Morphological evolution of NbC particles at the interface of niobium-iron diffusion couple

To investigate the morphological evolution of the NbC phase, a niobium-cast iron diffusion couple was designed and fabricated. The two-dimensional (2D) and three-dimensional (3D) growth morphology of NbC particles were analysed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The morphological evolution mechanism of NbC particles was also discussed. The results reveal that from the interface of the Nb wire/NbC-Fe diffusion layer to the cast iron, as the thickness of the NbC-Fe diffusion layer increases, the morphology of NbC particles changed from the nearly spherical to truncated cube, then to a perfect cube. The evolution of particle morphology is mainly attributed to the change in the C/Nb ratio and the existence of Fe atoms affecting the relative growth rates of the {111} and {100} facets on a NbC crystal.