Machinability Studies on Aluminium-Silicon Carbide-Graphite Hybrid Composites: A Focus on Drilling with HSS Tool

The study aims on the fabrication of AMMCs, which are aluminum 6061 (Al) matrices reinforced in varying weight proportions with silicon carbide and graphite. Additionally, using Taguchi's orthogonal array, drilling operations are carried out on the composites for various combinations of process parameters. The influence of four control factors such as spindle speed (S), feed rate (FR), diameter of drill (D) and % of silicon carbide (SiC) on surface roughness (Ra), circularity and cylindricity was investigated. Based on the experimental results, it is determined that the surface roughness and circularity of the hole at both the entry and exit are significantly influenced by cutting parameters. The lowest Ra was observed at moderate levels of the S and FR, i.e., 580 rpm and 0.575 mm/rev: 8 mm D and 2% SiC. Circularity gets worse as the spindle speed, feed rate and % SiC increase, i.e., at 1160, 1.25 mm/rev. and 8% respectively, with respect to the diameter of the drill bit, 8 mm is yielding larger circularity. However, cylindricity improves with an increase in speed from 300 rpm to 580 rpm and worsens with further increases in speed to 1160 rpm; moderate feed rate, i.e., 0.575 mm/rev, yields better cylindricity; however, lower and higher feed rates yield almost the same cylindricity. Further cylindricity gets worse as the increase in 'D'. Cylindricity improves with increasing % SiC and obtains good value at 8%.