Browsing by Author "Konca, Erkan"

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Citation Count: 24
Effect of electrodeposition parameters on the current density of hydrogen evolution reaction in Ni and Ni-MoS2 composite coatings
(2013) Saralog̀lu Güler,E.; Konca,E.; Karakaya,I.; Metallurgical and Materials Engineering
Nickel composites with co-deposited insoluble, solid lubricant particles such as MoS2 have been reported to reduce friction. It is known that hydrogen evolution reaction (HER), competes with nickel deposition. The influence of the parameters and their interaction effects on the peak current density of HER during the electrodeposition of Ni and Ni-MoS2 composite coatings were studied by fractional factorial design. The parameters and their ranges studied were; MoS2 particle concentration (0-30 g/l), temperature (30-50°C), pH (2-4) and two surfactants, namely; ammoniumlignosulfonate (ALS) and depramin-C (DC) (0-1 g/l). Electrodeposition processes were carried out from a typical Watts bath containing leveler, wetting agent and brightener by using a potentiostat. The peak current densities (ip) were extended to higher values and the peaks onlinear sweep voltammograms became noticeable by increasing the scan rate from 20 mV/s to 100 mV/s over the range of 0 to 2.5 V. The peak current densities (ip) of HER for each experimental route were determined by fractional factorial design for two mineral processing surfactants; ammoniumlignosulfonate (ALS) and depramin-C (DC) using a statistical analysis software named Minitab [1]. Adding MoS2, decreasing temperature and increasing pH had decreasing effects on the peak current density of HER regardless of the surfactant used. On the other hand, the surfactants increased the peak current density. © 2013 by ESG.
Citation Count: 23
Effect of Electrodeposition Parameters on the Current Density of Hydrogen Evolution Reaction in Ni and Ni-MoS₂ Composite Coatings
(Esg, 2013) Gueler, E. Saraloglu; Konca, E.; Karakaya, I.; Metallurgical and Materials Engineering
Nickel composites with co-deposited insoluble, solid lubricant particles such as MoS2 have been reported to reduce friction. It is known that hydrogen evolution reaction (HER), competes with nickel deposition. The influence of the parameters and their interaction effects on the peak current density of HER during the electrodeposition of Ni and Ni-MoS2 composite coatings were studied by fractional factorial design. The parameters and their ranges studied were; MoS2 particle concentration (0-30 g/l), temperature (30-50 degrees C), pH (2-4) and two surfactants, namely; ammoniumlignosulfonate (ALS) and depramin-C (DC) (0-1 g/l). Electrodeposition processes were carried out from a typical Watts bath containing leveler, wetting agent and brightener by using a potentiostat. The peak current densities (i(p)) were extended to higher values and the peaks on linear sweep voltammograms became noticeable by increasing the scan rate from 20 mV/s to 100 mV/s over the range of 0 to 2.5 V. The peak current densities (i(p)) of HER for each experimental route were determined by fractional factorial design for two mineral processing surfactants; ammoniumlignosulfonate (ALS) and depramin-C (DC) using a statistical analysis software named Minitab [1]. Adding MoS2, decreasing temperature and increasing pH had decreasing effects on the peak current density of HER regardless of the surfactant used. On the other hand, the surfactants increased the peak current density.
Citation Count: 0
Effect of electroplating parameters on "HER" current density in Ni-MoS2 composite plating
(Minerals, Metals and Materials Society, 2012) Güler,E.S.; Karakaya,I.; Konca,E.; Metallurgical and Materials Engineering
Nickel composites with co-deposited insoluble, solid lubricant particles such as MoS2 have been reported to reduce friction. It is known that hydrogen evolution reaction (HER), competes with nickel deposition. The influence of the electroplating parameters and their interaction effects on the peak current density for HER were studied by fractional factorial design. The parameters and their ranges were; MoS2 concentration (0-30 g/l), temperature (30-50°C), pH (2-4) and surfactants (0-1 g/l). Electrodeposition processes were carried out from a typical Watts bath containing leveler, wetting agent and brightener by using a potentiostat. The peak currents (I p) were extended to higher values and the peaks on linear sweep voltammograms became noticeable by increasing the scan rate from 20 mV/s to 100 mV/s over the range 0 to 2.5 V. The peak current densities (ip) for each experimental route were determined by fractional factorial design for three types of mineral processing surfactants; sodiumlignosulfonate (SLS), depramin-C (DC) and ammoniumlignosulfonate (ALS) using Minitab program [1]. Adding MoS2, decreasing temperature and increasing pH has decreasing effect on peak current density for all surfactants. ALS and DC have increasing effect whereas SLS has descending effect on peak current.
