U71Mn轨道表面激光再制造FeCrNiB覆层工艺与组织性能

针对U71Mn轨道表面磨损及激光再制造的表面耐磨性不足、气孔缺陷易发等再制造难点,提出并验证了脉冲激光熔覆制备轨道表面FeCrNiB覆层的工艺与方法。试验结果表明：熔覆层顶部主要分布细小致密的等轴晶、中部交错存在较多的树枝晶,树枝晶晶粒具备长大条件已存在初次晶臂和二次晶臂,覆层低部呈现出的胞状晶组织,大致垂直于界面；熔覆层中Cr₇C₃硬质相和纳米级极细粒状和片状珠光体组织的存在,使熔覆层具有较高硬度及耐磨性,熔覆层的平均硬度由310 HV_0.2提升至750HV_0.2；在同等的摩擦磨损条件下,熔覆层的耐磨性提高了5倍；对接试样的抗拉强度略小于基体抗拉强度,但仍能满足钢轨使用要求。

Process and microstructure properties of U71Mn FeCrNiB Coating by laser Remanufacturing

Aiming at the remanufacturing difficulties of U71Mn track surface wear, low surface wear resistance and easy porosity defects caused by laser remanufacturing, the technology and method of preparing FeCrNiB coating on track surface by pulse laser cladding were proposed and verified. The results show that the top of the cladding layer is mainly distributed with fine and dense equiaaxial crystals, and there are more dendrites in the middle of the cladding layer. The dendrite grains have primary and secondary crystal arms, and the lower part of the cladding layer presents a cellular crystal structure, which is roughly perpendicular to the interface.The existence of Cr₇C₃ hard phase and nano-sized granular and flake pearlite structure in the cladding layer makes the cladding layer have high hardness and wear resistance, and the average hardness of the cladding layer increases from 310 HV_0.2 to 750HV_0.2.Under the same friction and wear conditions, the wear resistance of the cladding layer increases by 5 times.The tensile strength of butt sample is slightly less than that of matrix, but it can still meet the requirements of rail.