Fretting Fatigue Fracture Surface of Structural Steels
Hiroshige YAMAMURA, Yoshikazu YAMADA and Ryuichiro EBARA
Abstract:Fretting fatigue tests were conducted on structural steels such as SCM415H,SCM440 and SAPH45 and cast iron FC25. Consequently, it was clarified that the stress over the contact area where fretting failure initiate was dependent on the Vickers hardness number of the steel surface. It was also clarified that the repeated bending stress at the contact area where fretting fatigue failure initiate linearly decreased as stress over the contact area increased. The stress over the contact area where fretting fatigue failure initiate was increased by eighty percent in application of Defric coating to SCM440. Striation, fretting debris and pit were predominantly observed on the surface of the contact area. Crack initiation mode was transcrystalline on SCM440 and SAPH45Aand was intergranular on SCM415H. It can be concluded that the fretting fatigue crack initiate from a pit formed at the contact area due to slip movement. Key Words:Fretting fatigue, Structural steel, Contact area, Pit, Striation, Intergranular fracture