Enhanced hot corrosion resistance and thermal radiation property of NbSi₂/Nb₂O₅-SiO₂/SiC ceramic coating for niobium alloys thermal protective system

A NbSi2/Nb2O5-SiO2/SiC multilayer coating was developed on niobium alloys to improve the hot anti -corrosion and infrared thermal radiation performance simultaneously. This novel modified silicide coating includes a NbSi2 inner layer, a Nb2O5-SiO2 pre -oxidation intermediate layer, and a SiC particle deposition and sintering outer layer, showing a strong multilayer synergistic. This multilayer design strategy endows the coating a high emissivity above 0.9 at 700 degrees C across the entire range of wavelength (3-20 mu m), significantly enhancing the infrared thermal radiation performance than that of the NbSi2 coating and PEO-coating. Accordingly, the enhanced infrared radiation performance is ascribed to the synergistic effects of vibrational absorption between the Nb2O5, SiO2 and SiC phase in the ceramic outer layer over multiple bands, as well as the porous surface structure of LPDS-coating; Meanwhile, the as -prepared LPDS-coated specimen exhibits an excellent anticorrosion performance with a mass gain of -0.56 mg/cm2 under the hot corroded environment for 100 h. The improved hot anti -corrosion performance is main the result of a synergistic effect between a dense preoxidation layer and a continuous SiO2 film layer with self-sealing, as well as the SiC providing an extra Si source substantially.