Influence of Inclusion Type on Internal Fatigue Fracture under Cyclic Shear Stress

Abstract Four kinds of high carbon chromium steel were conducted to ultrasonic torsional fatigue test and the fracture surfaces and the cross-sections of fracture origin were observed. Internal fatigue fracture was occurred from oxide inclusion and MnS, and ODA was found surrounding inclusion. The behaviors of the crack initiation and propagation were different depending on inclusion types. Thus the characteristics of inclusion influence to fatigue properties.