HfC–HfO <sub>2</sub> modified high/superhigh temperature thermal protection coating for superior hot corrosion resistance and antioxidation performance
Zhiyun Ye, Shuqi Wang, Shuang Yu, Xinrui Zhao, Yongchun Zou, Guoliang Chen, Lei Wen, Lina Zhao, Guangxi Zhang, Yaming Wang, Jia‐Hu Ouyang, Dechang Jia, Yu Zhou
Abstract
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-HfO<sub>2</sub> 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 NbSi<sub>2</sub> inner layer and a HfC-HfO<sub>2</sub> porous outer layer, exhibiting a significant improvement in high-temperature performance compared with the single NbSi<sub>2</sub> coating. The corroded gain of composite coating is only 13.94 mg·cm<sup>-2</sup> 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-HfO<sub>2</sub> 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-HfO<sub>2</sub> modified composite coating on niobium alloys competitive for the development of high/superhigh temperature thermal protection systems for long-term service.