某20CrNi2Mo钢制齿轮服役一段时间后，齿面出现了较多点坑状缺陷。采用宏观分析、扫描电镜分析、金相检验等方法对该齿轮缺陷出现的原因进行了分析。结果表明：齿面及齿顶凹凸不平的点坑状缺陷均由电蚀所致。电蚀使得局部油膜无法建立，加之电蚀放电后形成高硬、高脆的淬火马氏体，在循环啮合作用下齿轮发生磨损并出现接触疲劳剥落。

Many pit defects appeared on the tooth surface of gear made of 20CrNi2Mo steel after working for a certain time. The causes of those defects were analyzed by macroscopic analysis, scanning electron microscopic analysis and metallographic examination. The results show that the pit defects on the surface and top of gear teeth were caused by electric corrosion. Local oil film cannot be established due to electric corrosion and martensite with high hardness and brittleness formed after electric erosion discharge, which resulted in gear wear and contact fatigue spalling under the cyclic engagement.