Browsing by Author "Durkaya, Göksel"

Now showing 1 - 8 of 8

Citation Count: 5
The adhesion and tribological properties of c-BN films deposited by high power impulse magnetron sputtering
(Elsevier Sci Ltd, 2019) Efeoglu, Ihsan; Totik, Yasar; Keles, Aysenur; Gulten, Gokhan; Ersoy, Kivilcim; Durkaya, Goksel; Department of Metallurgical and Materials Engineering
Nitride based films are very important for industrial applications due to their mechanical and tribological properties. Among the nitride based films, c-BN films have superior properties. But, the adhesion properties of c-BN films deposited using magnetron sputtering with different power sources are inadequate generally. Recently, High Power Impulse Magnetron Sputtering (HiPIMS) power sources have been used to increase the adhesion of coatings and there is no open literature about c-BN deposited using HiPIMS. From this point, c-BN films were coated on 4140 steels using HiPIMS with closed-field unbalanced magnetron sputtering (CFUBMS). In the process, two B4C, two Ti targets and Ar + N-2 gas mixture were used to synthesize c-BN films. The amount of N-2 was altered as 2.5, 3.5 and 4.5sccm. The characteristic properties of c-BN films were analyzed using SEM, XRD and FT-IR. The mechanical properties were tested using a microhardness and scratch testers. The tribological properties were performed by a pin-on-disc tribotester under atmosphere, argon, and oil test conditions. The results showed that the properties of c-BN films deposited by HiPIMS are interesting. The hardness values were obtained above 36 GPa and the maximum critical load was reached to 80 N. Also, the minimum CoFs were observed as expected from the oil condition, in that case, the lowest CoF (mu congruent to 0.06) was noted from the hardest coating.
Citation Count: 0
Characterization of Thin Film Boron Nitride Coatings and Observation of Graphite-Like Boron Nitride
(Polish Acad Sciences inst Physics, 2019) Durkaya, G.; Efeoglu, I.; Ersoy, K.; Cetin, B.; Kurtuldu, H.; Department of Metallurgical and Materials Engineering
Cubic boron nitride is a coating solution to improve wear performances in demanding engineering applications. In order to achieve the best performance from this thin film system, the physical dynamics behind the phase compositions, phonon dynamics, surface quality, interfacial effects and stoichiometric relations should be understood. In this study, for this purpose, physical vapor deposition grown BN thin films were studied in detail using the Raman spectroscopy, atomic force microscopy, and scanning electron microscopy techniques.
Citation Count: 0
Investigating the Effect of Auto-Focus and Auto-Threshold Algorithms in Advanced Nodularity Analysis of Austempered Ductile Iron Castings
(Polish Acad Sciences inst Physics, 2019) Cetin, B.; Kurtuldu, H.; Durkaya, G.; Davut, K.; Department of Metallurgical and Materials Engineering
Austempered ductile iron castings have a wide range of application fields including defense and heavy-duty industries due to their promising mechanical properties. Austempered ductile iron castings could provide excellent combination of high strength, toughness, and wear resistance at the same time. Unlike other spheroidal ductile cast irons, austempered ductile iron castings need to be processed by a special austempering heat treatment which enables the verification of the conformity of the nodularity level after the casting operations. Previous studies have shown that wide area mappings for determining nodularity are crucial to eliminate the representativeness problems. In this sense, some precautions should be taken for the accuracy of results in large scale nodularity examination. In this study, the effect of auto-thresholding and auto-focusing algorithms on the advanced nodularity analysis is investigated. The results suggest that auto-thresholding and auto-focusing methods have significant contributions for determining average nodularity levels and average graphite sizes.
Citation Count: 0
Low cost, ultra-high throuhput particle counting using inertial microfluidics
(Chemical and Biological Microsystems Society, 2016) Çetin,B.; Kaplan,H.; Durkaya,G.; Kurtuldu,H.; Department of Metallurgical and Materials Engineering
In this work, an ultra-high throughput microfluidic particle counting system is demonstrated. For the particle counting, a low cost custom-design optical hardware is developed. The microfluidic chip utilizes the inertial microfluidics to focus the particles in a certain location which significantly enhanced the optical signal utilized for the quantification of the number concentration. The effect of the particle focusing on the counting performance is demonstrated. The proposed system has a potential to be portable and has a capability to process 10 ml of sample within couple minutes.
