Fracture Analysis of the Water Pump Shaft

A water pump shaft broke after it had been under service for only 8 months.According to a series of test analysis such as chemical constituents,mechanical properties,metallographic structure,macrofractography and scanning electron microscopy,it was concluded that the fracture was caused by large clearance between impeller and pump shaft,so that the circumferential stress at key slot increased and fatigue source formed.Primarily,circle fatigue developed into chipping,and then developed into radial rotating and bending before fracture finally occurred.