Enhanced Tribological Performance of Low-Friction Nanocomposite WSexSy/NP-W Coatings Prepared by Reactive PLD

Abstract

A novel laser-based method for producing nanocomposite coatings consisting of a tungsten sulfoselenide (WSexSy) matrix and W nanoparticles (NP-W) was developed. Pulsed laser ablation of WSe2 was carried out in H2S gas under appropriate laser fluence and reactive gas pressure. It was found that moderate sulfur doping (S/Se ~0.2–0.3) leads to significant improvement in the tribological properties of WSexSy/NP-W coatings at room temperature. Changes in the coatings during tribotesting depended on the load on the counter body. The lowest coefficient of friction (~0.02) with a high wear resistance was observed in a N2 environment at an increased load (5 N), resulting from certain structural and chemical changes in the coatings. A tribofilm with a layered atomic packing was observed in the surface layer of the coating. The incorporation of nanoparticles into the coating increased its hardness, which may have influenced the formation of the tribofilm. The initial matrix composition, which had a higher content of chalcogen atoms ((Se + S)/W~2.6–3.5), was altered in the tribofilm to a composition close to the stoichiometric one ((Se + S)/W~1.9). W nanoparticles were ground and retained under the tribofilm, which impacted the effective contact area with the counter body. Changes in the tribotesting conditions—lowering the temperature in a N2 environment—resulted in considerable deterioration of the tribological properties of these coatings. Only coating with a higher S content that was obtained at increased H2S pressure exhibited remarkable wear resistance and a low coefficient of friction, measuring 0.06, even under complicated conditions.

Editorial: Special Issue “Laser Synthesis and Processing of Nanostructured Materials”

“…Special Issue was focused on recent trends in the fabrication of functional nanostructures, nanomaterials and nanotextured surfaces using laser radiation. The resulting content of this Special Issue comprising 10 original papers reflects the diversity of the developing nanofabrication strategies that utilize pulsed laser radiation, including pulsed laser ablation in liquid (PLAL) for nanomaterial generation [ 1 , 2 , 3 , 4 ], pulsed laser deposition (PLD) of functional coatings [ 5 ], laser-induced forward transfer (LIFT) [ 6 ], laser sintering [ 7 ], pulsed laser surface nanotexturing [ 8 ] and direct laser writing in transparent media [ 9 , 10 ].…”

“…Importantly, the reported results bridge the gap between SERS-based bio-sensing and flexible electronics via inexpensive, scalable and environmentally friendly laser nanofabrication technology. Fominski et al reported the deposition of composite coatings made of a tungsten sulfoselenide (WSe x S y ) matrix embedding tungsten (W) nanoparticles through pulse laser ablation of WSe 2 carried out in gaseous H 2 S [ 5 ]. The PLD-fabricated coating demonstrated improved hardness and remarkable tribological characteristics even under multiple bending cycles and low temperature tests.…”