Laser remelting can be used not only to improve the metal surface structure, but also to repair metal surface defects. 34CrNiMo6 belongs to European standard high strength alloy structural steel. It has been widely used in the manufacture of large-size shaft parts which are prone to defects such as cracks and wear during service. This study proposed a repair method for these defects by laser remelting the filled block and then performed heat treatment. The microstructure, m9icrohardness and tensile strength of the repaired sample and heat-treated sample were analyzed using scanning electron microscope (SEM), Vickers hardness tester and universal tensile tester. The final results showed that the metallurgical bonding between the substrate and the filler was good. The microstructure of repaired sample could be divided into three regions: I, II, and III. The main microstructure in region I and II was tempered martensite, and in region III was bainite and martensite. Different regions of repaired sample presented uneven hardness distribution, and the fracture mode was quasi-cleavage fracture. However, after heat treatment, the microstructure of the sample was tempered martensite. Its hardness became uniform, and the fracture mode of the heat-treated sample was ductile fracture. The average hardness value of the heat-treated sample was 296.4HV_0.2, which was slightly higher than the substrate. The tensile strength value of the heat-treated sample reached 972.91MPa, which was about 99.3% of substrate, and its elongation δ was 14.25%. Overall, the mechanical properties were close to those of the forging.

激光重熔不仅可用于改善金属表面结构，而且可用于修复金属表面缺陷。34CrNiMo6属于欧洲标准的高强度合金结构钢。它已被广泛用于大型轴零件的制造中，这些零件在使用过程中容易产生裂纹和磨损等缺陷。这项研究提出了一种通过激光重熔填充的块然后进行热处理来修复这些缺陷的方法。使用扫描电子显微镜（SEM），维氏硬度计和万能拉伸测试仪分析修复后样品和热处理后样品的显微组织，耐硬度和拉伸强度。最终结果表明，基材与填料之间的冶金结合良好。修复后的样品的微观结构可分为三个区域：I，II，和III。I和II区的主要显微组织为回火马氏体，III区为贝氏体和马氏体。修复样品的不同区域呈现出不均匀的硬度分布，断裂模式为准劈裂断裂。但是，热处理后，样品的显微组织为回火马氏体。其硬度变得均匀，并且热处理样品的断裂模式为韧性断裂。热处理后的样品的平均硬度值为296.4HV 其硬度变得均匀，并且热处理样品的断裂模式为韧性断裂。热处理后的样品的平均硬度值为296.4HV 其硬度变得均匀，并且热处理样品的断裂模式为韧性断裂。热处理后的样品的平均硬度值为296.4HV_0.2，略高于基材。热处理后的样品的抗拉强度值达到972.91MPa，约为基材的99.3％，伸长率δ为14.25％。总体而言，机械性能接近于锻件。