High Temperature Oxidation Protection of Refractory Metal Alloys for Hypersonic Vehicle Applications

Hypersonic flight requires materials capable of withstanding high temperatures, high heat fluxes, and high mechanical loading. Many hypersonic vehicle components, including control surfaces, engine components, and actively cooled leading edge structures, utilize high temperature niobium and molybdenum alloys such as C103 and TZM respectively. These refractory alloys have found use in hypersonic vehicle applications because of their shared properties, including high melting point and excellent high temperature strength. To date, conventional oxidation-protective coatings such as R512E have provided sufficient oxidation protection to the metal alloys. However, as hypersonic vehicle performance advances, these metallic components will be exposed to operating environments that far exceed the capabilities of conventional oxidation protection coatings. To enable the next generation of metallic components for hypersonic vehicle applications, new oxidation-protective coating systems will be required to protect the alloys from oxidation at high temperatures. To extend the operating temperature range of carbon/carbon (C/C) composites for hypersonic applications that experience the highest heat fluxes, Ultramet has developed and successfully demonstrated a hafnium carbide-silicon carbide (HfC-SiC) coating, designated Ultra2000 and applied via chemical vapor deposition (CVD), as a replacement for SiC on C/C structures through extensive prior and currently ongoing work. The objective of the proposed project is to develop a coating system that enables Ultra2000 to be applied to C103 and TZM alloy substrates. The goal is to develop a coating system that results in a strongly bonded Ultra2000 topcoat on C103 and TZM that is resistant to thermal shock and provides high temperature oxidation protection for these alloys. A fully developed and characterized coating material system and process for Ultra2000 on C103 and TZM will be developed. Each element of the process will be fully characterized and optimized to ensure that the best-performing coating system is identified. The effort will culminate with a demonstration of the optimized coating system for C103 and TZM in a representative hypersonic environment, which will provide the opportunity to assess the coating systemÆs thermal shock and high temperature oxidation protection capabilities. The process development and material characterization performed in this project will provide a fundamental understanding of these coatings on the metallic alloy substrates and will support faster progression of the coating systemÆs TRL toward program insertion.