20CrNi_2Mo齿轮传动轴局部剥落失效分析

Failure Analysis of Parts of 20CrNi_2Mo Gear

通过对 2 0 Cr Ni2 Mo齿轮传动轴斜齿轮局部剥落处进行宏观分析和微观断口分析 ,对比剥落处与完好处的宏观硬度与显微硬度分布以及金相组织和渗层深度 ,结合磁粉探伤检验结果。结果表明 :齿轮轴经过渗碳热处理 ,在随后的机械磨齿过程中 ,由于磨削过多 ,致使渗层只有 0 .5 mm,达不到技术要求。齿轮在交变接触应力的作用下 ,首先在齿面产生极小的显微裂纹 ,小裂纹进一步扩展 ,最终造成齿面剥落。

The failure analysis of parts of 20CrNi 2Mo gear is described by macroscopical and microscopical analyses. The hardness of the good and bad parts is analyzed by their metallography organization and carburization layer lenger magnetic powder flaw detection test. Result shows that the failure is caused by the too thin carburization layer(less than 0.5 mm) during the long time mechanical wear-tear after carburization. It doesnot meet the minimum technical requirement and leads to the microcrack on the surface of the gear during the effect of contact stress. The microcrack is then spread. Finally the surface of the gear is exfoliated and the failure is called contact fatigue failure.