Hydrogen damage in friction welded copper joints

The occurrence of hydrogen attack in electrolytic copper and in copper deoxidized with phosphorous, during model heating in oil and in friction welded specimens was investigated. Dissimilar-metal joints, i.e. copper/TZM (titanium–zirconium–molybdenum based alloy) joints and copper/austenitic steel joints, were subjected to microstructural examinations and tensile strength tests. Microcracks near the weld surface, caused by hydrogen attack, were found to occur in the friction welded dissimilar-metal electrolytic copper joints subjected to resoaking at a temperature of 500 °C. This phenomenon did not occur in the joints made using deoxidized copper. The tensile strength of the dissimilar-metal copper joints was tested before and after the additional soaking. It was found that the tensile strength of the friction welded electrolytic copper/steel and electrolytic copper/TZM joints considerably decreased after the additional soaking.