Failure analysis of gear wheels

This study consists of a failure analysis of gear wheels mounted on an agricultural machine subject to several breakages in operation. Two gears were the subject of metallographic, compositional and photographic analyzes, as well as micro hardness tests and electron microscope observations. The photographic analyzes clearly highlighted a strong wear of the tooth surfaces. Although the failure mechanism is attributable to fatigue, the classic fatigue morphology patterns on the fracture surface were not visible and this was probably due to the low number of cycles that led to the failure of the gears. The analysis of the composition and microstructure of the steel did not reveal any critical issue. In fact, sulphides were present within the material but not in such quantities as to justify the failure. In conclusion, the material of the wheels did not present anomalies, therefore the causes of the failure of the analyzed parts were to be found in an incorrect design or in their incorrect assembly.