Fracture Analysis of Rotating Shaft of Impeller

The rotating shaft of an impeller fractured during working. Macro and micro observation, size measurement, macro and microstructure examination, chemical composition analysis, hardness and mechanical properties testing were carried out to find out the cause for the fracture. In addition, integrity analysis was conducted for the related components. The results show that the failure mode of the rotating shaft is fatigue fracture. Cracks initiated at the bottom of the grinding wheel groove. The main cause for the cracking is the unbalanced load on the impeller. The hardness and strength of the shaft is higher, promoting the initiation and propagation of the cracks. It is suggested that rough turning should be performed on the steps of the shaft before quenching or the heat treatment process should be adjusted so that the microstructure of the cracking source zone can be improved and the fatigue life can be increased.