Long term protection of silicide coating at 1700 °C in air with HfO₂ modification

HfO₂-modified MoSi₂ coating was fabricated on Nb-alloy via supersonic atmosphere plasma spraying to protect against ultra-high temperature oxidation. The service life of the modified coating reached 200 h at 1700 °C, and the excellent oxidation resistance was attributed to the SiO₂+HfSiO₄ duplex scale stabilized by the Hf-dopant and the pinned phase of HfSiO₄. Continuous volatilization of SiO₂ triggered the outward diffusion and significant loss of Si element, dominating the degradation of the MoSi₂-based coating during oxidation. This work achieved long-term protection for Nb-alloy at 1700 °C, providing effective method and theoretical foundations for the design of the antioxidant coating.