激光熔覆NiCrBSi涂层的组织和耐磨性能

Microstructure and Wear Resistance of Laser-Cladding NiCrBSi Coating

采用TJ-HL-T5000型5kW横流CO2激光器,利用粉末预制法在45钢表面制备出NiCrBSi合金涂层,利用扫描电镜、能谱仪和X射线衍射仪、显微硬度计及M-200型环-块磨损试验机对涂层进行了微观组织分析和性能测试。结果表明,在优化工艺参数条件下,激光熔覆层与基体为冶金结合,内部组织致密,无裂纹和气孔等缺陷。熔覆层组织由树枝晶γ-Ni固溶体、共晶Ni3B、块状颗粒CrB和树枝晶Cr23C6等相组成,涂层显微硬度为(HV0.2)500～650,比基体的显微硬度(HV0.2)250提高2倍以上。激光熔覆层中由于存在颗粒强化和细晶强化等多种强化作用,因此显著提高了45钢的耐磨性能。

NiCrBSi coating was prepared on the surface of 45 steel with 5 kW TJ-HL-T5000 CO2 laser by powder metallurgy. The microstructure and properties of the cladding layer were characterized by SEM （scanning electron microscope）, EDX （energy dispersive X-ray）, XRD （X-ray diffraction）. The micro- hardness and wear resistance of the laser cladding layer were examined by microhardness meter and M- 200 ring-block wear tester. The results show that laser cladding layer with the good metallurgical bond- ing between the coating and substrate and dense, uniform, continuous and free of pores and cracks can be observed based on the optimized processing parameters. The microstructure of the cladding coating is mainly composed of dendrite γ-Ni,eutectic NiaB,bulky particles CrB and dendrite Cr23C6 particles. The microhardness of the cladding coating （HV0.2）500-650 is approximately 2 times than that of the substrate（HV0.2 ）250, which is attributed to particle strengthening and grain-refining strengthening effects, greatly improving wear resistance of 45 steel.