Dual-strategy regulation of thermal protection coating resistant to high-temperature ablation above 2000 °C

Niobium alloys are promising for the thermal structural components in advanced aerospace vehicles, but suffer from insufficient temperature carrying capacity and limited anti-oxidation/ablation performance at extremely high temperatures. Herein, a Nb 2 O 5 -SiO 2 /HfC-HfO 2 composite coating is presented for superior ablation resistance above 2000 °C by co-regulation of the infrared radiation and robust oxide scale. This composite coating has a high emissivity of 0.91 across a wide range of 3-20 μm, due to the strong lattice vibration absorption matching and the rough surface. After plasma ablation for 60s (peak temperature >2500 °C), the composite coating shows significantly enhanced anti-ablation performance compared with NbSi 2 coating, despite a small amount of delamination and peeling occurring in the oxide scale during the ablation cooling process. The high performance resulted from the formation of a stable Hf-Nb-Si-O oxide scale, with the characteristic of a crystallization phase at the micrometer scale and an amorphous feature at the nanometer scale. Moreover, the increased viscosity of the glassy silica layer is achieved with the addition of HfC, forming a compact oxygen barrier layer with comparatively reduced oxygen permeability, as well as the new products of HfSiO 4 with a negative volume expansion rate. The proposed coating greatly extends the service temperature of metal matrix, providing valuable insights for the thermal protection design of advanced aerospace vehicles.