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A new M50 matrix composite sintered with a hybrid Sns/Zno nanoscale solid lubricants: an experimental investigation

To improve the tribological behavior of AISI M50 steel (M), ZnO and SnS nanoscale solid lubricants were added to M50 matrix and sintered using spark plasma sintering technique (SPS) to fabricate two self-lubricating composites: M50 + SnS (MS) and M50 + ZnO + SnS (MZS). Friction tests were performed on a pin-on-disk tribometer using a silicon nitride ceramic under different loads (3, 6, 9, and 12 N) and different speeds (0.2, 0.4, 0.6, and 0.8 m s−1) to figure out the effects of theses parameters on the tribological performance of the developed composites. FESEM, EPMA, EDS, and XRD tests were performed to analyze the worn surface morphology and to understand the friction-reduction and anti-wear mechanisms of the developed composites. Wear and dry friction properties of MS and MZS were found to be superior at high loads and sliding speeds. Applied loads and sliding speeds change widely the wear mechanisms of M50 steel. Excellent tribological characteristics of the developed composites were attributed to the synergistic effects of ZnO-SnS and the created lubricious oxides, carbonates, and molybdenites on wear track surfaces.