喷丸对18％Ni型超高强度钢低周疲劳性能影响

对C250型18%Ni超高强度钢（C250钢）进行铸钢丸一次喷丸（单喷）和铸钢丸+玻璃丸二次喷丸（双喷），研究喷丸前后的表面形貌、显微组织和低周疲劳性能的变化.结果表明，单喷后C250钢低周疲劳寿命提高了接近2.5倍，而双喷后试样疲劳寿命提高3倍.喷丸表面的亚晶粒细化是提高低周疲劳性能的主要因素，二次喷丸带来的平滑化效果进一步提高了低周疲劳性能.平滑化效果减小了表面应力集中程度，使经过双喷后试样疲劳断口为单源疲劳断口，而未喷丸试样和单喷试样的低周疲劳断口呈现多源疲劳状态.

Effect of shot-peening on low-cycle fatigue property of 18% Ni ultra-high strength steel

18% Ni ultra-high strength steel C250 was employed to investigate the effect of single shot peening (SSP) with cast-iron bead and double shot peening (DSP) with cast-iron bead and glass bead on surface topography, micro-structure and low-cycle fatigue (LCF). The results show that the low-cycle fatigue life has risen by nearly 2.5 times due to SSP, however, the low-cycle fatigue life after DSP increases by 3 times. Moreover, the sub-grain refinement after peening is the main factor which extends the LCF life, and the smooth surface caused by DSP promotes the LCF property. Furthermore, by comparison with fatigue fracture of unpeened and SSP sample presenting multi-source crack initiations, the DSP one fractured with only one source due to the smooth surface.