Innovative Concepts for Lightweight, Low-Cost, High Temperature Turbine Components

Carbide composites of carbon and Group IV metals (Ti, Zr, Hf) will be developed for high temperature turbine components. Material will be fabricated from a metal and graphite fragment feedstock through a single step melt-casting process, providing near net shape components. Carbon content will be a controlled variable, taking advantage of the solubility of carbon in molten Group IV carbides. Hypereutectic carbides, upon solidification, precipitate highly oriented graphite flakes within the eutectic structure. These flakes provide advantages in thermal and mechanical properties with significantly reduced density. For titanium-carbon (TiC-C), it is useful to a temperature >2000 °C, the density reduced from 4.93 g/cc in the stoichiometric to about 4.0 g/cc which reduces mass relative to super alloys. In an elevated temperature oxidizing environment, a stable metal oxide coating forms in situ on Group IV carbides that inhibits degradation and contributes to excellent dimensional stability. Compared to other processes for CMC fabrication, single step casting to a near net component is expected to reduce both cost and fabrication time. The effort will emphasize the fabrication of TiC-C samples and measurement of properties critical for systems use. Phase 2 will provide full size TiC-C turbine components for evaluation by System Contractors.