飞机电源系统的恒速传动装置齿轮在装机使用124 h后发生断裂失效;用体视显微镜、SEM、EDS等方法进行了分析,用硬度法测定了齿轮接触面的渗碳层深度.结果表明:差动齿轮先发生早期疲劳断裂,其原因是齿根处存在尺寸较大的氧化铝夹杂物,导致应力集中形成了裂纹源,再加上齿根部位渗碳时未形成有效硬化层,导致齿根处疲劳强度大大降低,致使裂纹扩展而断裂;随后输入齿轮发生过载断裂.

Gears of the constant speed drive used in aircraft power system failed after running for 124 hours.For finding the failure reason macro and micro analysis on the fractured gears were performed by means of stereo microscopy,SEM and EDX.The carburized depth of the gear tooth was examined by hardness testing.The results show that early fatigue fracure of the differential gear happened first.Large size aluminium oxide inclusions at the teeth root of the differential gear resulted in stress concentration and formation of crack source.Effective hardening didnt form at the teeth root,resulting in the decrease of the fatigue strength greatly.So the fatigue crack grew and led to the final fracture of the differential gear.Then overload breakage of the input gear occured.