Influences of Fine-Particle Bombarding and Conventional Shot Peening on Surface Properties of Steel

Abstract

This study was conducted to investigate the influences of fine-particle bombarding (FPB, maximum diameter of collision particles: 34 µm) and conventional shot peening (510 µm) on the surface properties of steel. The influence of injection pressure in FPB was also examined. The microstructures near surfaces were nano-crystallized by FPB and shot peening. Grain size of nano-crystals was more markedly decreased by FPB than shot peening, and further reduced by the use of high injection pressure in FPB. Surface hardness increased as the grain size of nano-crystals decreased. The hardened layers of the FPBed materials became thicker by the use of high injection pressure; however, they were still shallower than the hardened layers of the shot-peened materials. Compressive residual stress measured on surfaces was higher in FPBed materials than in shot-peened materials. The use of high injection pressure in FPB was not effective to further increase this stress.