Brazed Copper Electrical Ring Failure via Hydrogen Reaction Embrittlement

Multiple fractured ring copper segments with brazed brackets were submitted for failure analysis. The rings carry electrical current and are part of a larger three-phase electrical assembly in a wind generator application. The rings failed prematurely in service, resulting in downtime and costly repairs. Failure of q ring occurs via a through-wall cross-section fracture, typically within an inch from the end of two of the three brazed brackets. Repair or replacement of the rings must be done onsite. Brazing repairs are common and are performed using a hydrogen torch procedure. An analysis of braze quality and brazing practices was performed in the investigation. It was determined that the copper ring assemblies failed prematurely in service due to hydrogen-assisted cracking in the form of hydrogen reaction embrittlement (HRE). Mechanisms responsible for the failure mode and implications of selected repair methods are discussed, along with ways to prevent this type of failure in the future. Analysis techniques employed during the investigation include scanning electron microscopy, metallographic evaluation, and chemical analysis.

Keywords: failure analysis, copper alloy, hydrogen reaction embrittlement, brazing, repair, microscopy.