Enhanced graphene oxide adhesion on steel surface through boronizing functionalization treatment: Toward the robust ultralow friction

As a promising lubricate additive, the excellent lubrication performance of graphene oxide (GO) is attributed to the formation of GO tribofilm. However, the poor adsorption of GO on engineering materials surfaces limits the formation of tribofilm, resulting in losing the expected lubricating performance as a lubricant additive. In this study, to improve the adsorption of GO on bearing steel, the boronized functionalization layer was prepared on a bearing steel surface by an electrochemical boronizing process. Our experiment results indicate that an ultralow friction state with a friction coefficient (COF) of 0.03 was achieved on the boronized surface lubricated with 1 wt% GO nanosheets as water-based additives. Together with TEM, EDS and Raman analysis, we confirmed the formation of GO tribofilm with a thickness of 280 nm on the sliding surface due to the synergistic effect of the boronized surface and GO. Molecular dynamics (MD) simulation revealed that the high adhesion energy between the boronized surface and GO endows the preferential adsorption of GO on the sliding surface to form the tribofilm. The ultralow interlayer shear strength of GO tribofilm further contributed to the impressive synergistic lubrication performance. Our study expands the application scope of the ultralow friction behavior of GO by enhancing its adhesion energy on the engineering alloy surface.