the oxide scale formed in H2O-containing atmospheres showed local SiO2 growth into the substrate. This result suggests that the inward oxidant diffusion promotes the local growth of SiO2 in the H2O-containing atmospheres.