The Tribological Behavior of Hybrid Graphene/Tungsten Disulfide Nanoparticle Coatings

Environmental concerns regarding the disposal of fluid lubricants have led to the application of green technologies to metalworking processes in the form of dry lubricants. These dry lubricants are typically applied as spray coatings that employ the use of nanoparticles. The possible use of graphene in the form of graphene/tungsten disulfide (G/WS2) nanoparticle spray coatings has been examined in this research. The investigation was performed through the use of ball-on-disk tests at ambient temperatures to ascertain the possible application of the aerosol spray coatings to the aluminum forming processes. The coatings proved to possess good adhesion to the Al-Mg alloy substrate. The nanoparticle spray coatings were tested at various graphene to WS2 concentrations and under varying loads. A low steady-state COF was noted for all graphene concentrations during sliding contact under all the loads examined. The durability of the coatings was observed to improve with increasing loads. The low COF was attributed to the formation of wear-induced transfer layers on the steel balls and tribolayers on the coated Al-Mg surfaces. The coating durability was related to the concentration of graphene within the nanoparticle spray coatings and the stability of the tribolayers during sliding contact. The results highlight that the G/WS2 nanoparticle spray coatings could be considered for aluminum metalworking processes.