激光熔覆铁基合金对轮轨材料磨损与损伤性能的影响

Effect of laser cladding Fe-based alloy on wear performance of wheel and rail steels

利用CO2多模激光器在轮轨材料表面进行激光熔覆,分析了铁基合金熔覆层的微观组织结构与显微硬度,利用MMS-2A微机控制摩擦磨损试验机研究了激光熔覆处理前后轮轨试件的滚动磨损与损伤性能。结果表明:轮轨试件熔覆处理后,熔覆层主要由共晶组织和枝晶组织组成;受凝固条件影响结合区附近主要为较为粗大的晶体组织,中部至表层出现胞状晶和树枝晶;激光熔覆组织中的Fe与Ni元素形成(Fe,Ni)固溶体,Cr容易与C结合形成硬度较高的碳化物。轮轨材料激光熔覆处理后表面硬度分别提高约122.6%和141.6%,未处理轮轨试件磨损率较高,出现了明显的塑性流变变形且存在明显的疲劳裂纹,磨损机制主要为疲劳磨损;轮轨试件激光熔覆处理明显降低了磨损率,磨损机制主要为轻微疲劳磨损。

Laser clad Fe-based alloy coatings were prepared on surface of wheel and rail materials by a CO2 muhimode laser. Microstructure and micro-hardness of the coatings were analyzed. The rolling wear properties of the untreated and laser clad specimens were investigated on a MMS-2A testing apparatus. The results show that the microstructure of Fe-based alloy coatings is composed of dendrite structure and eutectic structure. Affected by the solidification conditions, the coarse crystal structure is observed in the binding region while the cellu｜ar dendrite and dendrite structure forms in the middle and the surface regions of the coatings. （ Fe, Ni） solid solution and high-hardness chromium carbide are defected. The hardness of laser clad wheal and rail specimens is increased by 122.6% and 141.6% compared with the untreated specimens, respectively. The wear rates of untreated wheel and rail specimens are higher and the wear mechanism is dominated by fatigue wear with obvious plastic deformation and fatigue cracks. The lower wear rates of the laser clad wheel and rail specimens are observed and the main wear mechanism is fatigue wear.