Transition Metal Dichalcogenides (TMD) is a family of materials known for its layered structure, resulting in a strong anisotropy of the mechanical and electrical properties. Molybdenum disulphide, MoS2, and tungsten disulphide, WS2 are known for its lubricious properties. The use of these materials as a solid lubricant can be most advantageous in relation with conventional liquid lubrication. However there are features that are detrimental for its application, such as low adhesion to the substrate, poor mechanical properties, and low load bearing capacity, also the performance is influenced by the environmental conditions. From the different ways that these materials can be applied on the surface of the parts, magnetron sputtering is one of the most used process. In ICEMS, now CEMMPRE at University of Coimbra, the research on TMD coatings started more than 20 years ago [1]. The developments initiated with the WS2 alloyed with C or N in a reactive process by RF Magnetron Sputtering, figure 1 shows the difference of the pure and alloyed coating structure. The goal of the research was to improve the tribological performance by decreasing the coefficient of friction and increasing the wear resistance in a wide range of conditions. The structure, morphology and mechanical properties were evaluated with great detail and related to the tribological performance. The research is still on going and more than 25 papers were already published.

The aim of the research is obtain coatings with low wear and friction over a wide range of conditions. Thus, after find out the main characteristics to have a good tribological performance, the optimization of the process to a semi-industrial deposition chamber was accomplish [2]. The research is still being developed with the study on new coating designs, surface treatments, other TMD, and different alloying elements [3].

[1] A. Nossa; A. Cavaleiro Surf. Coating. Technol, 2001, 142, 984-991.

[2] T. Vuchkov; M. Evaristo; T.B. Yaqub; A. Cavaleiro Surf. Coating. Technol, 2020, 386, 984-991.

[3] T. Vuchkov; M. Evaristo; A. Carvalho; A. Cavaleiro Tribology International, 2022, 174, 107758