Abstract: 42CrMo steel low-speed shaft thrust ring failed due to end face cracks after quenching and tempering treatment. The chemical composition, hardness gradient and microstructure of the fracture position were observed and detected, and the inclusions in the fracture were observed and analyzed by means of SEM and EDS. The results show that the cracks are caused by many factors, such as the inclusion in raw materials, the existence of rough tool marks on the workpiece surface, and the unreasonable structural design of the low-speed shaft part. The risk of quenching cracking at the thrust ring can be reduced by optimizing the rough turning process of machining, quenching auxiliary tooling and controlling the microstructure of raw materials.

Key words: 42CrMo steel, microstructure, failure analysis, cracking