Microstructure and oxidation behaviour of MoSi2 coating combined MoB diffusion barrier layer on Mo substrate at 1300 °C

Abstract

To improve the oxidation resistance of a Mo substrate at high temperatures, MoSi2–MoB double layers were prepared on the surface of the substrate using a two-step pack cementation method. The isothermal oxidation tests indicate that the weight loss of MoSi2–MoB double layers was only 6.3824 mg/cm2 after oxidation at 1300 °C for 15 h, whereas the untreated Mo experienced serious weight loss and the weight loss was 606.775 mg/cm2 after only 90 min. Following oxidation exposure, the oxidized coating became six complex layers due to correlation diffusion among Mo, Si and B. The double layers showed excellent high-temperature oxidation resistance due to the formation of a dense and continuous SiO2 layer with low O2 permeability. Meanwhile, in situ fabrication of a novel Mo5SiB2 layer could prevent inward diffusion of Si.