Investigation of cutting performance and wear behavior of nanolayer AlTiN/TiN coated carbide cutting tools during milling of Ti6Al4V alloy

Ti6Al4V titanium alloys are widely used in the aerospace and medical industries due to their high temperature resistance and biological adaptation. However, carbide cutting tools wear rapidly and complete their lifetime because of high cutting temperatures and build-up edge formation on the tool surface during machining of this material. In this study, nanolayer AlTiN/TiN coatings were deposited on the carbide tools to enhance the wear resistance and service life of these tools. In addition, to eliminate the need to use coolant consumption through enabling dry machining and thus to decrease the machining costs are among the goals of this study. In order to compare the wear behavior and cutting performance of the nanolayer AlTiN/TiN coatings, single layer TiN and single layer TiAlN coatings are also deposited on the carbide tools. It is important to determine properties of the nanolayer AlTiN/TiN coatings (such that microhardness, adhesion to the substrates and friction) and also to introduce their cutting performances in order to indicate machining conditions of these coated tools in machining industry. Therefore, in this thesis, after the nanolayer AlTiN/TiN coating was deposited on the substrate materials and carbide cutting tools using physical vapor deposition method, their microhardness with nanoidentation, their adhesion to the substrate material with scratch test and their friction coefficients with ball on disc method were determined. Performing face milling tests on Ti6Al4V alloy, the effect of the nanolayer AlTiN/TiN coating on cutting performance and wear behavior of the carbide cutting tools was examined. Also, cutting parameters' influence on cutting forces and workpiece surface roughness were determined. Wear mechanisms and wear types were revealed by performing SEM and EDS analysis on the worn cutting tools. When compared to the coated and uncoated carbide tools, the nanolayer AlTiN/TiN coated tools gave 1,2-4,0 times longer lifetime. A remarkable positive effect of the nanolayer AlTiN/TiN coating on cutting forces and workpiece surface roughness was not observed.