Friction stir welding of GRCop-84 for combustion chamber liners

GRCop-84 is a copper-chromium-niobium alloy developed for liquid rocket engine combustion chamber liners. GRCop-84 exhibits superior properties over conventional copper-based alloys in a liquid hydrogen-oxygen operating environment. A program to demonstrate scale-up production capabilities of GRCop-84 to levels suitable for main combustion chamber production for the prototype rocket engine was undertaken. This paper describes a novel method of manufacturing the main combustion chamber liner. The process consists of several steps: extrude the GRCop-84 powder into billets, roll the billets into plates, bump form the plates into cylinder halves, and friction stir weld the halves into a cylinder. The cylinder is then metal spun formed to near net liner dimensions, followed by finish machining to the final configuration. This paper describes the friction stir weld process development, including tooling and nondestructive inspection techniques, culminating in the successful production of a liner preform completed through spin forming.