Stress Corrosion Cracking of Tough Pitch Copper in a Bolting Application

Abstract

Stress corrosion cracking was observed in C11000 and C10200 copper electrical feedthrough pins used in a bolting application. The component provided the balancing tensile stress required for compression of a gasket seal of a refrigeration compressor. The component, as designed, had functioned without failure for years of production and thousands of units. The fractures were mixed brittle intergranular with ductile microvoid dimples. An extensive analysis of actual failed samples as well as a process of elimination methodology indicated that the fractures were due to SCC by an unidentified chemical species within the sealed compressor chamber. A unique combination of applied stress, residual stress, a stress riser, and fine-grain size isolated the failure mechanism to a single production lot of material.