Friction and wear control via hybrid 2D materials

Hybrid materials, as a consequence of the synergistic effect, enormously tune the electrical, optical, optoelectronic, and other functional properties of various material systems. Recently, layered hybrid materials have largely been sought for greater control of functional properties. However, tribo-engineering with layered hybrid materials has not been well explored and has yet to be fully understood to advance moving mechanical components. Here, we develop a variety of layered hybrid materials based on a combination of multilayer graphene (mGR), multilayer graphene oxide (mGO), boron nitride (BN), and tungsten disulfide (WS2) and probe their tribological effectiveness using a ball-on-disk low-load tribometer. We demonstrate that solution-processed hybrid flakes coatings of BN and WS2 on stainless steel 304 (SS) are not tribologically resilient. However, when combined with mGO and mGR-based compositions, even BN and WS2-based hybrid flakes coatings reveal enhanced tribological performance due to synergistic effects. Developed BN_mGR and WS2_mGO binary hybrids, as well as BN_WS2_mGR and BN_WS2_mGO ternary hybrids, reduced friction by 32%, 59%, 29%, and 40%, respectively, compared to bare SS. We demonstrate that the WS2_mGO binary hybrid flakes coating yields a low coefficient of friction (COF) and high wear resistance. To further enhance its survival under rigorous tribological conditions, particularly at higher loads, we engineer its formulation. The resulting WS2_mGO_14 formulation exhibits the lowest friction with an average COF of ~ 0.09, reducing the friction of bare SS by 87%, and the highest wear resistance at a normal load of 0.1 N. Moreover, it maintained its tribological effectiveness at higher normal loads up to 4 N, outperforming all other hybrid flakes coatings and various other WS2_mGO formulations studied in this work. Microscopic and spectroscopic studies by FESEM, Raman, and FTIR are conducted to gain fundamental insight into friction and wear control mechanisms of the WS2_mGO hybrid. This work discovers that the inclusion of carbon-based layered material is mandatory to achieve low friction and high wear resistance in BN and WS2-based material systems and developing slippery surfaces.