轮轨试样Co基合金激光熔覆层组织及磨损性能

Microstructure and wear performance of laser cladding Co-based alloy coatings of wheel/rail specimens

为提高轮轨材料的耐磨性降低轮轨磨损,利用CO2多模激光器在轮轨试样表面获得Co基合金熔覆层,测试分析了其组织结构性能和显微硬度,利用MMS-2A微机控制摩擦磨损试验机对比研究了激光熔覆处理与未处理轮轨试样的抗磨损性能.结果表明:激光熔覆处理后在轮轨试样表面获得与基体良好结合厚度约1 mm的熔覆层;熔覆层主要由枝晶(γ-Co)和共晶组织(Cr23C6+γ-Co)构成,初生相为γ-Co过饱和固溶体,富含Cr元素,共晶组织中富含Co元素;结合区为粗大柱状晶,从中部到表层出现胞状晶、树枝晶等多种形态.离界面越远组织越细密,组织生长方向紊乱;结合区存在元素扩散,尤其是Fe、Cr和Co含量变化显著;激光熔覆Co基合金后轮轨试样硬度分别提高约52.98%和43.44%,能有效降低对摩副磨损,轮轨抗磨损能力提高约为原来的5倍.

For improving the wear resistance of wheel/rail materials and decreasing the wheel/rail wear, the laser cladding Co?based alloy coating was obtained on the surface of wheel/rail specimens by CO2 multimode laser device. The microstructure and micro?hardness of the coatings were tested and analyzed, and the wear resistance of substrate and the coatings were studied using a MMS-2A rolling wear test apparatus. The results indicate that the cladding coating with thickness of 1mm on the surface of wheel/rail specimens is obtained after laser cladding, which has an excellent metallurgical bonding with the substrate. The coating consists of dendrite (γ-Co) and eutectic ( Cr23 C6+γ-Co) . The prime phase with rich?chromium is dendritic solidγ-Co, while eutectic structure is rich in cobalt. The thick columnar dendrites are observed in the bond zone and there are some other crystallization morphologies such as cellar, columnar from the center to the top surface. The microstructures far from the interface are thinner and grow in disorder. There exist element diffusion in bond zone and the percentage of Fe, Cr, Co change significantly. The hardness of wheel/rail specimens with laser cladding Co?based alloy increases by 52. 98% and 43. 44%. The wear resistance of wheel/rail is improved about 5 times than that of substrate and it would significantly reduce the wear rate of other friction pair without laser cladding.