Effect of micro-shot peening on fatigue properties of precipitate strengthened Cu-Ni-Si alloy in air and in salt atmosphere

Abstract In this study, the precipitate strengthened Cu-Ni-Si alloy was micro-shot peened by ceramic balls with a diameter of 40 μm. The fatigue tests using the peened specimens were conducted in air and in salt atmosphere respectively. The results show that a fine and hardening layer is formed on the surface of peened specimen and the compressive residual stress is introduced. There is no fatigue limit for specimens in both test conditions. The S-N curve of specimens in salt atmosphere shows a continuous decrease with the increasing number of loading cycles, while that in air shows a step-wise shape. Compared with the un-peened specimens, the fatigue strengths of specimens at 10 7  cycles are increased by 47% and 67% in air and in salt atmosphere respectively. The peened specimens in air condition failed from subsurface zone in high cycle fatigue region, while all the other specimens failed from surface. The micro-shot peening can improve the surface property and delay the crack initiation and propagation, so as to enhance the fatigue strength greatly.