20CrNiMo钢销轴在服役过程中轴身部位发生断裂。采用化学成分分析、断口分析、金相检验和硬度测试等方法对销轴断裂原因进行了分析。结果表明：该销轴断裂为应力集中条件下的多源疲劳断裂，销轴轴身外表面经激光打标后产生二次淬火组织、二次回火组织和结晶裂纹，在安装和服役载荷的共同作用下，销轴轴身断裂。

The fracture occurred at the shaft body of 20CrNiMo steel pin shaft in service. The fracture reasons were analyzed by chemical composition analysis, fracture analysis, metallographic examination and hardness test. The results show that the fracture of the pin shaft was a multi-source fatigue fracture under the condition of stress concentration, after laser marking, the outer surface of the pin shaft produced secondary quenching structure, secondary tempering structure and crystal cracks, under the combined action of installation and service load, the pin shaft body propagated along the crystal crack till fatigue fracture.