Microstructure and oxidation resistance of a YSZ modified silicide coating for Ta-W alloy at 1800 degrees C

To develop an ultra-high temperature resistant coating for a reusable thermal protection system, a YSZ-modified Si-Mo coatings were prepared on Ta-10 W alloy by slurry reaction sintering method. The coating had a MoSi2-ZrSi2-SiO2 outer layer and a TaSi2-WSi2 inner layer. The coated sample remained intact after oxidation at 1800 degrees C for 10 h, while the untreated alloy was pulverized after 6 min. The coating withstood more than 200 shock heating cycles from room temperature to 1800 degrees C. Its outstanding oxidation resistance is attributed to its thermal matching with the alloy and formation of protective SiO2 scale containing high-melting ZrSiO4 and ZrO2.