Production and characterization of niobium carbide coatings produced on tool steels by thermoreactive deposition/diffusion

Abstract

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.

Improvement of Corrosion Resistance for Gray Cast Iron in Palm Biodiesel Application Using Thermoreactive Diffusion Niobium Carbide (NbC) Coating

“…Figure 10 shows the Nyquist diagrams obtained from the electrochemical impedance test performed on the niobium carbide coating submerged in biodiesel at a temperature of 291 ± 2 K with immersion times of 1 h, 24 h, 48 h, and 144 h. It was observed that the diagram was composed of two overlapping semicircles, suggesting the presence of two constant phase elements corresponding to two electrolyte-electrode interphases. The first, at high frequencies and a larger radius, is usually associated with the resistive-capacitive behavior of the coating; and the second time constant was related to the electrolyte-substrate interface due to the pores in the coating [24,25]. The polarization resistance decreased from 1.48 × 10 10 Ω to 8.95 × 10 9 Ω with an increase in the immersion time.…”

“…The presence of additional peaks related to NbO, NbO 2 , and Nb 2 O 5 was observed. The diffractograms showed that the two surfaces interacted with the biodiesel and that different species of oxides appeared, which were produced during the corrosion process [24]. The X-ray patterns made by the iron smelter before and after the biodiesel corrosion process are shown in Figure 8.…”

“…The presence of additional peaks related to NbO, NbO2, and Nb2O5 was observed. The diffractograms showed that the two surfaces interacted with the biodiesel and that different species of oxides appeared, which were produced during the corrosion process [24]. Figure 10 shows the Nyquist diagrams obtained from the electrochemical impedance test performed on the niobium carbide coating submerged in biodiesel at a temperature of 291 ± 2 K with immersion times of 1 h, 24 h, 48 h, and 144 h. It was observed that the diagram was composed of two overlapping semicircles, suggesting the presence of two constant phase elements corresponding to two electrolyte-electrode interphases.…”

Properties and in-service performance of components reated with thermo reactive deposition/diffusion

“…Crystallographic planes are observed in orientations (111), (200) and (311), with crystal cubic system (Fm3m) and space group 225. As the layers are formed as a consequence of the direct combination of carbon in the steel with niobium dissolved in the bath, the presence of alloying elements in the steel does not have effect on the composition of the coatings [19]. Figure 2 shows SEM micrographs of the crosssection of the coatings produced on the tools.…”

An Overview on the Corrosion Behavior of Steels Processed by Severe Plastic Deformation

“…In many applications, tool steels are coated with transition metal carbides to improve corrosion resistance. Some authors report the improvement in the corrosion resistance of AISI D2 (111,112,113,114,115,116,117) and AISI H13 115) tool steel with the production of a layer of chromium niobium carbide on the steel surface, and other works have reported that for tool steels the corrosion behavior could be more influenced by its phase composition that the nanocrystalline structure (118) .…”