Improving the tribological properties of AISI M50 steel using Sns/Zno solid lubricants

Motivated by enhancing the tribological behavior of M50 steel (M), two nanoscale self-lubricants (SnS and/or ZnO) have been incorporated with M50 matrix to form two new matrix composites: M50 + 10%SnS (MS) and M50 + 10% SnS+10%ZnO (MSZ). The samples were fabricated using spark plasma sintering machine (SPS). The fabricated samples were tested against silicon nitride ceramics ball on a pin-on-disk tribometer under wide ranges of loads (3–12 N), sliding speeds (0.2–0.8 m/s), and temperatures (RT – 450 °C) to investigate the tribological behavior of the samples. FESEM, EDS, EPMA, XPS, and XRD tests were carried out to explore the morphology of worn surface and recognize the anti-wear and friction-reduction mechanisms of the samples. MSZ recorded the least friction (0.22) compared to MS (0.31) and M (0.58) under severe conditions (12 N load and 0.8 m/s sliding speed at temperature of 450 °C). The synergistic action between SnS and ZnO as well as produced lubricious oxides, molybdenites, and carbonates on interacting surfaces is the main reason to enhance the tribological characteristics of MSZ samples. •Effects of different loads on tribological behavior of M50 composites.•Effects of different sliding speeds on tribological behavior of M50 composites.•Effects of different temperatures on tribological behavior of M50 composites.•Effects of ZnO–SnS hybrid solid lubricants on tribological behavior of M50.•Major lubrication mechanisms of M50 composites are discussed in details.