Reduction of Young's Modulus of Surface Modification Layer of Stainless Steel SUS 316 L by Cavitation Shotless Peening

Abstract

Peening is a technique of surface modification to improve fatigue strength of metallic materials. Cavitation shotless peening (CSP) is the peening method using cavitation impacts and shots are not required. Residual stress and hardness of materials are also changed by CSP. Similarly, Young's modulus of surface improvement layer might be changed by CSP. Young's modulus is one of the main mechanical properties of materials, and indicates material structure, and it is an important parameter for stress measurement by X-ray diffraction. In the present paper, Young's modulus of type 316 L stainless steel peened by CSP was evaluated by measuring natural frequency of cantilever. And, Young's modulus of surface modification layer is evaluated by assuming composite cantilever. It was revealed that Young's modulus of surface modification layer by CSP was decreased about 11%, although Vickers hardness was increased about 40%. Namely, elastically hardness is decreased, and plastically hardness is increased by CSP.