A New Insight into the Contact Sliding and Wear Resistance of 2D/Layered Materials and their Composites based on WS2 and Multilayer Graphene

While several coatings exist today to achieve tribological support on practical surfaces, the hunt for easily deployable yet tribological-efficient coatings still continues to fulfill the demand for commercial contact-sliding systems. Solution-based 2D/layered material coatings can be promising in this regard but many uncertainties remain to persist. Here we explored the tribological characteristics of solution-processed monolithic tungsten disulfide (WS2) and multilayer-graphene (mGR) coatings and simultaneously developed a new breed of WS2_mGR composite coating on stainless steel (SS) substrates. We discovered that monolithic WS2 coating (1mg/ml) is tribologically inefficient even at its higher concentration (up to 5mg/ml). The WS2_mGR composite coating demonstrated a remarkable reduction in friction and wear, with a 59% reduction in coefficient of friction (COF) compared to the Bare SS. Additionally, it demonstrated a 57% and 31% reduction in COF with respect to monolithic WS2 and mGR coatings, respectively, both prepared with the same concentration (1mg/ml). Further, we also discovered that at higher concentrations (5mg/ml) the monolithic mGR coating attains the lowest and most stable friction and high wear resistance over a longer period of time, even without the need for intermittent supply of lubricants during contact sliding.