目的 提高Ti-6Al-4V钛合金的表面硬度和耐磨性，解决失效问题。方法 利用半导体激光器在纯氮气氛下对Ti-6Al-4V钛合金表面进行激光渗氮处理，研究激光功率和扫描速度耦合作用下不同热输入对渗氮层质量的影响。分别采用X射线衍射仪、扫描电子显微镜、X射线能谱仪，对渗氮层的物相组成、截面微观组织以及元素分布进行表征，采用显微维氏硬度仪测量渗氮层截面硬度分布。结果 不同热输入下Ti-6Al-4V钛合金氮化区域均生成TiN相，且含量随热输入的增大而增加，渗氮层厚度随热输入的增大呈近似直线增长。渗氮层组织由表及里依次由连续的TiN薄层、柱状晶、树枝晶和针状晶组成，使渗氮层内硬度随层厚的增加呈下降趋势，随热输入的增大，树枝晶中粗枝晶的数量增加，渗氮层硬度也随之增加。然而当热输入较高（320 J/mm）时，渗氮层内产生大量的裂纹。结论 利用激光气体氮化技术，控制热输入为210~275 J/mm时，在Ti-6Al-4V钛合金表面制备渗氮层，其表面成形良好、无裂纹，厚度约为413~517 μm，近表层硬度较基材提高2.5倍以上。

The work aims to enhance the surface hardness and wear resistance of Ti-6Al-4V alloy and solve the failure problem. Laser nitriding treatment was conducted toTi-6Al-4V alloy in pure nitrogen atmosphere by diode laser and the effect of different heat inputs on the quality of nitriding layer under the coupling of laser power and scanning speed was studied. The phase composition, cross-sectional micro-structure and element distribution of nitriding layer were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and energy dispersive spectrometer (EDS), respectively. The hardness distribution of nitriding layer was measured by microVickers hardness tester. TiN phase was formed in nitriding area of Ti-6Al-4V titanium alloy under different heat inputs, and the volume fraction of TiN phase increased with the increasing heat input. Meanwhile, the thickness of the nitriding layer increased approximately linearly with the increasing heat input. The nitriding layer consisted of continuous TiN layer, columnar crystals, needle crystals and dendrites in turn from surface to inside, and the hardness decreased with the increase of nitriding layer thickness. With the increase of heat input, the number of coarse dendrites and the thickness of nitriding layer increased. However, when the heat input was up to 320 J/mm, the cracks were found in the nitriding layer. A crack-free nitrided layer with a good surface and thickness of about 413~517 μm can be prepared on the Ti-6Al-4V alloy surface by laser gas nitrided technology through regulating the heat input to 210~275 J/mm, and the near surface hardness is over 2.5 times than that of the substrate.