The paper presents the results of using plasma electrolytic treatment for sulfiding of carbon tool steel. The steel surface was saturated with sulfur in an electrolyte based on ammonium sulfate and dimethylsulfoxide at 550°C. Before and after diffusion saturation, various types of heat treatment were applied: quenching from 780°C after sulfiding, tempering before and after saturation from 780°C. An analysis of the structural and phase changes in the sulfided surface revealed the formation of FeS, Fe3S4, and Fe2S3 iron sulfides, the amount of which is determined by the use of heat treatment before and after saturation, and the formation of martensite after quenching and Fe3O4 oxides as a result of high-temperature oxidation. Tribological tests were conducted in the dry friction mode using the “shaft-bushing” scheme under a load of 10 N and the sliding speed of the sample on the counter body of 1.555 m/s per 1000 m of the friction path. An increase in weight wear after plasma electrolytic sulfiding with quenching was found to be 17 times greater than that of an untreated sample, 13 times greater than that of water- and oil-quenched samples, and 14 times greater than that of tempered samples. The wear resistance of sulfided steel was determined by the structure of the deformation zone material during friction, containing iron sulfides.
Mukhacheva et al. (Sun,) studied this question.