The effect of niobium carbide coating on wear behavior of grey cast iron via thermo-reactive diffusion process

Abstract

Wear is the limit for grey cast iron (GCI), which is utilized extensively in today’s industries. Coating the surface of a material can enhance its ability to withstand wear. In this study, thermo-reactive diffusion (TRD) process was used to coat the surface of grey cast iron with niobium carbide (NbC). The coatings were applied for 2, 4 and 6 hours at 950ºC and 1050ºC. The coated samples were subjected to metallographic examination to investigate the microstructure of the coating zone. For this purpose, optical microscopy examinations were carried out. Microhardness tests were carried out to assess the mechanical properties of the samples. The coated surfaces were analyzed using energy-dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Wear tests were carried out on the coated surfaces to measure the volumetric wear loss, the wear rate and the changes in the coefficient of friction. Coating thickness rose as furnace waiting time increased, according to optical microstructures of coated surfaces. The hardness of the coated surfaces increased with a longer coating duration. Depending on the duration and temperature of the coating process, the layer thickness ranged from 6 to 52 µm. The lowest microhardness and the highest microhardness values of the coatings were determined at 950ºC for 2 hours and at 950ºC for 6 hours, respectively. Compared to the uncoated samples, the coated samples had a 6-9 times higher hardness value. In the abrasion tests, the loss of wear volume increased with increase in load.