Diamond is widely acknowledged as the hardest naturally
occurring
material. Nevertheless, when exposed to friction against ferrous metals,
it is prone to graphitization or amorphization, which limits the utilization
of its extremely high hardness and wear resistance. These issues have
persisted for decades without an effective solution. Here, we report
that a covalently bonded heterostructure with mixed-dimensional carbons
as a high-performance solid lubricant could effectively reduce diamond
surface friction and mechanochemical wear with excellent load capacity
and durability. When subjected to dry friction and heavy loads (20–150
N), the heterostructure exhibited a notable improvement over pristine
diamond with reduced friction coefficients and relative wear rates
by 22–45 and 67–91%, respectively. Especially under
a 20 N load, the relative wear rate was an order of magnitude lower
than that of pristine diamond. Additionally, experiments and molecular
dynamics simulations revealed that the heterostructure integrated
the outstanding properties of diamond (three-dimensional (3D)), nanographite
(3D), and graphene (two-dimensional (2D)), resulting in improved lubrication
and antiwear performance that could not be achieved by the individual
carbon materials. The findings in this work will be beneficial to
overcome the ferrous metal forbidden zone of diamond and are expected
to expand the applications of engineered diamond surfaces and graphite/graphene
in tribology, mechanics, and electronic fields.