HfC–HfO 2 modified high/superhigh temperature thermal protection coating for superior hot corrosion resistance and antioxidation performance

With the advances in thrust-weight ratio, the service temperature of gas turbine engines even exceeds 1500℃, which is urgent to develop high/superhigh temperature thermal protection systems for long-term service. Niobium alloys are increasingly viewed as a promising structural material for high-temperature applications due to their superior high-temperature mechanical strength, but the “pest” catastrophic oxidation greatly restricts its further application. Herein, a HfC-HfO2 modified silicide coating was prepared via an innovative method of halide-activated pack cementation combined with liquid-plasma-assisted particle deposition and sintering on niobium alloys, endowing the 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, exhibiting a significant improvement in high-temperature performance compared with the single NbSi2 coating. The corroded gain of composite coating is only 13.94 mg·cm-2 after the corrosion time of 200 h at 900℃, and shows an intact oxide scale surface after oxidation at 1500℃ for 500 min. This improvement is ascribed to the formed robust Hf-rich skeleton provided by the deposited HfC-HfO2 layer, which can accelerate the formation of the high stability corroded layer/oxide scale. Besides, multiple stress release mechanisms of the composite coating at high temperatures also provide huge contributions for long-term service. All these merits render the HfC-HfO2 modified composite coating on niobium alloys competitive for the development of high/superhigh temperature thermal protection systems for long-term service.