目的 采用激光熔覆法在45#钢表面制备耐磨耐蚀的Mo2NiB2-Cr7C3复合陶瓷熔覆层, 并研究制备工艺对组织结构与性能的影响。方法 采用3 mm/s与4 mm/s的激光扫描速率及添加Cr7C3颗粒的工艺，激光熔覆制备Mo2NiB2-Cr7C3熔覆层。利用扫描电镜、X射线能谱仪、X 射线衍射仪对熔覆层的组织结构、元素分布与物相组成进行分析。利用维氏显微硬度计、摩擦磨损仪与电化学工作站对熔覆层的硬度、摩擦性能与腐蚀性能进行分析。结果 Mo2NiB2-Cr7C3复合陶瓷熔覆层与45#钢基材间存在熔合过渡区，形成良好的冶金结合。熔覆层物相主要由 Mo2NiB2、Cr7C3、{FeNi}合金相组成，其中 Mo2NiB2相与Cr7C3相在熔覆层中间位置处聚集，3 mm/s扫描速率增加了{FeNi}相的含量。熔覆层的显微硬度由表及里先增后减，最高值可达1300HV0.1以上，可提高45#钢的硬度(220HV0.1)6倍。相较于45#钢，熔覆层具有更低的摩擦因数、磨损量与更优的耐腐蚀性能，其中4 mm/s制备的Mo2NiB2-Cr7C3硬度最高，耐磨性能最优(平均摩擦因数为0.66，磨痕深度为8.6 μm)，耐腐蚀性能最好(腐蚀电流比45#钢低1个数量级)。结论 较高的扫描速率(4 mm/s)与Cr7C3颗粒的添加可有效提高Mo2NiB2-Cr7C3熔覆层的机械与耐腐蚀性能，可用于45#钢的表面改性。

A wear-resistant and corrosion-resistant Mo2NiB2-Cr7C3 composite coatings were prepared on the substrate of 45# steel by laser cladding. The effects of laser cladding parameters including scanning rates of 3 and 4 mm/s and the addition of Cr7C3 particles on the microstructure and properties of the cladding coatings were investigated. The SEM, EDS, XRD, micro-hardness tester, friction and wear tester and electrochemical workstation were used to character the microstructure, composition and properties of the cladding coatings. Results showed that a fusion transition zone was appeared between the cladding coating and the substrate, consequently leading to a good metallurgical bond. The main phases in cladding coating were Mo2NiB2, Cr7C3 and {FeNi} phases. The Mo2NiB2 and Cr7C3 phases preferred gathering in the middle of the cladding coatings. And the laser scan rate of 3 mm/s brought in the increased content of {FeNi} phase in the coating. From top layer to bottom layer of the coating, the micro-hardness firstly increased and then decreased, in which the highest micro-hardness could reach more than 1300HV0.1, 6 times higher than that of 45# steel (220HV0.1). Compared with 45# steel, the cladding coatings possessed the lower friction coefficient and wear loss and better corrosion resistance. Especially, the Mo2NiB2-Cr7C3 coating prepared at 4 mm/s possessed the highest micro-hardness, the best wear resistance (friction coefficient of 0.66, scratch depth of 8.6 μm) and the best corrosion resistance (Jcorr is one order of magnitude lower than 45# steel). Therefore, the high laser scanning rate (4 mm/s) and the addition of Cr7C3 particles could effectively enhance the mechanical properties and corrosion resistance of the Mo2NiB2-Cr7C3 coatings, consequently fulfilled the surface modification of 45# steel.