Effect of TiB₂ and GNP reinforcements on machinability in drilling of Al7075/TiB₂/GNP hybrid composites produced by powder metallurgy

Abstract

In this study, it has been aimed to investigate the machinability performances by drilling by producing Al7075 matrix hybrid composite samples with graphenenanoplate (GNP) and titaniumdiboride (TiB2) reinforced at different rates by powder metallurgy. The impacts of GNP and TiB2 reinforcing materials on the cutting parameters and wear behavior of the cutting tool have been examined and discussed. As a result of the drilling tests which are carried out by applying different cutting parameters, it was observed that GNP additive has positive impact on the cutting forces, surface roughness, and hole quality in general. As a result of the machining experiments, the lowest cutting force was obtained as 150 N at a feed rate of 0.100 mm/rev and a cutting speed of 60 m/min in the 1% GNP reinforced sample. The minimum roughness value was obtained as 0.886 micron at 60 m/min cutting speed in the 1% GNP reinforced sample. The minimum deviations from cylindricality and circularity were also measured as 0.03 and 8.005 mm from the 1% GNP reinforced sample. While the lubricating effect was low with a GNP ratio of 0.5%, the abrasive effect was observed more with a GNP ratio of 1.5%. While GNP supplementation decreased the diameter deviation and cylindrical deviation values, it increased the perpendicularity deviation values. In general, swarf chip formation occurred with a small amount of flank wear on the cutting tools. While hard TiB2 reinforcement particles in the composite structure were effective in flank wear, the most important cause of chip formation was the presence of ductile aluminum matrix and relatively low cutting speeds. When the entire experimental study was evaluated, it was evaluated that the solid lubricant property of the GNP reinforcement material was effective at the most 1% GNP reinforcement rate.