Investigation of tribological and physical behavior of sulfide film produced by DC -regime plasma electrolysis

Abstract

Abstract Creating a layer of solid lubricant on the steel surface is one of the measures of protection against harsh conditions to which service parts are commonly subjected. This research assessed the feasibility of creating a layer of solid lubricant using the plasma electrolysis method. Sodium sulfate and sodium thiosulfate were used as sources of sulfur required for the process. SEM results showed that the plasma electrolysis process used in this study led to formation of a porous layer composed of FeS and FeS 2 phases on the surface of St12 steel. The results indicated that subjecting the surface to 10 min of plasma electrolysis process with 10% sodium thiosulfate as electrolyte is the best method for forming a continuous layer of sulfide on the steel surface. Other tested durations, compositions, and concentrations resulted in inadequate generation of layers or increased formation of FeS 2 instead of FeS, which was unfavorable. The results of the wear test showed that layers created by this method decreased the friction coefficient by up to 40%.