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采用轴与齿轮联体设计制造经高频调质热处理的40CrNi传动齿轮在服役期间发生了提前失效开裂。采用金相显微镜分析显微组织,扫描电镜观察断口,显微硬度计测量硬度。结果表明:齿轮心部显微组织为块状铁素体+片层珠光体+少量粒状珠光体。40CrNi传动齿轮提前失效开裂的原因是调质处理加热温度低,冷却速度慢,齿轮未淬透;机加工引起了疲劳裂纹的萌生,疲劳源是由粗糙机加工引起的应力集中而形成;热处理工艺未能使力学性能达到良好的抗冲击性、抗疲劳性要求,最终导致疲劳断裂。
The use of shaft and gear joint design and manufacture of high-frequency quenched and tempered 40CrNi drive gear occurred during service failure early cracking. The microstructure was analyzed by metallographic microscope, the fracture was observed by scanning electron microscopy, and the hardness was measured by microhardness tester. The results show that the heart of the gear is composed of massive ferrite + lamellar pearlite + small amount of granular pearlite. 40CrNi transmission gear failure due to premature cracking is quenched and tempered low heating temperature, slow cooling, gear not quenching; Machining caused by fatigue crack initiation, the fatigue source is caused by rough machining stress concentration formed; heat treatment process Failed to achieve good mechanical properties of impact resistance, fatigue resistance requirements, and ultimately lead to fatigue fracture.