高速中间轴齿轮开裂失效分析

Cracking failure analysis on high-speed intermediate shaft gear

某齿轮箱中的18CrNiMo7-6钢高速中间轴齿轮在渗碳淬火磨齿后做动平衡试验过程中出现振动异响,拆机后发现中间轴齿轮在轴径处出现明显的轴向裂纹。通过宏观观察、多次切割后找到裂纹源位于大轴齿轮心部,在裂纹源处取样进行化学成分、显微组织分析等方法对开裂位置进行研究。结果表明,由于大型齿坯锻件去氢处理不完全,随着时间的推移,氢原子聚集形成氢分子,在工件内部造成应力集中,导致该轴齿轮在渗碳淬火磨齿后发生延迟性氢脆开裂,引起轴齿轮失效。

A 18CrNiMo7-6 steel high speed intermediate shaft gear of gearbox had abnormal vibration sound during the dynamic balance test after carburizing and quenching.After disassembly,it was found that the intermediate shaft gear had obvious axial crack at the axial diameter.After macro observation and multiple cutting,it was found that the crack source was located at the axle center of the large gear.The crack location of the main shaft was studied by chemical composition analysis and microstructure analysis.The results show that due to the incomplete dehydrogenation treatment of the large billet forgings,the hydrogen atoms gather to form hydrogen molecules over time,which causes the stress concentration inside the workpiece,leading to the delayed hydrogen embrittlement cracking of the gear shaft after carburizing and quenching,and resulting in the failure of the shaft gear.