Cyclic oxidation behavior of Fe-Cr modified slurry silicide coated Nb-18.7Si alloyed with Ti and Zr

Abstract The Nbss/Nb 3 Si-Nb 5 Si 3 alloys exhibit good high-temperature strength and creep resistance, and are candidate high-temperature materials for hypersonic aerospace applications. However, their poor oxidation resistance necessitates the application of protective coatings.The present study examines the comparative cyclic oxidation behavior of uncoated and Fe-Cr modified slurry silicide coated Nb-18.7Si, Nb-18.7Si-5Ti and Nb-18.7Si-5Zr (in at.%) alloys in air at temperatures between 800–1400 °C. The uncoated samples showed extensive loose-scale formation from the initial stages of oxidation. On the other hand, the protective multi-phase oxide scale formed on the coating surface prevented dimensional degradation for at least 5–7 h at high temperatures of 1400 °C.