Investigation of the machinability of carbon fiber reinforced plastic composites using thin film coated carbide tools

Carbon fiber reinforced polymer (CFRP) composites have been used in a wide range of applications including space, aviation and automotive industries owing to their superior characteristics such as high bearing capacity, strength, rigidity, low density and their lightness. Due to the abrasive structure of CFRP composites, cutting tools used in the milling of these materials complete their economic lifes in shorter periods as a result of short cyclic processes. Resulting tool wear induce structural failures such as delamination, fiber breakage, uncut fibers and surface roughness. Provision of optimum surface characteristics holds particular importance in fields such as aviation industry where surface quality has a substantial effect on quality of components. The aim of this thesis study was to increase the wear resistance and cutting performance of cutting tools, used in the contour milling of CFRP composites, by deposition of different type of nitride based compounds on carbide cutting tools with PVD (physical vapor deposition) method. The effect of use of cutting tools, PVD-coated with different nitride-based compounds, on the surface quality and dimensional accuracy of CFRP composite materials was also investigated. In the present research, uncoated carbide cutting tools, PVD coated nano-layer AlTiN/TiN, multilayer nano-composite TiAlSiN/TiSiN/TiAlN, single layer TiAlN and TiN cutting tools were tested with 100, 200 and 300 m/min cutting speeds, 0,05-0,15 and 0,25 mm feed per tooth feed-rate, and 1 mm cutting width. The resultant cutting force, average surface roughness, tool wear and delamination rates, resulting from milling experiments, were evaluated. In addition, following the machining process, cutting tools were subjected to scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and elemental mapping analyses to make an in-depth analysis of the coated cutting tools' surface microstructure. According to the obtained cutting force, average surface roughness and tool wear test results, the applied coating processes increased the machinability performance of cutting tools.