某型磁浮列车制动闸片的磨损失效分析*

北京某地铁线路磁浮列车的制动闸片在服役约10天后,表面就出现了严重的凹坑和沟槽,显示过度磨损。对闸片的损伤区进行宏微观的形貌分析、化学成分分析、白光干涉测试分析和X射线光电子能谱分析,讨论铜基粉末冶金制动闸片的损伤特征,分析损伤失效原因,并对其如何降磨提出建议。结果表明:闸片服役后表面损伤严重,出现较深的沟槽,且高温烧伤痕迹明显,其损伤机制主要有电气磨损、磨粒磨损、黏着磨损、氧化磨损以及疲劳磨损;基体材料缺失严重,其中的Cr合金明显断裂,因Cr合金硬度很高,在脱落后会对闸片造成严重的磨粒磨损;闸片内部存在较多裂纹,这些裂纹发生在石墨与基体的连接处,其中体积较大的石墨边缘均有很深的裂缝,极易产生裂纹或加剧裂纹的扩展,建议适当降低石墨的粒度。

Analysis on Wear Failure of Brake Block of Magnetic Suspension Train

After the running of ten days in a magnetic train of Beijing,the surface of the brake block has very serious pits and grooves,indicating excessive wear.Macro and micro-morphology analysis,chemical composition analysis,white light interference analysis and X ray photo electron spectroscopy analysis were carried out on the damaged area of the brake block,and the damage characteristics of brake pads of Cu-based powder metallurgy materials were discussed.The causes of damage failure were analyzed,and some suggestions on how to reduce wear were put forward.The results show that the surface damage of the brake block is serious after service,the deep groove can be observed by macroscopic analysis,and the high temperature burn marks are obvious.The main damage mechanisms are electrical wear,abrasive wear,adhesive wear,oxidation wear and fatigue wear.The matrix material loss is serious,and the Cr alloy is obviously fractured.Due to the high hardness of the Cr-alloy,it will cause serious abrasive wear to the brake block after falling off.There are more cracks inside the brake block,these cracks mainly occur at the junction of graphite and matrix,in which the larger graphite edges have deep cracks,which are easy to produce cracks or aggravate the crack propagation.It is suggested to reduce the particle size of graphite appropriately.