Fabrication of Si-Cr-V coatings for high-temperature oxidation resistance protection of TaW/NbW refractory alloys

As critical structural materials for rocket engines, TaW/NbW refractory alloys face severe oxidation issues under high-temperature service conditions, making the development of effective surface protection technologies imperative. This study successfully fabricated Si-Cr-V oxidation-resistant coatings on TaW (Ta12W, Ta10W) and NbW (Nb521, Nb6621) alloys using a slurry sintering method, systematically evaluating the coatings’ static oxidation resistance at 1600°C and 1800°C, along with their thermal shock resistance under air cooling (800 ~ 1800°C) and water quenching (room temperature ~ 1800°C) conditions. The experimental results show that at 1800°C, the effective protection times of the coatings on Ta12W, Ta10W, Nb521, and Nb6621 alloys reached 540, 360, 590, and 535 minutes respectively, while at 1600°C, the protection times for coatings on both Nb521 and Nb6621 alloys extended to 840 minutes. Particularly noteworthy is that the coating on Nb521 alloy withstood 190 thermal cycles under air cooling (800 ~ 1800°C) and endured 341 cycles under water quenching (room temperature ~ 1800°C) without failure. Characterization using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) of the microstructural evolution and elemental distribution during high-temperature oxidation revealed the thermal protection mechanism of the Si-Cr-V coating: metal silicides in the coating undergo oxidative decomposition at high temperatures to form a dense SiO 2 ~ protective layer, which synergistically interacts with multiple metal oxides to establish a protective system, thereby effectively safeguarding the substrate alloy. This study provides an important technical solution for oxidation protection of high-temperature structural materials in aerospace applications, demonstrating significant practical value.