Failure Analysis on Fracture of an Engine Valve Spring

Early fracture reasons of an automotive engine valve spring were investigated by means of macro and micro analysis,metallographic examination,micro hardness test and chemical compositions analysis.The results indicate that the failure property of the spring was fatigue fracture.The pockmark defect on the spring surface caused by electric arc burn during salt bath quenching heating was the root cause for the early fatigue fracture of the valve spring.