某4340钢齿轮在试验台上运行4 h后发生断齿,通过宏观观察、渗透检测、磨削烧伤检测、金相检验、化学成分分析、非金属夹杂物评定、平均晶粒度评定、硬度测试、渗氮层深度测定、扫描电镜和能谱分析对齿轮断齿原因进行了分析。结果表明:由于齿轮在运行前已存在淬火裂纹,在齿轮运行过程中啮合受力,裂纹扩展导致断齿。

The gear teeth of 4340 steel fractured after tested for about 4 hours on the testbed. The causes of the broken teeth were analyzed by macroscopic observation, dye penetrant test, low magnification test, grinding burn test, metallographic examination, chemical composition analysis, non-metallic inclusion evaluation, average grain size evaluation, hardness test, nitriding layer depth test, scanning electron and energy spectrum analysis. The results show that quenching cracks which had existed before the operation of the gear propagated due to meshing force during the operation until fracture.