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Chromium carbide, vanadium carbide, and chromium–vanadium mixture coatings were deposited on AISI D2 steel via the thermo-reactive deposition/diffusion (TRD) technique. The carbides were obtained from a salt bath composed of molten borax, ferro-chrome, ferro-vanadium, and aluminum at 1020 °C for 4 h. Analysis of the morphology and microstructure of the coatings was done via scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The hardness of the coatings was evaluated using nano-indentation, and the friction coefficient was determined via pin-on-disk (POD) testing. The electrochemical behavior was studied through potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS). The XRD results show evidence of the presence of V8C7 in the vanadium carbide coating and Cr23C6 and Cr7C3 in the chromium carbide coating. The hardness value for the vanadium–chromium carbide coating was 23 GPa, which was higher than the 6.70 ± 0.28 GPa for the uncoated steel. The wear and corrosion resistance obtained was higher for the niobium–chromium carbide coating, due to the nature of the ceramic carbide produced.

RESUMENEn este trabajo se depositaron recubrimientos de carburo de niobio sobre aceros AISI M2, H13 y D2, utilizando la técnica de deposición por difusión termorreactiva. Los carburos se obtuvieron usando baños de sales compuestos por bórax fundido, ferroniobio, ferrovanadio y aluminio a una temperatura de 1.020 °C durante 4 horas. La presencia de los recubrimientos fue observada por microscopia electrónica de barrido. Las fases fueron determinadas usando difracción de rayos X, y se utilizó microdureza para determinar la dureza. El comportamiento electroquímico fue estudiado mediante curvas de polarización potenciodinámica para determinar la densidad de corriente de corrosión, y espectroscopia de impedancia electroquímica para determinar la resistencia a la polarización. Los resultados fueron comparados con las propiedades del sustrato sin recubrimiento y en general se observó mayor dureza y mejor resistencia a la corrosión en los recubrimientos producidos.Palabras clave: Difusión, carburos de niobio, impedancia, aceros para herramientas, corrosión. ABSTRACTIn this work, niobium carbide coatings were deposited on AISI M2, H13, and D2 tool steels by thermoreactive deposition/diffusion. The carbides were obtained using salt baths composed of molten borax, aluminum, and ferroniobium at a temperature of 1020 °C for 4 hours. The coatings were observed via scanning electron microscopy. The phases were determined using X-ray diffraction, and Vickers indentation was used to determine the hardness. The electrochemical behavior was studied via potentiodynamic polarization curves to determine the rate of corrosion and electrochemical impedance spectroscopy was used to determine the resistance to polarization. The results were compared with the properties of the substrate without a coating, and in general, greater hardness and better corrosion resistance were observed with the coatings.

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