Electrospark deposition of Fe–Cr–Cu coatings on St3 steel

Abstract

It is well-known that chromium in metallic compositions forms dense passivating films that slow down corrosion. The new Fe–Cr–Cu coating was applied on St3 steel through electrospark deposition in an anode mixture consisting of copper and titanium granules, with the addition of chromium powder ranging from 4.85 to 13.26 wt. %. The weight gain of the cathode increased nearly twofold with the addition of chromium powder to the anode mixture. The structure of the coatings was analyzed through X-ray phase analysis, scanning electron microscopy, and energy dispersive spectrometry. The phase composition of the coatings consists of ferrochrome and copper. It is demonstrated that the proposed method of electrospark processing allows for the creation of Fe–Cr–Cu coatings with an average chromium concentration ranging from 55 to 83 at. %. The average copper content in the prepared coatings varied from 5 to 16 at. %. The highest concentration of chromium was observed in the coating prepared with the addition of 13.26 wt. % Cr to the anodic mixture. The corrosion behavior of the coatings was investigated using potentiodynamic polarization and impedance spectroscopy in a 3.5 % NaCl solution. Polarization tests have shown that applying Fe–Cr–Cu coatings to St3 steel can increase its corrosion potential by 12 to 19 % and reduce the corrosion current by 1.5 to 3.4 times. The microhardness of the coating surface ranged from 3.08 to 4.37 GPa, and the coefficient of friction ranged from 0.75 to 0.91. The maximum hardness and the lowest coefficient of friction were observed in the coating with the highest chromium content. It has been demonstrated that Fe–Cr–Cu coatings can enhance the wear resistance of the surface of St3 steel by 1.5 to 3.8 times.