BLANCHING RESISTANT CU-CR COATING BY VACUUM PLASMA SPRAY

Copper alloy rocket engine combustion chamber linings have been found to deteriorate when exposed to cyclic reducing oxidizing (redox) envir onments, which are a consequence of the combustion process. The deteri oration, known as blanching, can be characterized by increased roughne ss and burn-through sites in the wall of the combustion chamber lining and can seriously reduce the operational lifetime of the combustion c hamber. A Cu-30 vol.%Cr coating produced by vacuum plasma spraying was effective in protecting the copper alloy substrate against blanching. The coating properties were characterized after cyclic oxidation expo sure to 650 degrees C in air followed by high pressure hydrogen chargi ng. When exposed to an oxidizing environment at high temperatures, the coating formed a protective chromia scale that was substantially unre duced by high pressure hydrogen.