Failure of Dowel Bolts in the Bevel Gear Assembly of an Aeroengine

摘要

A set of six dowel bolts made of a nickel-chromium-molybdenumudsteel, holding together a bevel gear and a spur gear in an aero engine, failed in service . This led to the separation of the two gears and disruption of drive to the various accessories of. the engine, resulting in an accident. Failure analysis revealed that the bolts had , failed by hydrogen embrittlement, the hydrogen pick up occurring during the phosphating treatment.