Únavové poškození cementovaných ozubených kol pro převodovky

Abstract

This bachelor thesis is focused on fatigue damage of steels, specifically fatigue of gear wheels used in automotive industry and thermo-chemical processing of gear wheels. The theoretical part is focused on the thermo-chemical processing in general. Basic principles of case hardening of steels are described here. Furthermore, fatigue damage of steels is characterized with a special attention paid to different stages of fatigue process. The experimental part is devoted to the fractographic and metallographic analysis of the gear wheel where some teeth were broke off. Analyses of cemented layer microstructure, core microstructure, hardness of carburized layer and fractographic analysis were carried out on the damaged wheel. It was found out that the studied wheel was degradated by fatigue process initiating by intergranular sub-surface oxidation formed during carburizing process.