Investigation of the Structure and Properties of MoS2 Coatings Obtained by Electrospark Alloying

Electrospark coatings alloyed with MoS2 have been studied. The coatings were obtained by the following two strategies: the first consisted of pre-applying molybdenum disulfide to the treated surface and alloying with a molybdenum electrode (Mo + MoS2 coating); the second consisted of applying a paste with a sulfur content of 33.3% to the treated surface and alloying with a molybdenum electrode (Mo + S coating). The structure, phase composition, and tribological properties of the coatings were investigated. The coatings have a complex structure consisting of an upper soft layer, a hardened white layer, a diffusion zone, and a substrate. Element analysis and cross-sectional hardness changes indicated that element diffusion occurred at the coating/substrate interface. The phase composition of the coatings is represented by BCC and FCC solid solutions on Fe, and MoS2 is also detected. In Mo + S coatings, the molybdenum disulfide on the surface is about 8%; in Mo + MoS2 coatings, it is 27%-46%. The obtained coatings show very good tribological properties compared to molybdenum ESA coatings. The frictional forces and coefficients are reduced by a factor of 10 and 40, depending on the test conditions.