Development of High Fracture Toughness Hard Coatings

Kaygusuz, Burçin
Improving the machining performance of cutting tools is critical for increasing product quality and decreasing production cost and time. For this purpose, hard coatings on cutting tools are widely utilized in the industry. These hard coatings increase the lifetime of cutting tools by improving their wear resistance and allow higher cutting speeds. One of the primary drawbacks of these hard coatings is their brittle nature, which occasionally results in premature failure. This thesis investigated a solution to this problem through the development of new generation hard coatings. For this purpose, W and Mo alloying additions were made to conventional coating compositions such as AlTiN and AlCrN, based on the predictions of density functional theory calculations (DFT). The thesis study considered two different coating methods: magnetron sputtering (MS), suitable for lab-scale studies, and cathodic arc evaporation (CAE), suitable for industrial purposes. X-ray Diffraction, Scanning Electron Microscopy, and Energy Dispersive X-ray Spectroscopy characterized the coatings and nanoindentation measurements provided the hardness and fracture toughness values. In addition, new generation fracture toughness measurements based on microcantilever bending tests were employed for more accurate quantification of the fracture behavior. Lastly, selected coatings were subjected to drilling and ball-on disc tests to clarify their performance in actual working conditions. The results show that especially W additions provide at least an order of magnitude increase in fracture toughness combined with dramatic increases in tool lifetime. Therefore, the thesis results demonstrated an effective route to the development of new high-performance coatings for wear resistance applications. Future studies on optimizing the process parameters for cathodic arc evaporation will enable the wider utilization of the developed coatings in industry.


Analytical modeling of spindle-tool dynamics on machine tools using Timoshenko beam model and receptance coupling for the prediction of tool point FRF
Erturk, A.; Özgüven, Hasan Nevzat; Budak, E. (2006-12-01)
Regenerative chatter is a well-known machining problem that results in unstable cutting process, poor surface quality and reduced material removal rate. This undesired self-excited vibration problem is one of the main obstacles in utilizing the total capacity of a machine tool in production. In order to obtain a chatter-free process on a machining center, stability diagrams can be used. Numerically or analytically, constructing the stability lobe diagram for a certain spindle-holder-tool combination implies...
Recent developments in industrial applications of nanoemulsions
ÖZOĞUL, YEŞİM; Karsli, Gokcem Tonyali; DURMUŞ, MUSTAFA; YAZGAN, HATİCE; Öztop, Halil Mecit; McClements, David Julian; ÖZOĞUL, FATİH (2022-06-01)
© 2022 Elsevier B.V.Nanotechnology is being utilized in various industries to increase the quality, safety, shelf-life, and functional performance of commercial products. Nanoemulsions are thermodynamically unstable colloidal dispersions that consist of at least two immiscible liquids (typically oil and water), as well as various stabilizers (including emulsifiers, texture modifiers, ripening inhibitors, and weighting agents). They have unique properties that make them particularly suitable for some applica...
Application of the Contour Method to Determine Axial Residual Stresses in Cold Extruded Steel Rods
Aydin, O.; Şimşir, Caner (2021-01-01)
Residual stresses in cold extruded parts play an important role in both component lifetime and succeeding in manufacturing performance. When a cold extruded part is used directly, the lifetime of the part depends on the residual stresses induced during cold extrusion. On the other hand, if the part is exposed to post operations such as machining, residual stresses may cause distortions. Despite their importance, there are only a few residual stress measurement methods to assess axial residual stresses in fu...
An investigation on dynamic contact parameters in machining center spindle tool assemblies
Özşahin, Orkun; Özgüven, Hasan Nevzat; Department of Mechanical Engineering (2008)
In machining centers, with the increasing trends in high precision machining, chatter has become an important problem which results in poor surface finish and low material removal rate. Chatter can be avoided with stability diagrams which provide the stable regions in the machining process for the depth of cut and spindle speed combinations. In order to obtain stability diagrams, tool point frequency response function (FRF) of the system should be obtained. Throughout this study, contact parameters which ar...
Simulator of an additive and subtractive type of hybrid manufacturing system
Dilberoğlu, Mecid Uğur; Yaman, Ulaş; Dölen, Melik (2019-06-24)
Additive Manufacturing (AM) facilitates the production of intricate objects despite its weakness in attainable part quality and fabrication speed compared to the conventional manufacturing methods. To alleviate the problems arising as a natural outcome of AM methods, hybrid technologies become viable options by employing concurrent manufacturing procedures, e.g. synergetic additive and subtractive manufacturing (SM) actions. Hybrid workstations have recently opened up new dimensions to 3D-printing industry,...
Citation Formats
B. Kaygusuz, “Development of High Fracture Toughness Hard Coatings,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.