喷丸强化对渗氮40Cr和30CrMo钢疲劳性能的影响

Effect of shot peening on fatigue performance of nitrided 40Cr and 30CrMo steels

对40Cr和30CrMo钢进行渗氮、喷丸等单一强化和渗氮后喷丸的复合强化处理,测定了钢件表层的残余应力与显微硬度,采用升降法确定了1×107循环周次下的疲劳强度。结果表明,渗氮、喷丸和渗氮+喷丸表面强化均可提高40Cr和30CrMo钢疲劳强度,但渗氮后喷丸复合强化的效果最佳。对疲劳试样的断口分析表明,调质未表面强化试样的疲劳裂纹源于表面,而强化试样的疲劳裂纹源于强化层下的次表层。

The residual stresses and microhardness distributions in surface layer were measured for 40Cr and 30CrMo steels by nitriding, or shot peening, or nitriding ＋ shot peening, the fatigue strength for 1 ×107 cycles was determined by stair- step method. The results show that the surface modification by nitrided, shot peened, and nitrided followed ＋ shot peened can increase the fatigue strength compared with quenched and high temperature temped 40Cr and 30CrMo steels, but the enhancement of nitrided followed by shot peened specimens is greatest. Moreover, the fatigue source is located at surface for unstrengthed specimens; whereas, it is located beneath the strengthened layer for surface modified specimens.