High-Temperature Cyclic Oxidation Behavior of Ti3SiC2/MoSi2 Composite Coatings on Nb–Si-Based Alloys

The long-term cyclic oxidation behavior of a single MoSi₂ coating, 10%, and 50% Ti₃SiC₂/MoSi₂ composite coatings on Nb–Si-based alloys is systematically investigated. The thermal gravimetric analysis reveal that the single MoSi₂ coating initially exhibits a stable mass change (–3.7 mg cm⁻²) for ≈37 cycles, followed by a rapid increase in mass gain (2.2 mg cm⁻² after 100 cycles). The 50% Ti₃SiC₂/MoSi₂ composite coating demonstrated linear oxidation kinetics with a mass gain of 3.5 mg cm⁻² after 100 cycles. Notably, the 10% Ti₃SiC₂/MoSi₂ composite coating showed superior stability, with minimal mass gain (–2.7 mg cm⁻²) over 100 cycles. The scale formed on the 10% coatings is characterized as compact, dense, and firmly adhered to the substrate, primarily consisting of an amorphous SiO₂ matrix interspersed with fine TiO₂ grains. After 100 cycles of cyclic oxidation, both the single MoSi₂ coating and the 50% composite coating exhibited significant degradation and damage at the edges.