Improved mechanical and wear properties of hybrid Al-Al2O3/GNPs electro-less coated Ni nanocomposite

Al was successfully reinforced with two ceramics Al2O3 coated Ni and graphene nanoplatelets (GNPs) coated Ni by electro-less deposition technique to form Al-Al2O3/x GNPs hybrid nanocomposite (x=0,0.2,0.6,1and 1.4%) with improved mechanical and wear properties. Compressive strength, hardness, wear properties and coefficient of friction were investigated. The results indicated that increasing GNPs volume fraction improves compressive strength, hardness and antifriction properties of composites significantly. In comparison with pure aluminum, 1.52- fold increases in the strength, 2.45-fold increase in the hardness and 19.2-fold decreases in the wear rate of Al-10%Al2O3/1.4%GNPs nanocomposite are achieved. This improvement is attributed to the remarkable mechanical strength and excellent self-lubrication of grapheme, the reduction of grain size during electro-less deposition process and the increased efficient stress transfer due to the curled structure of GNPs. Additionally, coating GNPs with Ni particles prevent the formation of Al3C4 intermetallic phase which lead to this large improvement in the wear rate. In comparison with the available results in the literature, electro-less coating of GNPs with Ni provides 2.1 times larger hardness than composite with uncoated GNPs.