Failure analysis of impeller removed from a turbocharger

An impeller had failed catastrophically after 7 years in service. Failure analysis of the impeller was conducted using optical microscope, Scanning Electronic Microscope (SEM), tensile mechanical testing equipment and OES metals analyzer. It was found that the impeller was a low stress high cycle fretting fatigue failure with multiple transverse cracks initiating from the bore surface. Multiple radial cracks were final fast overload failures resulting in the catastrophic failure.