Failure analysis of the exhaust valve stem from a Waukesha P9390 GSI gas engine

Abstract A failure occurred of the exhaust valve stem from a Waukesha P9390 GSI gas engine. The valve failed as a result of overheating. The significant hardness loss and the extensive surface oxidation and fretting/galling on the valve stem were indicative of the overheating. The fatigue properties of the alloy dropped due to the over aging and the over temperature. This led to multiple fatigue crack initiation followed by rapid crack propagation to failure.