Gokay Adabasi1,Aditya Deshpande2,Koichi Tanaka2,Joshua Ancheta1,Emmanuel Maldonado1,Mehmet Ozdogan1,Mehmet Baykara1,Suneel Kodambaka2,3
University of California, Merced1,University of California, Los Angeles2,Virginia Tech3
Gokay Adabasi1,Aditya Deshpande2,Koichi Tanaka2,Joshua Ancheta1,Emmanuel Maldonado1,Mehmet Ozdogan1,Mehmet Baykara1,Suneel Kodambaka2,3
University of California, Merced1,University of California, Los Angeles2,Virginia Tech3
Recent years saw accelerating interest from the scientific community in high entropy alloys (HEA), mainly due to their favorable mechanical properties and resistance to environmental stressors. In principle, their outstanding wear and corrosion resistance make them great candidates for coatings in mechanical systems. On the other hand, the question of whether HEA thin films will also act as solid lubricants, i.e. reduce friction at the interface of mechanical components in relative motion, remains open.<br/><br/>In order to find answers to this critical question, we performed nanoscale friction measurements on sputter-deposited HEA-sulfide ((VNbTaMoW)S<sub>2</sub>) thin films via atomic force microscopy (AFM). Results reveal (i) the influence of deposition time on film morphology and (ii) the presence of isolated areas of low friction on film surfaces. Taking one step further, we compared the nanoscale friction results obtained on the HEA-sulfide thin films with those on sputter-deposited molybdenum disulfide (MoS<sub>2</sub>), a widely-used material for solid lubrication. Friction values obtained on both types of films are on the same order. Finally, variable temperature X-ray diffraction (XRD), performed up to 800 °C, reveals that (VNbTaMoW)S<sub>2</sub> films exhibit improved oxidation resistance when compared with MoS<sub>2</sub> films. Combined, the results presented here demonstrate that HEA-sulfide thin films exhibit remarkable potential as environmentally-resistant solid lubricant coatings.