Investigations of a damage origin in a gear wheel

Abstract

In this diploma thesis, a broken car gear wheel has been evaluated to determine the damage origin of its failure. In the theoretical part, case hardening process was described including important defects in carburized layers as well as the main origins of gear wheel damages. In the experimental part, metallographic, fractographic and micro-hardness analysis was used to determine the origin of the gear wheel failure. The investigations have been performed on samples after an accelerated lifetime test. The experimental results showed two different kinds of defects: quenching cracks and rolling contact fatigue, mainly due to improper quenching and very high shear stresses during the lifetime test.