The NbC-reinforced Fe-based laser clad coatings were obtained by ex-situ processing. The evolution behavior of ex-situ NbC was quantitatively researched and the microhardness and wear resistance of laser clad coatings were also investigated. The results show that the ex-situ NbC added in clad powder can decompose and re-precipitate during the laser clad process, which affects significantly the content and morphology of NbC. After the added NbC particles decompose during the heating process of laser beam, Nb and C atoms are released into the molten pool. However, a part of Nb atoms cannot react with C to form NbC, but dissolve into the coating matrix or form Fe₂Nb with Fe atoms, which decreases the content in NbC in clad coating. Moreover, Most of re-precipitated NbC phases belong to eutectic microstructure and exist in coating in the form of network or featherlike structure instead of the original particle shape. As heterogeneous nucleation core, the undecomposed NbC can promote the re-precipitation of new NbC phases. These new NbC can precipitate on the surface of undecomposed NbC particle, and then form the larger block and petaloid NbC phase with core. Both dissolved Nb atom and NbC precipitate can enhance the microhardness and wear resistance of coating, but the promotion role on the wear resistance is more obvious.

通过异位处理获得了NbC增强的Fe基激光熔覆涂层。定量研究了异位NbC的演变行为，并研究了激光熔覆涂层的显微硬度和耐磨性。结果表明，在激光熔覆过程中，包覆粉体中添加的异位NbC会发生分解和再沉淀，从而显着影响NbC的含量和形貌。在激光束加热过程中添加的NbC颗粒分解后，Nb和C原子释放到熔池中。但是，一部分Nb原子不能与C反应形成NbC，但会溶解到涂层基质中或形成Fe ₂Nb中含有铁原子，可降低覆层中NbC的含量。而且，大多数再沉淀的NbC相属于共晶微结构，并且以网状或羽毛状结构的形式而不是原始颗粒形状存在于涂层中。作为异质形核核心，未分解的NbC可以促进新NbC相的再沉淀。这些新的NbC可以沉淀在未分解的NbC颗粒表面，然后与核形成较大的块状和花瓣状NbC相。溶解的Nb原子和NbC沉淀物均可提高涂层的显微硬度和耐磨性，但对耐磨性的促进作用更为明显。