MXene and MXene/MoS2 Solid Lubricant Coatings in Journal Bearings

Abstract

To decrease humans’ negative environmental impact, it is crucial to decrease friction and wear in mechanical systems. For this purpose, two-dimensional (2D) nanomaterials, such as MXenes, can be used as solid lubricants in harsh environments. MXenes have been mainly studied under laboratory conditions; however, the tribological performance of coated mechanical parts has not yet been sufficiently researched. Therefore, this work aims at evaluating the tribological potential of MXene and hybrid MXene/MoS₂ coatings as solid lubricants in real journal bearings. Steel shafts were spray-coated with multilayer MXene Ti₃C₂T_x, MoS₂, and a mixture of these two nanoparticles (hybrid coating). Afterward, a multiple-bearing wear tribometer was used to test the coated shafts against standard bronze journal bearings as counter bodies. The tests were conducted under different atmospheric humidities under low contact pressure conditions. Wear and chemical analyses provided insights into the tribological performance of the 2D coatings and shed light on the chemical composition of the wear track and the resulting tribofilm. The results showed a lower coefficient of friction and increased wear resistance for MoS₂, Ti₃C₂T_x, and the hybrid coating compared to the uncoated reference materials, with MoS₂ as the best performer. Overall, a decrease in atmospheric humidity improved the tribological performance of the coatings. Based on the results of the chemical analysis, stable tribofilms were formed for MoS₂ and the hybrid coatings, whereas a full tribofilm for Ti₃C₂T_x was not achieved under the tested conditions.