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

Abstract

MoSi2 coatings are prepared using spent and commercial MoSi2 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 MoSi2 coating using commercial MoSi2 (MC coating) after SPS while MoSi2 coating using spent MoSi2 (MS coating) is dense with low porosity. (Mo,Nb)5Si3 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 Mo5Si3 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 SiO2 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.