对锁紧轴渗氮后断裂的原因进行了分析,检测了渗氮前后的硬度、断裂韧性及金相组织。研究结果表明,锁紧轴调质后的不良组织导致整个轴韧性下降,硬度升高,对裂纹敏感。氮化并未引起调质后氮化层以外的其它部位组织和性能发生明显变化。退刀槽根部圆弧过渡不完全,尖角易产生应力集中,断裂易产生在应力集中处。针对以上问题提出改进措施。 The reason of fracture after nitriding was analyzed, and the hardness, fracture toughness and microstructure before and after nitriding were measured. The results show that the poor quality of the mandrel after quenching results in the decrease of the toughness of the entire shaft, the increase of the hardness and the sensitivity to cracks. Nitriding does not cause any significant changes in the microstructure and properties of the parts other than the nitrided layer after the tempering. Undercut groove arc transition is not complete, easy to produce sharp stress concentration, fracture easily occur in the stress concentration. In view of the above problems put forward improvement measures.