Properties of the Functionally Gradient Chromium-Niobium Carbide Coating Obtained by Thermo-Reactive Deposition Technique

Thermo-reactive deposition (TRD) salt bath Nb-Cr co-diffusion process was brought forward to prepare the functionally gradient chromium-niobium carbide coating. In TRD salt bath Nb-Cr co-diffusion treatment, T10 steel samples were delved into TRD salt. The samples were treated at 880°C for 3.5 h and then at 950°C for 2.5h. The obtained coatings were characterized by means of microstructure, microhardness, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and X-ray diffraction analysis (XRD). The cross-section hardness of the chromium-niobium carbide coating obtained on the surface of T10 steel samples transits smoothly. The coating was dense, smooth and compact. The thickness ratio of the niobium carbide layer (the outer layer) and the chromium carbide layer (the inner layer) was 4. The hardness of chromium-niobium carbide coating was about 2751HV0.05, which is between the single chromizing and single niobium. The results showed superior wear properties of the coated samples. The kinetics of chromium-niobium carbide coating was also studied.