EXPERIMENTAL INVESTIGATION ON TAPPING OF Al6061/SiC METAL MATRIX COMPOSITE WITH 2 AND 4 MICRONS TiAlN COATED STRAIGHT FLUTED HSS MACHINE TAPS

The objective of this work is to evaluate the performance of straight fluted HSS machine taps with 2 microns and 4 microns thickness of TiAlN coating on tapping of Al6061/SiC metal matrix composite. The methodology includes the fabrication of Al6061/SiC Metal matrix composite by stir casting process with 5, 7.5 and 10 weight percent SiC particles. Tapping operation was performed under dry conditions with different cutting speed and constant feed rate equal to the pitch of the thread. The specimens were drilled and tapped with HSS M8X1.25 machine taps coated with TiAlN coating of 2 and 4 micron thickness, in a CNC vertical machining center. The performance of HSS machine taps was evaluated in terms of tapping torque, tool flank wear, and quality of threads produced. Torque and thrust were measured using a drill tool dynamometer of Kistler make. Quality of threaded holes was analyzed by capturing the thread profile using a metallurgical microscope. The estimation of progressive flank wear of HSS machine taps was done using the profile projector. Increase in weight percentage of SiC particles and tapping speed would increase the torque required for tapping, rate of flank wear of the tool and decrease the quality of threaded holes. The progressive flank wear was found higher in machine taps with 2 microns thickness of TiAlN coating when compared to taps with 4 microns thickness of TiAlN coating. Influence of cutting speed on progressive flank wear of HSS machine tap was found to be higher compared to the thickness of TiAlN coating on the tap and weight percentage of SiC.