HfC–HfO₂ modified high/superhigh temperature thermal protection coating for superior hot corrosion resistance and antioxidation performance

With advances in the thrust-weight ratio, the service temperature of gas turbine engines even exceeds 1500 °C, which is urgent for the development of high/superhigh-temperature thermal protection systems (TPSs) for long-term service. Niobium alloys are increasingly viewed as promising structural materials for high-temperature applications because of their superior high-temperature mechanical strength, but the “pest” catastrophic oxidation greatly restricts their further application. In this study, a HfC–HfO₂-modified silicide coating was prepared via an innovative method of halide-activated pack cementation (HAPC) combined with liquid-plasma-assisted particle deposition and sintering of niobium alloys, resulting in a composite coating with excellent hot corrosion resistance and high-temperature oxidation resistance. This modified multilayer coating is characterized by the synergistic combination of a dense NbSi₂ inner layer and a HfC–HfO₂ porous outer layer, resulting in a significant improvement in high-temperature performance compared with that of the single NbSi₂ coating. The corrosion gain of the composite coating is only 13.94 mg·cm⁻² after a corrosion time of 200 h at 900 °C, and an intact oxide scale surface is observed after oxidation at 1500 °C for 500 min. This improvement is attributed to the formation of a robust Hf-rich skeleton provided by the deposited HfC–HfO₂ layer, which can accelerate the formation of a highly stable corroded layer/oxide scale. In addition, multiple stress release mechanisms of the composite coating at high temperatures also provide substantial contributions to long-term service. All these merits make HfC–HfO₂-modified composite coatings on niobium alloys competitive for the development of high/superhigh-temperature thermal protection systems for long-term service.