Influences of Mechanical Properties and Retained Austenite Content on Shot-peening Characteristics

Abstract

Shot peening is used for the material which are high carbon steel such as carburized steel and spring steel as a surface enhance method to increase fatigue strength. The compressive residual stress and work hardening induced by shot peening are important shot peening characteristics to increase fatigue strength. The compressive residual stress and work hardening induced by shot peening are strongly influenced by material property such as mechanical property and retained austenite, and to investigate influence of material property on shot peening characteristics is very important. In this study, we carried out shot peening to chrome steel and chrome molybdenum steel which changed retained austenite volume and mechanical property, and we investigated relationship between shot peening characteristics and material property. As a result, we gained the following conclusions.
1) It was found that materials with a higher rate of change of retained austenite content are more easily hardened by shot-peening because of a larger amount of deformation-induced martensite and work hardening.
2) When there was almost no change in retained austenite content, the maximum compressive residual stress was about 60% of the 0.2% proof stress. A higher rate of change of retained austenite content tended to result in increased maximum compressive residual stress compared to the 0.2% proof stress. This is probably due to the increased 0.2% proof stress of the shot-peened material.