Effect of graphene coating on the microstructure and mechanical properties of tungsten inert gas surface melted AISI-316L steel

In this study, stainless steel substrates were coated with a graphene layer by a drop coating method. The surface of these graphene-coated samples was then modified using tungsten inert gas (TIG) surface melting technique. Phase changes, microstructure, microhardness, and wear properties of as-received (unprocessed), TIG surface-melted and graphene-coated TIG surface-melted specimens were inspected. Due to the inclusion of graphene, surface melting steered the creation of thick layers of iron-carbide (FeC) particles. The hardness of the graphene-coated melted layer depicted a high value of 420 HV, while the maximum hardness of the as-received surface melted layer was only 260 HV. Peak shifts observed in Raman spectroscopy depicts the disorderness developed in the graphene incorporated on the substrate. There is a reduction of ~14% in the specific wear rate with the incorporation of graphene coating due to its self-lubricating nature. As an outcome, as-received surface melted steel samples displayed relatively higher wear rates compared to those of surface melted graphene-coated specimens. The formation of a thin graphene tribolayer led to the reduction of the wear in the graphene-coated samples. Delamination, grooves, abrasive wear were observed on the as-received surface melted specimens where a very rough surface was obtained against the graphene-coated one.