Innovative Approaches to Develop Foreign-Object-Damage (FOD) Tolerant Coatings for Ceramic Matrix Composites (CMCs)

CMCs are currently being considered and used for aeroengine airfoil applications with a goal of increased specific power. Of a particular concern of CMCs regarding of life-limiting degradations is impact damage by small foreign objects. Fracture toughness and hardness have been the dominant material properties for determining the foreign objective damage (FOD). A material with both high hardness and high fracture toughness would be expected to have better FOD tolerance. Ceramics are promising for impact resistant coating (IRC) to alleviate the FOD due to their high hardness and high fracture strength. However, their fracture toughnesses are not sufficiently high to fully utilize such useful properties. Such problems can be solved by applying the UES composite coating technology. The composite coatings are remarkably tough, strong, hard, and readily coated, and that seems to meet the needed material properties. The goal of the Phase I program will be both demonstration of technical feasibility and development of tough, strong, and hard coating on commercial SiCf-SiC composites, in order for alleviating the FOD. Subsequently, muti-functional all-in-one coating system that can realize both FOD tolerance and oxidation resistance, will be developed during the Phase II program.