Alumina-graphene nanocomposite coatings fabricated by suspension high velocity oxy-fuel thermal spraying for ultra-low-wear

Abstract

An alumina coating containing 1wt.% graphene nanoplatelets (GNPs) is deposited for the first time by suspension high velocity oxy-fuel (SHVOF) thermal spraying – an emerging coating deposition technique. Raman spectroscopy shows the GNPs survive the process albeit with a two-fold increase in the density of defects in the graphitic lattice. Dry-sliding wear testing at a 10N load yields a two order of magnitude reduction in the specific wear rate for the alumina/GNP composite in comparison to the equivalent pure alumina coating. Testing with varying loads shows that the transition to the severe wear regime is prevented until between 30 and 35N for the alumina+GNP coating which otherwise occurs between 5 and 7.5N in the absence of GNPs. A reinforced microstructure, and specifically fracture toughness, explains the improved wear behaviour as opposed to tribofilm formation.