Microstructure, friction and wear of NbC coatings on a Fe substrate fabricated via an in situ reaction

The microstructure, friction and wear of niobium carbide (NbC) coatings, which were prepared via an in situ reaction at 1085 degrees C for 10, 20 and 30 min on grey cast iron, were investigated. The coatings comprised NbC and alpha-Fe phases. The thickness of the coating increased, and a diffusion zone was found below it with a prolonged heating time. The diffusion of carbon from the substrate plays a dominant role in the formation of the coating. Carbon diffused towards a thin niobium plate to react with niobium to sustain the growth of the NbC coating. Furthermore, the mechanical and tribological performances of the coating that was treated at 1085 degrees C for 10 min were evaluated using the nanoindentation mode and the pin-on-disc sliding system, respectively. The microhardness was an average value of 22.4 GPa, which was 3.4 times that of the substrate. The compound coating exhibited a lower friction coefficient and wear rate compared with the substrate, indicating that it possesses a higher wear resistance and improves the tribological applications for the material surface. The surface morphologies of the worn samples revealed that the abrasive wear is dominant. (C) 2017 Elsevier B.V. All rights reserved.