FAILURE ANALYSIS ON THE EXHAUST VALVE OF SHIP DIESEL ENGINE

The microstructure and crack forms of the exhaust valve of the diesel engine were observed,and the chemical compositions of the valve material and corrosive products in the cracks were examined. The results indicated that material of exhaust valve have not defect. It is pointed out that stress corrosion action of S and V oxidation on the seal surface of the exhaust valve was main reason that resulted in cracks in exhaust valve. The brush of high temperature gases and the effect of impact load accelerated the exhaust valve failure.