采用Nb:YAG激光器对高碳高合金钢Cr12进行了表面熔凝处理试验,分析了激光加工参数对熔凝单元体宽度的影响,采用光学显微镜、扫描电镜以及能谱仪分析了激光熔凝处理后Cr12钢单元体的微观组织和化学成分分布,测量了不同激光加工参数下熔凝单元体宽度,并用显微硬度计测试不同区域的微观硬度。结果表明:激光熔凝处理后得到熔凝区、热影响区和基体三层组织。熔凝区组织为极细的等轴晶和柱状晶,消除了夹杂相,合金元素基本均匀分布。热影响区的显微硬度较基体显著提高,熔凝单元体宽度随激光参数的变化呈一定规律性变化,其中离焦量对单元体宽度影响最大。 The effect of laser processing parameters on the width of the fused unit was analyzed by using Nb: YAG laser on the surface of the high carbon high alloy steel Cr12. The laser melting process was analyzed by optical microscope, scanning electron microscope and energy dispersive spectrometer After Cr12 steel unit body microstructure and chemical composition distribution, measured under different laser processing parameters of the melting unit body width, and with a microhardness tester for testing different regions of the microhardness. The results show that three layers of microstructure, heat affected zone and matrix are obtained after laser melting treatment. Melting zone organization for the fine equiaxed and columnar crystals, eliminating the inclusion phase, the basic uniform distribution of alloying elements. The microhardness of the heat affected zone is significantly higher than that of the matrix. The width of the fused unit varies with the laser parameters, and the defocus amount has the greatest influence on the unit width.