Microstructure Characteristics and Oxidation Behavior of Molybdenum Disilicide Coatings Prepared by Vacuum Plasma Spraying

In this study, molybdenum disilicide (MoSi₂) coatings were fabricated by vacuum plasma spraying technology. Their morphology, composition, and microstructure characteristics were intensively investigated. The oxidation behavior of MoSi₂ coatings was also explored. The results show that the MoSi₂ coatings are compact with porosity less than 5%. Their microstructure exhibits typical lamellar character and is mainly composed of tetragonal and hexagonal MoSi₂ phases. A small amount of tetragonal Mo₅Si₃ phase is randomly distributed in the MoSi₂ matrix. A rapid weight gain is found between 300 and 800 °C. The MoSi₂ coatings exhibit excellent oxidation-resistant properties at temperatures between 1300 and 1500 °C, which results from the continuous dense glassy SiO₂ film formed on their surface. A thick layer composed of Mo₅Si₃ is found to be present under the SiO₂ film for the MoSi₂ coatings treated at 1700 °C, suggesting that the phenomenon of continuous oxidation took place.