Boosting lubricity and wear resistance via graphene oxide and graphene oxide-boron nitride composite systems

Abstract

Precise control of sliding interfaces is crucial to minimize friction and wear. For this purpose, two-dimensional (2D) materials have shown promising results which have sparked further interest in studying and engineering this material class for better tribological control. In this study, we explored the friction and wear characteristics of solution-processed monolithic flake coatings of hexagonal boron nitride (BN) and multilayer graphene oxide (mGO) at various concentrations. We chose BN and mGO as solid lubricants from the class of 2D materials due to their low shear strengths, which arise from their lamellar crystalline structures. Furthermore, the chemical and thermal stability of BN offers enhanced resistance to oxidative degradation. Additionally, we developed a highly lubricating and wear-resistant composite flake coating comprising BN and mGO (designated as BN_mGO), whose tribological effectiveness exceeds their individual counterparts. The friction and wear control efficacy of the BN_mGO composite flakes coating surpassed that of the monolithic BN flakes coatings and was found to be similar to or slightly better than the monolithic mGO flakes coatings fabricated at much higher solution concentrations. The BN_mGO composite achieved exceptional tribological performance with the lowest average coefficient of friction (∼0.28), suggesting ∼61.4 % reduction compared to bare stainless steel (SS). Raman and Fourier transform infrared spectroscopies, electron microscopy, and elemental mapping analyses of the wear track along with transmission electron microscopy analysis of the composite flakes coating were performed to elucidate the tribological mechanisms. There was evidence of the reduction of mGO to reduced mGO (rmGO) during the formation of the BN_mGO composite, which contributed to its enhanced lubricity and wear resistance. This phenomenon could potentially be leveraged in the development of other mGO-based binary or ternary composite coating systems to improve sliding contact performance and wear protection.