Mxene nanosheets as an emerging solid lubricant for machine elements ? Towards increased energy e fficiency and service life

Abstract

Solid lubricants like carbon-based materials, transition metal dichalcogenide compounds, polymers and soft metals, each with their specific merits and limitations, pursue the goal of reducing friction and wear between two rubbing surfaces under substantially dry conditions. Newly emerging early transition metal carbides and carbonitrides, such as Ti3C2Tx-nanosheets (MXenes), seem to be a promising candidate to be used as a solid lubricant due to their weakly bonded multilayer structure with self-lubricating character. For the first time, this paper aims at addressing the application of MXene nanosheets in higher loaded rolling-sliding contacts of machine elements by investigating their friction and wear behavior in thrust ball bearings under ambient conditions. Thereby, a reduction of the frictional torque by a factor of up to 3.2, an extension of the service life by about 2.1 times and a decrease of the linear cumulative wear rate by up to 2.9 compared to uncoated references have been verified. Thus, the Ti3C2Tx-coating already featured results comparable to reports on graphene, amorphous carbon coatings or advanced transition metal dichalcogenide, which demonstrates the tremendous potential of MXene nanosheets as outstanding, next-generation solid lubricant in machine elements.