LOW-COST COMPOSITION GRADIENT MATERIALS FOR UNCOOLED ROCKET NOZZLES

The proposed Phase I project will examine low cost, low density composition gradient materials for zero-erosion rocket nozzles for use at the extreme temperatures encountered with aluminized propellants. The materials system consists of a C fiber-reinforced HfC matrix composite substrate overcoated or infiltrated with WC and finally coated with high purity W metal. Cylindrical geometry substrates will be produced via liquid infiltration/pyrolysis techniques. Surface layers will be produced by chemical vapor deposition on the inside of the cylinder using an existing apparatus. Screening tests will be performed to verify physical and mechanical properties. Specimens for erosion testing will be provided to the sponsor. Analytical studies of environmental effects on the composition gradient materials and self-degradation reactions such as C transport will support the experimental studies. In an optional task, C-HfC nozzle substrate material will be coated with Re instead of W.