Microstructure and high-temperature oxidation resistance of MoSi2-ZrO2 composite coatings for Niobium substrate

Spent MoSi2 heating elements, which worked in the industrial electrical furnace at high temperature, were crushed into powders and reused as coating raw materials. ZrO2 was added into spent MoSi2 powders to fabricate MoSi2-ZrO2 coatings on niobium by spark plasma sintering, and the microstructure and oxidation behavior of the coatings at 1500 and 1700 °C were explored. The results showed that cracks exist in MoSi2 coating while ZrO2-containing coatings are crack-free with the formation of (Mo,Nb)5Si3 diffusion layer after SPS, indicating good metallurgical bonding. After oxidation at 1500 °C for 20 h, the lowest mass gain is obtained by MoSi2-30ZrO2 coating. SiO2 and ZrSiO4 are formed on the composite coatings at elevated temperature, which improves the high-temperature oxidation resistance. After oxidation at 1700 °C for 60 min, the oxide scale of MoSi2-30ZrO2 coating is dense without any voids or cracks, demonstrating better high-temperature oxidation resistance than that of single MoSi2 coating.