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

Spent MoSi 2 heating elements, which worked in the industrial electrical furnace at high temperature, were crushed into powders and reused as coating raw materials. ZrO 2 was added into spent MoSi 2 powders to fabricate MoSi 2 -ZrO 2 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 MoSi 2 coating while ZrO 2 -containing coatings are crack-free with the formation of (Mo,Nb) 5 Si 3 diffusion layer after SPS, indicating good metallurgical bonding. After oxidation at 1500 °C for 20 h, the lowest mass gain is obtained by MoSi 2 -30ZrO 2 coating. SiO 2 and ZrSiO 4 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 MoSi 2 -30ZrO 2 coating is dense without any voids or cracks, demonstrating better high-temperature oxidation resistance than that of single MoSi 2 coating.