Microstructure dependent mitigation of AFM plowing wear in WSe2 by water immersion

We have investigated how microstructure and environment affect the scratch response of WSe₂. Using diamond-coated AFM probes (2–10 µN), low- and high-polycrystalline and mineral WSe₂ were scratched in air and water. Scratch depth and width increased with load in all cases. In air, polycrystalline samples showed substantially greater damage than mineral WSe₂. In water, wear was significantly reduced for both polycrystalline materials, most notably for low-polycrystalline WSe₂. This was accompanied by lower and more stable friction during scratching, indicating reduced plowing. We attribute this to localized hydration at grain boundaries, pores, oxides, secondary phases and disordered regions, forming a lubricating interfacial layer that lowers shear resistance. Mineral WSe₂, with fewer such sites, shows minimal environmental dependence.