Microstructural Characterization and Anti-Oxidation Properties of Molybdenum Disilicide Coating on Niobium by Spent MoSi2-Based Materials

MoSi 2 coatings are prepared using spent and commercial MoSi 2 powders as raw materials to protect niobium (Nb) substrate by spark plasma sintering (SPS) technique, and the microstructure and oxidation resistance of the coatings at 1500 °C are investigated. Results showed that obvious pores are found in MoSi 2 coating using commercial MoSi 2 (MC coating) after SPS while MoSi 2 coating using spent MoSi 2 (MS coating) is dense with low porosity. (Mo,Nb) 5 Si 3 diffusion layer is generated between MS coating and the substrate with no gap or cracks, showing excellent metallurgical bonding. After long-term oxidation at elevated temperature, pores and exposed Mo 5 Si 3 can be observed in the oxide scale of MC coating, while dense and complete oxide scale is obtained by MS coating. Lowest mass gain (2.78 mg cm −2 ) is acquired by MS coating after oxidation at 1500 °C for 40 h because SiO 2 oxide scale is completely formed on the dense and bentonite-containing coating, blocking the diffusion of oxygen at high temperature. Compared with MC coating, no further oxidation occurs inside the MS coating or substrate, exhibiting better high-temperature oxidation resistance.