The excellent properties of metallic glass (MG) films make them perfect candidates for the use in miniature systems and tools. However, their high coefficients of friction (COFs) and poor wear resistance considerably limit their long-term performance in nanoscale contact. We report the fabrication of a MG/graphene multilayer by the repeated deposition of Cu₅₀Zr₅₀ MG with alternating layers of graphene. The microstructure of the multilayer was characterized by the transmission electron microscopy (TEM). Its mechanical and nanotribological properties were studied by nanoindentation and nanoscratch tests, respectively. A molecular dynamics (MD) simulation revealed that the addition of graphene endowed the MG with superelastic recovery, which reduced friction during nanoscratching. In comparison with the monolithic MG film, the multilayer exhibited improved wear resistance and a low COF in repeated nanowear tests owing to the enhanced mechanical properties and lubricating effect caused by the graphene layer. This work is expected to motivate the design of other novel MG films with excellent nanowear properties for engineering applications.

As engineering equipment is applied in a harsh environment with a heavy load, cyclic stress, and a wide range of temperatures, the reliability of the equipment becomes a challenge, especially when wear contact is involved. Hence, the design and exploitation of an advanced alloy surface may hold the key to control and minimize friction and wear in the transmission system for safety-critical applications. High entropy alloys (HEAs) or multi-component alloys have been proved to have outstanding mechanical properties, corrosion resistance, and high-temperature oxidation resistance with potential use as wear resistance and friction reduction coatings. In this paper, the properties and development status of HEAs coating systems for tribological applications were reviewed to gain a better understanding of their advantages and limitations obtained by different preparation methods. Specifically, focus was paid to magnetron sputtering, laser cladding, and thermal spraying since these three deposition methods were more widely used in wear-resistant and friction-reducing coatings. Building upon this, the correlation between composition, mechanical properties, and friction as well as wear characteristics of these coatings are summarized. Finally, the key problems to be solved to move the field forward and the future trend of tribology application for HEA coatings are outlined.

The biological materials evolved in nature generally exhibit interpenetrating network structures, which may offer useful inspiration for the architectural design of wear-resistant composites. Here, a strategy for designing self-lubricating medium entropy alloy (MEA) composites with high strength and excellent anti-wear performance was proposed through quasi-continuously networked in-situ carbides and graphene nanosheets. The discontinuous coating of graphene on the MEA powder surface inhibits continuous metallurgy bonding of the MEA powders during sintering, generating the typical quasi-continuously networked architecture. A good combination of mechanical properties with high fracture strength over 2 GPa and large compressive plasticity over 30% benefits from metallurgy bonding that prevents crack initiation and extension. The wear rate of an order of 10^-6 m³N^-1m^-1 ascribing to an amorphous-crystalline nanocomposite surface, tribo-film induced by graphene, as well as the gradient worn subsurface during friction was achieved by the MEA composite, which is an order of magnitude lower than the unreinforced MEA matrix.