C/HfC Structures for Tactical Propulsion Reaction Jet Control, Phase II

Rhenium has been successfully demonstrated in tactical solid rocket motor applications because of its high melting point and strength at elevated temperatures. However, rhenium comes with a significant weight and cost penalty when used in monolithic form. Low-cost refractory ceramics such as hafnium carbide (HfC) have increased temperature capability, lower density, and are more chemically inert, but in unreinforced monolithic form they are susceptible to catastrophic thermal shock owing to poor toughness. In previous work, Ultramet developed and demonstrated a rapid, low-cost melt infiltration process for fabrication of net-shape, fiber-reinforced, high temperature ceramic matrix composites for liquid propellant combustion chambers operating at 4200°F. Melt infiltrated carbon fiber-reinforced zirconium carbide components have been tested to 5200°F by the Air Force with no erosion. In Phase I, Ultramet has successfully developed rapid melt infiltration processing of carbon fiber-reinforced hafnium carbide matrix (C/HfC) composites up to 2 inches thick. The processing is virtually independent of part size and shape, making it applicable for net-shape fabrication of pintles and throats for a broad variety of solid rocket motors. Although hafnium carbide has well-established thermochemical survivability in motors operating with reduced smoke propellants, this project is the first to demonstrate processing for a fiber-reinforced HfC composite. Alliant Techsystems (ATK) has expressed great interest in this technology for high-thrust reaction jet control valves in air-to-air missile attitude control systems and will team with Ultramet in Phase II for material and structure optimization and two series of hot-fire testing in a TC-1 type motor.