喷丸强化对17-4PH不锈钢室温及高温疲劳性能的影响

Surface strengthening of 17-4PH stainless steel with different shot peening (SP) strengths was studied in the present paper. Variation of surface residual stress, surface morphology and surface hardness were investigated by X-ray diffraction (XRD), optical microscopy (OM) and microhardness tester. The effects of different temperature fields on fatigue properties of SP 17-4PH stainless steel were studied by fatigue test and scanning electron microscopy (SEM). The results show that low strength SP can significantly improve the fatigue life of 17-4PH at room temperature by introducing residual stress field and retaining surface integrity. With the increase of SP strength, the surface roughness increases and the depth of working hardened layer tends to increase. However, when SP strength exceeds the medium strength level, the surface hardness no longer increases. In terms of fatigue life, different temperature fields have distinct effects on SP 17-4PH steel. When the ambient temperature is lo-wer than 300℃, the fatigue life of 17-4PH could be significantly increased by SP treatment, while the fatigue performance would be obviously reduced when the temperature is higher than 450℃. Further analysis shows that the decrease of high temperature fatigue properties of 17-4PH results from the serious relaxation of residual stress and the decrease of surface integrity.