Failure Analysis of Internal Combustion Exhaust Valve

The exhaust valves system is very important for internal combustion engines and experienced severe physical and chemical environment including frequent impact, high and varying temperature, exhaust gas' chemical corrosion and deposition of fine dust, et al. This paper presents a failure analysis of two new internal combustion exhaust valves used not more than 200 houses. The fracture surfaces were investigated by SEM and optical microscope. And EDS was used the clarified the related chemical elements. Results of present investigation showed that instability of oxidation film that formatted on the seal face during the early stage, was a crucial factor of the failure. In this case, the film was thin and porous, so high temperature exhaust gas could reaction with matrix welding layer. Consequently, the welding layer loses its wear resistant property during the subsequence service procedure.