尖轨作为道岔的重要部件,工作环境恶劣,易出现表面磨损、剥离掉块等缺陷。激光熔覆技术可以显著提高尖轨表面的硬度,从而提高其表面耐磨性,减少表面伤损,延长尖轨的使用寿命。采用半导体激光熔覆工艺,在U71Mn道岔尖轨表面制备了Fe-W-Cr铁基复合激光熔覆层,对熔覆层的组织形貌、物相组成及元素分布进行了检测,并对其硬度、冲击性能与摩擦磨损性能进行了分析。结果表明:铁基熔覆层无明显缺陷,且与道岔尖轨形成了冶金结合,熔覆层内大部分区域为树枝晶,在晶界处分布着网状碳化物;熔覆层的平均硬度为876.8 HV(道岔尖轨用钢为252.3 HV),冲击韧度为2.30 J/cm 2,平均摩擦因数为0.31(道岔尖轨用钢为0.63);在同等的摩擦磨损条件下,铁基熔覆层的磨损量为0.0043 g,仅为道岔尖轨用钢(0.0408 g)的10.54%。半导体激光熔覆工艺使得道岔尖轨表面的硬度及耐磨性能得到了显著提高,从而使其服役性能得到了明显改善。

The railroad switch is an important part of turnouts. The surface of the switch rail could be easily worn and peeled because of its poor working condition. Laser cladding technology can significantly improve the surface hardness of the railroad switch, and the wear and surface damage resistance as well as service life are accordingly improved. A Fe-W-Cr composite coating was successfully prepared on the surface of U71Mn railroad switch using high-power semiconductor laser cladding technology. The microstructures, phase formation and elemental distribution of the coating were tested, and the hardness, impact toughness, and friction and wear properties of the coating were analyzed. Results show that there is no pore, crack or other defect in the coatings, and the metallurgical bonding between the coatings and the substrates are effectively established. The dendrite structures exist in most of the region on the coating, and networks of carbides are distributed around the grain boundaries. The average hardness of the coatings is 876.8 HV (the hardness of railroad switch rail is 252.3 HV), the impact toughness is 2.30 J/cm 2, and the friction coefficient is 0.31(the friction coefficient of railroad switch rail is 0.63). Under the same friction and wear condition, the wear loss of the coating is 0.0043 g, which is only 10.54% of the substrate (the wear loss of substrate is 0.0408 g). The hardness and wear resistance of the railroad switch are significantly enhanced using laser cladding, effectively improving its service life.