层流等离子体点状淬火面积比对轮轨材料磨损性能的影响

Influence of Laminar Plasma Spot Quenching Area Ratio on Wear Properties of Wheel/Rail Materials

目的运用层流等离子体点状淬火工艺,提高轮轨材料的耐磨性,并探究最佳的表面处理面积比率。方法采用层流等离子体点状淬火方式,对高速轮轨材料进行表面处理,利用MJP-30型滚动接触磨损试验机,对4组不同点状淬火面积比(0%、15%、30%、45%)的轮轨试样进行滚动接触磨损试验,利用金相显微镜、扫描电子显微镜(SEM)、硬度计等对轮轨试样进行磨损形貌表征和耐磨性分析。结果层流等离子体点状淬火可获得板条状马氏体组织,轮轨材料表面硬度提升200%以上,磨损率降低80%以上。当面积比为30%时,轮轨材料的磨损率最小,相比于未处理试样,总磨损率下降约89.2%,车轮的磨损率降低约89.6%,钢轨降低约88.7%。对磨损试验后的轮轨试样进行表面损伤分析和截面显微组织观察,结果表明,点状淬火试样表面损伤显著减轻,剥离和裂纹主要集中在淬火过渡区域,淬火区域可以显著抑制材料的塑性变形,淬火区和基体结合层可抵抗裂纹的进一步扩展。当面积比为30%时,轮轨试样的耐磨性能最佳。结论层流等离子体点状淬火可有效提高轮轨材料的耐磨性,最佳的淬火面积比为30%左右。

This work aims to apply laminar plasma spot quenching process to improve the wear resistance of wheel/rail materials and to explore the best surface treatment area ratio.The surface of high-speed wheel/rail material was treated by laminar plasma spot quenching,four groups of wheel/rail samples with different spot quenching area ratio(0%,15%,30%and 45%)were tested by MJP-30 rolling contact wear tester.The wear morphology and wear resistance of wheel/rail samples were characterized by metallographic microscope,scanning electron microscope(SEM)and hardness tester.The results showed that laminar plasma spot quenching can obtain dense lath martensite structure,the surface hardness of wheel and rail materials increased by more than 200%and the wear rate decreased by more than 80%.When the area ratio is 30%,the wear rate of wheel/rail material is the smallest.Compared with the untreated sample,the total wear rate is reduced by 89.2%,the wear rate of wheel is reduced by 89.6%,and the wear rate of rail is reduced by 88.7%.The characteristics of surface damage and section microcracks of the wheel and rail samples after the wear test showed that the surface damage of the spot quenched samples was significantly reduced,and the spalling and crack were mainly concentrated in the quenching transition region.Importantly,the quenching region could obviously inhibit the plastic deformation of the material,the quenched region and the matrix bonding layer can resist further crack propagation.When the area ratio is 30%,the wear resistance of the wheel/rail samples is the best.It is concluded that laminar plasma point quenching can effectively improve the wear resistance of wheel/rail materials,and the quenching area ratio of about 30%is the best surface treatment process.