Abstract
The effects of normal shot-peening (SP) and hard shot-peening (HSP) on the fatigue properties and material properties of SUS316L austenite stainless steel were investigated. The rotating bending fatigue tests at 50Hz in air and under water cooling conditions were carried out on the SP and HSP treated and the non-shotted SUS316L specimens. In air condition, the fatigue strength of the SP and HSP treated materials were improved, but the specimens became heated because of internal friction. The fatigue strength under water cooling condition was improved on the SP and HSP treated SUS316L. The fatigue limit of 108 and the fatigue strength in all lives of the HSP treated materials were highest in comparing with the SP and the non-shotted materials. X-ray diffraction measurement and hardness tests were also carried out on the SP and HSP treated SUS316L. The results showed that there existed the hardening layer caused by plastic deformation and the high compressive residual stress in the surface layers of the SP and HSP treated materials. Fatigue crack origins were transferred from the surface to the subsurface by the surface hardening and by the compressive residual stress. For the fatigue strength improvement, the HSP treatment of austenite stainless steel was very successful.
