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 Ti3C2T
x
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.
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