The Fe-Co-B-Si-Nb alloy coatings were ckdded on the mild carbon steel surface by a high power diode laser. The phase aggregate and microstructure were analyzed by X-ray diffraction (XRD) and scanning electron microscope(SEM), respectively. The size of coatings was measured by optical microscope, and mi-crohardness was assessed using Vickers microhardness tester. The effect of laser power on coatings was studied. The results show that the coating dilution increases with increasing laser power when the other parameters are fixed. When the laser power was 1 050 W, an amorphous phase occurred in the coating. Granular crystals and a large grey area were observed in the middle of the coating. With increasing laser power, crystalline phases in the coating gradually increased and snow-like crystals were formed in the middle of the coating. The microstructures on the coating-substrate interface were plane crystal and columnar - dendrite crystals, which exhibited obvious extensive growth characteristics. The hardness of the coating decreased with increasing laser power.%采用高功率半导体激光器在低碳钢表面激光熔覆了Fe-Co-B-Si-Nb合金涂层.借助光学显微镜、X射线衍射仪(XRD)、扫描电子显微镜(SEM)以及致显维氏硬度计,探讨了激光功率对涂层稀释率、物相组成、微观组织及其显微硬度的影响.试验结果表明:在其它工艺参数一定的情况下,激光功率越大,涂层稀释率越大；激光功率为1050 W时,涂层中部的物相分析表现为具有非晶特征的漫散射峰,微观组织由颗粒状晶体和无组织形貌特征的灰色基底组成,随着激光功率的增大,涂层中部的晶化相衍射峰逐渐增多增强,微观组织中出现“雪花”状晶体；涂层和基材结合区的微观组织以具有外延生长特征的平面晶和柱状树枝晶为主;涂层的平均硬度随激光功率的增大而降低.
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