Low-Cost Innovative Hi-Temp Fiber Coating Process for Advanced Ceramic Matrix Composites

MATECH GSM (MG) proposes 1) to demonstrate a low-cost innovative Hi-Temp Si-doped in-situ BN fiber coating process for advanced ceramic matrix composites in order to eliminate performance barriers that prevent practical use of advanced future NASA aircraft by performing interfacial coating on single fiber tows and fiber preforms that are applicable to the shape and structural requirements of advanced SiC/SiC super- and hyper-sonic components, and 2) to examine and model environmental durability of the fiber coating constituent in various hot-section CMC components.
The CVI coating process is costly and yields a porous non-uniform BN structure due to the low temperatures needed for diffusion and infiltration of the gaseous precursors. MG has discovered a faster, more economical and more versatile process for fiber interface coating formation, reactive-transformation-process (RTP), where the interface coating is formed from the ceramic fiber itself, a new innovative in-situ Si-doped BN-based fiber coating that is more stable during fabrication and service of Si-based CMC. The formation of an in-situ BN surface layer creates a more environmentally durable fiber surface not only because a more oxidation-resistant BN is formed, but also because this layer provides a physical barrier between contacting all single fibers with oxidation-prone SiC surface layers.