Abstract: Surfaces of B19 Al-alloy, a drill-pipe material in petroleum industry, were modified by micro-arc oxidation(MAO) in graphene-added electrolyte.The influence of the graphene-content on the microstructures, phases and tribological properties was investigated with X-ray diffraction, scanning electron microscopy, Raman spectroscopy and conventional mechanical probes.The results show that the graphene addition had a major impact.For example, the graphene-addition resulted in many significant changes, including: i) formation of higher density of α-Al₂O₃ and γ-Al₂O₃ phased smaller grains in the smoother, more compact and thicker(3.96 μm) MAO-coatings with fewer micro pores; ii) a six-time stronger hardness and a lower wear-rate than that of Al-alloy; iii) a decrease of friction coefficient down to 0.67 and reduced surface roughness.Possible mechanisms responsible for the improvement of tribological properties were also tentatively discussed in a thought provoking way.