Effect of Young's Modulus of Shot Peening Media on Surface Modification Behavior by Micro Shot Peening

Author:  Toshiyuki Sawada
Source:  ICSP-13
Doc ID:  2017112
Year of Publication:  2017
Abstract:  
Introduction: Micro shot peening that is carried out by using fine peening media is a surface treatment to improve various high strength parts by obtaining compressive residual stress and a nanocrystal layer on a peened surface. It is widely known that higher peening effects can be obtained by using media with higher hardness. For example, it was reported that the large maximum compressive residual stress could be obtained by using harder media [1]. Also, it was reported that a thicker nanocrystal layer was generated by using media with high hardness compared with conventional steel media [2]. On the other hand, there is no report which purely discusses effects of Young's modulus of media on shot peening effects. One reason why there is no report about Young's modulus is supposed that investigating pure effects of Young's modulus is difficult, because there is no suitable pair of conventional media to investigate them. In other words, there is no pair of media which are similar in hardness, density and shape, but different only in Young's modulus as shown in table 1. However, in the case of metal media, because of their changeable hardness, it is supposed to be able to adjust their hardness value by heat treatment in an appropriate condition. So, high speed steel media and FeCrB media [3] were chosen as candidates for this work. Young's modulus of the high speed steel media and the FeCrB media, which were measured by P/M materials, were 221 and 290 GPa, respectively. Then, these media after heat treatment for adjusting hardness showed similar hardness, density and particle shape, but only different Young's modulus.