| Niobium alloys are candidate thermostructural materials in hypersonic flight applications because of excellent mechanical properties at elevated temperature; however, their susceptibility to oxidation requires the use of coatings. Multiphase silicide coatings containing iron, chromium, niobium, and silicon have historically been successful in protecting niobium in oxidizing environments, although little scientific understanding of this coating system is provided in publically available literature. Research efforts in process development, microstructural characterization, oxidation testing, and thermodynamic modeling have led to clarification of the coating microstructure, microstructural evolution, and the performance of the coating in oxidizing environments. These research efforts have led to strategies for improving coating performance, including surface planarization and modifying the coating with a dispersion of submicron alumina particles. |