Citation Count: 0
Non-Invasive 3D Optical Measurement of Round Surfaces
(Polish Acad Sciences inst Physics, 2019) Kurtuldu, H.; Durkaya, G.; Cetin, B.; Department of Metallurgical and Materials Engineering
Precise measurement of wear profiles in large areas of round surfaces such as shafts, suspension bars and high-deviation geometry surfaces is a challenge in manufacturing engineering. An optical measurement method is developed to overcome this challenge. This method, relying on angular reconstruction of scattered light profiles, is used for the measurement of irregular wear in quality testing of round surfaces which provides information on estimating the surface lifetime after prolonged use. This approach achieves a 3D depth accuracy better than 50 mu m in suspension bars with diameters up to 50 mm from an imaging distance of 250 mm.
Özgün bir raman spektroskopi sistemi geliştirilmesi
(2018) Al-ızaybawee, Ammar M-hasan Nassoom; Durkaya, Göksel; Kurtuldu, Hüseyin; Department of Metallurgical and Materials Engineering
Raman spektroskopisi, materyallerle doğrusal olmayan ışık etkileşimini kullanan tahribatsız bir optik ölçüm tekniğidir. Bir numunenin moleküler yapısını ve kimyasal maddelerini spektral imzalarından tanımlamak için kullanılan başlıca spektroskopik tekniklerden biridir. Bu tezde, metalurjik numuneyi incelemek için ev yapımı bir Raman spektrometresi geliştirilmiştir. Sistem standart organik numuneler kullanılarak kalibre edilmiş ve ince film kaplamalarının analizi için kullanılmıştır. Metin boyunca, büyük örneklerin analizinde ve haritalama analizlerinde kullanılabilecek olası tarama tasarım kavramları da tartışılmıştır.
Citation Count: 2
Synthesis and investigation of structural-mechanical-tribological properties of c-BN based BN thin films
(2017) Efeoğlu, İhsan; Totik, Yaşar; Keleş, Ayşenur; Ersoy, Kıvılcım; Durkaya, Göksel; Department of Metallurgical and Materials Engineering
C-BN films are candidate material to diamond due to their promising properties. Although some properties of c-BN films are better than diamond, adhesion properties between the substrate and the film are very poor. In this study, c-BN films were deposited by closed-field unbalanced magnetron sputtering system onto 4140 steels in Ar/N2 atmosphere. The c-BN films coated in three different N2flow rates. The coated specimens were characterized by SEM and X-ray diffraction techniques. The bonding state of B, N and C elements were obtained using XPS. The mechanical properties of the c-BN films were tested by micro-indentation. The adhesion properties between substrate and the film were investigated by using scratch test. The tribological properties were carried out using pin-on-disc in atmospheric conditions. Our results showed that the c-BN films exhibited very dense and columnar microstructure. The maximum critical load was read 23 N in the softest c-BN film. The maximum and minimum hardness were measured 69 GPa and 33 GPa, respectively. When the hardness was increased the friction coefficient was decreased. The lowest friction coefficient (0.15) was obtained from the hardest film and the highest friction coefficient (0.65) was obtained from the lowest hardness
Citation Count: 1
Wear resistance performance of boron nitride coatings on end milling cutters
(Inderscience Publishers, 2017) Çetin,B.; Durkaya,G.; Kurtuldu,H.; Hacaloglu,T.; Gurbuz,M.; Kaftanoǧlu,B.; Department of Metallurgical and Materials Engineering; Information Systems Engineering
For defence industry applications, the machining of ultra-high strength steels or aluminium with ballistic temper grades is a widely-used operation. Therefore, it is a great challenge to find an optimum solution for tool wear. In that sense, tool coatings provide various solutions for machining of hard materials or improving wear resistance. A cost-effective tool coating provides longer tool life, hence decreases the tool cost contribution in production. Boron nitride (BN) coating could be thought as a new generation coating method compared to titanium nitride (TiN), aluminium titanium nitride (AlTiN) or silicon aluminium oxy-nitride (SiAlON). BN coating material has a great strength, toughness and chemical stability whereas it has an important disadvantage of high intrinsic stress. In this industrial study, standard end mill cutters are coated with BN material by physical vapour deposition (PVD) method. The coated and uncoated milling tools are compared according to their wear resistance and the obtained workpiece surface roughness. First results of the study are presented in this paper. © 2017 Inderscience Enterprises Ltd.