Evaluation of Tribological Properties of Hard Coatings Obtained on Steel C45 by Electro-Spark Alloying

Abstract

It was shown that under dry contact conditions, under normal load of to 2 MPa, all coatings demonstrated a significant increase in wear resistance compared to that of the substrate. However, among them, the Mo coating showed the highest wear resistance: ~20 times higher than that of the uncoated steel. That was caused not only by the Mo high microhardness and the lowest initial roughness, but also by the structure of this coating. Meanwhile, the Ti + SiC samples displayed the highest microhardness among investigated coatings. A correlation was established between the microhardness of the coating and the friction coefficient: the larger the microhardness of the coating, the higher is the coefficient of friction. An X-ray analysis of the coatings obtained by ESA on steel with compositions (Ti + Al + C), (Ti + AlN) and (Ti + SiC) revealed phases of titanium carbide, titanium nitride, intermetallic compound AlFe3, and small amounts of aluminum nitride, silicon dioxide and titanium dioxide. This could explain the high microhardness (from 6.8 up to 13.8 GPa) of the obtained coatings.