利用宏观检验、断口分析、化学成分分析、金相检验以及硬度检测等方法，对42CrMo钢挖掘机销轴的断裂原因进行了分析。结果表明：销轴断裂为双向弯曲疲劳断裂。由于销轴表面存在较脆的白亮层ε相，且白亮层分布有较严重的疏松，增加了销轴表面的脆性，使销轴表面形成了较多的微裂纹，导致了疲劳裂纹的萌生；销轴的渗氮层深度和硬度偏低也降低了销轴的疲劳强度，加速了疲劳裂纹的扩展，最终使销轴发生早期疲劳断裂。

By means of macroscopic examination, fracture analysis, chemical composition analysis, metallographic examination, hardness testing and so on, the fracture reason of 42CrMo steel excavator pin was analyzed. The results showed that the pin fracture mode was biaxial bending fatigue fracture. There was the brittle white layer ε phase on the pin surface, and the brittleness of the pin surface increased by the serious loose on the white layer, the microcracks on the pin surface led to the fatigue crack initiation. The fatigue resistance of pin reduced by the low nitrided layer depth and hardness of pin, that accelerated the fatigue crack extension, and the early fatigue fracture of pin happened at last.