Cracking Cause Analysis of Gear Shaft

A gear shaft cracked after stored for a while. In order to determine its failure mode and cause, macro and micro observation, microstructure examination, hardness testing, energy dispersive X-ray spectroscopy analysis and hydrogen content testing were carried out. The results indicate that the failure mode of the gear shaft is delayed brittle cracking induced by hydrogen embrittlement. The hydrogen content has little effect on the cracking of the gear shaft There is a large Al₂O₃•(CaO)_X inclusion defect at the source zone, resulting in greater stress concentration, which is the main cause for the brittle cracking. It is suggested that the quality of the material should be seriously controlled so that such failure can be prevented.