Investigation of the wear and corrosion behavior of cr-v-c coatings formed on the surface of spheroidal graphite cast iron by thermoreactive diffusion technique

In this study, chrome vanadium carbide composite coating was produced on the surface of ductile iron GGG-80 by thermoreactive diffusion. The TRD process was carried out at temperatures of 900, 1000, and 1100 °C for 1 h using nano-sized Fe-V and Fe-Cr powders. The coatings were characterized by X-ray diffractometry (XRD), 2D profilometry, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), microhardness measurements, Daimler-Benz Rockwell-C adhesion test, nanoindentation, electrochemical corrosion tests and wear tests. Corrosion tests were performed electrochemically at room temperature in 3.5% NaCl, 5% H2SO4 and 5% HNO3 solutions. The wear tests were performed on untreated and coated samples using a ball-on-disc type wear tester under 10 N load at four different temperatures (25 °C, 250 °C, 500 °C and 750 °C) against a 6-mm WC ball in air. Metallographic investigations revealed that the graphite nodules were gradually dissolved and a coating with a thickness of 12-36 μm, hardness of 2461-31200 HV0.05, and elastic modulus of 198-233 GPa was obtained. The dissolution of graphite nodules and the growth of composite carbide coatings on the surface resulted in improved corrosion resistance in NaCl, H2SO4 and HNO3 compared to untreated GGG-80. In addition, with the increase in the hardness and modulus of elasticity in the composite coatings, higher wear resistance was obtained from room temperature to 750 °C. Increase in coating temperature, resulted in increased coating thicknesses and improved mechanical properties and a decrease in surface roughness values, and optimal wear and corrosion resistance values were obtained in the sample coated at 1100 °C for 1 hour.