Plasma-sprayed graphene oxide reinforced alumina composite coatings on low carbon steel with improved fracture toughness, brittleness index, and microhardness

Abstract

In this work, the mechanical properties of atmospheric plasma-sprayed Al<inf>2</inf>O<inf>3</inf>and Al<inf>2</inf>O<inf>3</inf>-xGO (x = 0.5, 1.0, 1.5, and 2.0 wt%) coatings on low carbon steel was evaluated using the Vickers indentation technique, and the effects of GO addition in microhardness brittleness index and fracture toughness were investigated. The Fourier-transform infrared (FTIR) spectroscopy and Field Emission Scanning Electron Microscopy (FE-SEM) techniques were employed to analyze the microstructural characterization of the plasma-sprayed coatings and to confirm the retention of GO in the Al<inf>2</inf>O<inf>3</inf>-xGO composite after the plasma spray. It was found that the Vicker's microhardness of as-sprayed Al<inf>2</inf>O<inf>3</inf>is 4.148 GPa and it decreased with the increase in the addition of GO and for Al<inf>2</inf>O<inf>3</inf>-2.0GO, it is 3.305 GPa. The fracture toughness of Al<inf>2</inf>O<inf>3</inf>is 4.86 (MPa m1/2) whereas for Al<inf>2</inf>O<inf>3</inf>-2.0GO is 16.85 (MPa m1/2). The fracture toughness has increased whereas the brittleness index has decreased as the weight percentage of GO addition is increased in the Al<inf>2</inf>O<inf>3</inf>-GO composite. Thus, the plasma-sprayed Al<inf>2</inf>O<inf>3</inf>and Al<inf>2</inf>O<inf>3</inf>-xGO coatings suggest that 2 wt% GO addition helps in the improvement of brittleness, fracture toughness, and the microhardness. © 2020 Elsevier Ltd. All rights reserved.