posted on 2021-04-06, 16:36authored byPhilipp G. Grützmacher, Sebastian Suarez, Aura Tolosa, Carsten Gachot, Guichen Song, Bo Wang, Volker Presser, Frank Mücklich, Babak Anasori, Andreas Rosenkranz
Owing to MXenes’ tunable mechanical
properties induced by
their structural and chemical diversity, MXenes are believed to compete
with state-of-the-art 2D nanomaterials such as graphene regarding
their tribological performance. Their nanolaminate structure offers
weak interlayer interactions and an easy-to-shear ability to render
them excellent candidates for solid lubrication. However, the acting
friction and wear mechanisms are yet to be explored. To elucidate
these mechanisms, 100-nm-thick homogeneous multilayer Ti3C2Tx coatings are deposited
on technologically relevant stainless steel by electrospraying. Using
ball-on-disk tribometry (Si3N4 counterbody)
with acting contact pressures of about 300 MPa, their long-term friction
and wear performance under dry conditions are studied. MXene-coated
specimens demonstrate a 6-fold friction reduction and an ultralow
wear rate (4 × 10–9 mm3 N–1 m–1) over
100 000 sliding cycles, outperforming state-of-the-art 2D nanomaterials
by at least 200% regarding their wear life. High-resolution characterization
verified the formation of a beneficial tribolayer consisting of thermally/mechanically
degraded MXenes and amorphous/nanocrystalline iron oxides. The transfer
of this tribolayer to the counterbody transforms the initial steel/Si3N4 contact to tribolayer/tribolayer contact with
low shear resistance. MXene pileups at the wear track’s reversal
points continuously supply the tribological contact with fresh, lubricious
nanosheets, thus enabling an ultra-wear-resistant and low-friction
performance.