Tribological Behaviour of Plasma-Sprayed Graphene Nanoplatelets Reinforced Hydroxyapatite Nanocomposite Coating

We aim to understand the tribological properties of graphene nanoplatelets (GNPs) reinforced hydroxyapatite (HA) composite coating synthesized using plasma spray on Ti alloy substrate (Ti-6Al-4 V). A significant reduction of 83% in wear volume loss is observed on addition of 2 wt. % GNPs in HA as compared to bare HA coating, respectively. Similarly, coefficient of friction (COF) shows the relative reduction of 70% is HA-2 wt. % GNP coating. Post-wear analysis by Raman spectroscopy confirms the retention of GNPs with the enlarged defect over the worn surface. FE-SEM investigation of worn surface shows the strengthening mechanism such as GNP bridging, GNP pull-out which could be attributed to enhanced wear resistance of the coating. GNPs induced lubrication has been observed as the prime reason for lower COF of the worn surface.