1stInternational Conference of Advanced Materials and Manufacturing Technologies, Karabük, Türkiye, 25 - 27 Ekim 2017, cilt.1, no.1, ss.35-41
In this study, the drillability of Al/15B4C metal-matrix composites with untreated, cryogenically treated and cryogenically treated+tempered HSS twist drills has been evaluated with respect to tool life, tool wear and surface roughness. The machinability tests were performed with untreated (U), cryogenically treated (CT) and cryogenically treated and tempered (CTT) tools at three different cutting speeds (Vc:17, 21 and 26 m/min), at three different feed rate (f:0.06, 0.08 and 0.1 mm/rev) and under dry drilling conditions. First, following the applied cryogenic treatment, the change in the microstructures of the cutting tools was evaluated with scanning electron microscope (SEM) images taken from different points of each sample. At the second phase, the chip volume removed from the workpiece material was determined until the drilling ability of the tools came to an end. SEM images were taken in order to examine and determine the wear mechanisms and wear types emerged on the cutting edges as a result of the drilling tests. Finally, surface roughness of the hole walls were measured and the effects of drilling parameters and cryogenic treatment applied on the cutting tools were evaluated. In drilling of the Al/15B4C reinforced composites, the cryogenically treated (CT) and cryogenically treated+tempered (CTT) tools showed 50% improvement in tool life when compared to the untreated (CHT) tools. Outer corner and flank wear types were observed on the cutting tools after the drilling of Al/15B4C reinforced composite. While the cryogenically treated (CT) tools improved the surface roughness of the holes by approximately 1%, cryogenically treated+tempered (CTT) tools improved by approximately 10%.