Preparation and oxidation behavior of MoSi2–CrSi2–Si3N4 composite coating on Mo substrate

• A MoSi2–CrSi2–Si3N4 composite coating on Mo Substrate was prepared by in situ diffusion.
• Phase changes and microstructure of the MoSi2–CrSi2–Si3N4 coating were studied.
• Oxidation behavior of MoSi2–CrSi2–Si3N4 coating at 1600 °C in air is investigated.
• MoSi2–CrSi2–Si3N4 coating shows excellent high temperature oxidation resistance.
• Effect of Cr element in MoSi2–CrSi2–Si3N4 coating is analyzed.

MoSi2–CrSi2–Si3N4 composite coating on Mo substrate was made by in situ diffusion of Mo chromising and by ammonia nitriding and siliconizing. The oxidation behavior of MoSi2–CrSi2–Si3N4 and MoSi2–Si3N4 coatings at 1600 °C in air was investigated in detail. Phase constitution and microstructure of the coatings were analyzed by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Although mainly enriched on the surface, the Cr element in the MoSi2–CrSi2–Si3N4 coating inhibits the diffusion of Si and the formation of volatilizable MoO3 phase during oxidation. Thus MoSi2–CrSi2–Si3N4 coating exhibits better oxidation resistance than MoSi2–Si3N4 coating.