C/HfC Structures for Tactical Propulsion Reaction Jet Control

Rhenium has been successfully demonstrated in solid rocket motor applications because of its high melting point and excellent strength at elevated temperatures. However, rhenium comes with a significant weight and cost penalty when used in monolithic form. Refractory ceramics such as hafnium carbide (HfC) have increased temperature capability and are more chemically inert, but in unreinforced monolithic form they are susceptible to catastrophic thermal shock owing to poor toughness. In prior work for DoD and NASA, Ultramet demonstrated a rapid and 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 (C/ZrC) components have been tested to 5200°F by the Air Force with no erosion. The potential exists to optimize this rapid and inexpensive process technology for solid rocket motor pintles and seats with reinforced HfC. In this project, Ultramet will demonstrate a carbon fiber-reinforced hafnium carbide (C/HfC) material system as an alternative to monolithic rhenium structures for reaction jet control components such as pintles and seats in tactical missile propulsion systems. The C/HfC system will provide superior erosion resistance and strength at elevated temperatures with a density that is only 37% of that of monolithic rhenium and reduced component cost in production. The process development objective of the project will demonstrate the feasibility of rapid and economical net-shape fabrication of fiber-reinforced HfC composite pintles and seats through melt infiltration processing. The material development objective of the project will validate the survivability of C/HfC in a simulated hot gas test. A near-net-shape demonstrator article will be fabricated and delivered to the Air Force at the conclusion of the project.