Fabrication of Ceramic Matrix Composite Blisks from Near-Net Shape Preforms, Phase II

No timely and cost-effective methods now exist for the fabrication of continuous fiber-reinforced ceramic matrix composites (CMCs) of complex geometries. Application of such CMCs can potentially enhance the efficiency and performance, reduce the weight,improve the durability, and lower the cost of aerospace propulsion systems, particularly those used in high temperature, high-stress environments. Achieving these benefits requires development of fiber preform production and matrix infiltration techniquescapable of efficiently producing net or near-net shape parts to eliminate the need for costly and time-consuming machining in the final production step. The quality of such parts will also depend on implementation of improved fiber/matrix interfaces andinterface deposition techniques to weaken the bond between the fiber and matrix and maximize the degree of slip at that interface, a key mechanism for load transfer and overall CMC strength. This feature is key to both oxidation-resistant ceramic fibersand for many projected applications in which carbon fibers are of particular interest as CMC reinforcements due to their relatively low cost, high strength and stiffness, and low density compared to oxide or non-oxide ceramic fibers. The main drawback ofcarbon fibers, however, is their low oxidation resistance, which has prevented their extensive use in high temperature oxidizing environments. Oxide interfaces can potentially impart sufficient protection, as well as provide other essential interfacefunctions, for carbon as well as ceramic fibers. In previous work, Ultramet demonstrated a unique and innovative process for depositing oxide interfaces, specifically ultraviolet-enhanced chemical vapor deposition (UVCVD). Ultramet has also successfullyachieved rapid infiltration of carbide matrices within thin (<0.125