Evaluation of the Degradation of Combustion Engine Valves

This work aims at the description of the degradation of the intake and exhaust valve of the combus-tion engine during operation. For the experiments, new valves from Ford Fiesta were used, as well as the used ones with known mileage. In order to simulate the valve long-term operation and to esti-mate the temperature of the valve during the use, the new valves were annealed at 700 – 900 °C for 1000 h (corresponding to the mileage of 70,000 km with average speed of 70 km/h) and the grain size was compared with the used valves. It was found that this model experiment can easily predict the operation temperatures of the exhaust valves, which were made of the heat-resistant austenitic steel. However, the metallography procedure for the determination of the grain size fails in the case of the martensitic steel valves.