Transition metal dichalcogenide (TMD) coatings, such as molybdenum disulfide and tungsten diselenide, have attracted enormous scientific and industrial interest due to their outstanding friction, wear and lubrication properties and exhibition of unusual electrical, optical, and mechanical properties. The application of these coatings can be seen in various fields, including electronics, sensing, and energy storage applications. However, TMD-lubricity degradation caused by environmental molecules has continued to be an issue, resulting in a need for more durable coatings.
Dr. Ali Erdemir, professor in the J. Mike Walker ‘66 Department of Mechanical Engineering at Texas A&M University and Halliburton Chair, and his collaborators recently developed an improved powder coating by converting selenium nanopowders into lubricious molybdenum and tungsten selenides that will enable the reduction of friction by solid-state reactions under sliding conditions. In their method, they can sprinkle selenium powder onto the moving mechanical surfaces, turning them into an in-operando formation of a low-friction and wear reaction layer.
This research was published in Advanced Materials.
These findings come from a collaborative effort led by Drs. Philipp G. Grützmacher and Carsten Gachot from the Institute for Engineering Design and Product Development, Tribology Research Division, Dr. TU Wien, Vienna, Austria, Dr. Maria Clelia Righi from the Department of Physics and Astronomy, Alma Mater Studiorum, University of Bologna, Italy and other researchers from Austrian Excellence Center for Tribology Research, Austria.
This idea, which is radically different from previous observations, can lead to new technological applications due to the advantages that it brings.
“This idea, which is radically different from previous observations, can lead to new technological applications due to the advantages that it brings,” said Erdemir. “The use of solid powders of the right kinds of ingredients prevents the degradation of the lubrication properties by the adverse interaction with air humidity.”
In this case, the research team hypothesized that using a combination of powders, including molybdenum, tungsten, and selenium, could trigger a solid-state tribochemistry, leading to ultra-low friction and wear. This type of coating is the first of its kind.
“Our hypothesis proved to be correct, and our ab initio molecular dynamics simulation supported our hypothesis in a very powerful manner, altogether leading to a new discovery,” said Erdemir.
Additionally, tribological contacts can be easily replenished by feeding nanopowders right into the specific or critical contact points of moving mechanical systems, making them more cost-effective and environmentally friendly. It can also be applied at high-temperature conditions or the nanoscale.
In the future, they hope this research will set new trends for further development of the coatings that will lead to the industrial and practical implementation of their discovery.
Future efforts related to this work may involve more application-oriented studies to better understand the real engineering potentials of such layers resulting from sprinkling selenium and other powders onto moving surfaces.