针对42CrMo钢易发生磨损失效的问题,采用激光熔覆混合粉末(Co基粉、Nb粉和Cr3C2粉)在42CrMo钢表面成功制备了原位NbC颗粒增强复合涂层,分析了NbC含量对复合涂层微观结构、磨损行为以及NbC形态的影响。结果表明:当NbC的质量分数为0~15%时,涂层与基材的结合性能良好,涂层中没有明显的缺陷;当NbC的质量分数为20%时,涂层中出现了微裂纹;复合涂层的基体主要由ε-Co和γ-Co组成,强化相主要包括NbC、Cr23C6和Cr7C3;NbC颗粒的形成是通过溶解在熔池中的Nb原子和C原子以原位反应形成的;随着NbC含量增加,NbC的形态逐渐从四边形变为花瓣形,复合涂层的显微硬度和耐磨性明显增加,磨损形式主要是磨粒磨损和硬质相剥落磨损;当NbC的质量分数为10%时,涂层的显微硬度和耐磨性最佳,显微硬度和磨损速率分别为546.4 HV和0.020 g/min。

To solve the problem of wear failure of 42CrMo steel and meet its application requirements, in situ NbC-particle-reinforced composite coatings were prepared on a 42CrMo steel surface using laser cladding with a mixed powder (Co-based, Nb,and Cr3C2 powder). The effects of NbC content on the microstructure, wear behavior, and NbC morphology of the composite coatings were analyzed. The results show that when the mass fraction of NbC is 0--15%, the coating bonds well with the substrate and no obvious defects are observed in the coating. When the mass fraction of NbC reaches 20%, microcracks appear in the coating. The matrix of the composite coating primarily comprises ε-Co and γ-Co. The primary strengthening phases are NbC, Cr23C6, and Cr7C3. NbC particles are formed by the in-situ reaction of Nb and C atoms that are dissolved in the molten pool. With the increase of NbC content, the shape of the NbC particles gradually changes from quadrilateral to petaling. The microhardness and wear resistance of the composite coatings clearly increase, and the primary wear forms of the composite coatings are abrasive wear and hard-phase spalling wear. When the mass fraction of NbC is 10%, the microhardness and wear resistance of the coatings attain their maximal values of 546.4 HV and 0.020 g/min, respectively.