Citation Count: 0
EFFECT OF ELECTROPLATING PARAMETERS ON "HER" CURRENT DENSITY IN Ni-MoS₂ COMPOSITE PLATING
(Minerals, Metals & Materials Soc, 2012) Guler, Ebru Saraloglu; Karakaya, Ishak; Konca, Erkan; Metallurgical and Materials Engineering
Nickel composites with co-deposited insoluble, solid lubricant particles such as MoS2 have been reported to reduce friction. It is known that hydrogen evolution reaction (HER), competes with nickel deposition. The influence of the electroplating parameters and their interaction effects on the peak current density for HER were studied by fractional factorial design. The parameters and their ranges were; MoS2 concentration (0-30 g/l), temperature (30-50 degrees C), pH (2-4) and surfactants (0-1 g/l). Electrodeposition processes were carried out from a typical Watts bath containing leveler, wetting agent and brightener by using a potentiostat. The peak currents (I-p) were extended to higher values and the peaks on linear sweep voltammograms became noticeable by increasing the scan rate from 20 mV/s to 100 mV/s over the range 0 to 2.5 V. The peak current densities (i(p)) for each experimental route were determined by fractional factorial design for three types of mineral processing surfactants; sodiumlignosulfonate (SLS), depramin-C (DC) and ammoniumlignosulfonate (ALS) using Minitab program [1]. Adding MoS2, decreasing temperature and increasing pH has decreasing effect on peak current density for all surfactants. ALS and DC have increasing effect whereas SLS has descending effect on peak current.
Citation Count: 0
Effect of electroplating parameters on internal stress in ni-m0s2 composite plating
(Wiley Blackwell, 2013) Güler,E.S.; Konca,E.; Karakaya,I.; Metallurgical and Materials Engineering
[No abstract available]
Citation Count: 1
Effect of electroplating parameters on internal stress in Ni-MoS 2 composite plating
(2013) Saraloǧlu Güler,E.; Konca,E.; Karakaya,I.; Metallurgical and Materials Engineering
[No abstract available]
Citation Count: 23
Effects of Alloying Elements (Mo, Ni, and Cu) on the Austemperability of GGG-60 Ductile Cast Iron
(Mdpi, 2017) Konca, Erkan; Tur, Kazim; Koc, Erkin; Metallurgical and Materials Engineering; Department of Metallurgical and Materials Engineering
The interest in austempered ductile irons (ADI) is continuously increasing due to their various advantageous properties over conventional ductile irons and some steels. This study aimed to determine the roles of alloying elements Ni, Cu, and Mo, on the austemperability of GGG-60 ductile cast iron. Two different sets of GGG-60 (EN-GJS-600-3) samples, one set alloyed with Ni and Cu and the other set alloyed with Mo, Ni, and Cu, were subjected to austempering treatments at 290 degrees C, 320 degrees C, and 350 degrees C. A custom design heat treatment setup, consisting of two units with the top unit (furnace) serving for austenitizing and the 200 L capacity bottom unit (stirred NaNO2-KNO3 salt bath) serving for isothermal treatment, was used for the experiments. It was found that austempering treatment at 290 degrees C increased the hardness of the Ni-Cu alloyed GGG-60 sample by about 44% without causing a loss in its ductility. In the case of the Mo-Ni-Cu alloyed sample, the increase in hardness due to austempering reached to almost 80% at the same temperature while some ductility was lost. Here, the microstructural investigation and mechanical testing results of the austempered samples are presented and the role of alloying elements (Mo, Ni, and Cu) on the austemperability of GGG-60 is discussed.
Citation Count: 22
Effects of current density, coating thickness, temperature, pH and particle concentration on internal stress during Ni-MoS₂ electrocodeposition
(Taylor & Francis Ltd, 2014) Guler, E. Saraloglu; Karakaya, Ishak; Konca, Erkan; Metallurgical and Materials Engineering
Internal stress in plated deposits has been a common problem that may affect the functionality of coatings. Electrodeposition parameters and insoluble particles modify the characteristics and the level of internal stress of coatings. The influence of the electrocodeposition parameters and their interaction effects on the internal stress during the electrodeposition of Ni and Ni-MoS2 composite coatings were studied by fractional factorial design. The parameters studied and their ranges were: MoS2 particle concentration (0-10 g L-1), temperature (30-50 degrees C), pH (2-4), current density (1.2-4.8 A dm(-2)), and coating thickness (25-50 mu m). MoS2 addition into Watts bath resulted in the decrease in the tensile internal stress values or even changed the stress character from tensile to compressive. Moreover, low stress values were obtained when pH was 2 and coating thickness was 50 mu m.
Citation Count: 17
Investigation of the tribological behaviour of electrocodeposited Ni-MoS2 composite coatings
(Inderscience Publishers, 2017) Güler,E.S.; Konca,E.; Karakaya,I.; Metallurgical and Materials Engineering
Composite electroplating of solid lubricants in a metal matrix is an effective way to lower coefficient of friction (COF) and improve wear resistance of surfaces in sliding contact. In this work, Ni-MoS2 composite coatings were deposited on AISI 304 stainless steel substrates by electroplating from Watts bath containing suspended MoS2 particles and their tribological behaviour was studied. The effects of MoS2 particle concentration (5, 10 and 30 g/l), MoS2 particle size (1.440 and 5.156 μm), pH (2, 3 and 4), current density (3.8, 4.8 and 5.8 A/dm2) and the surfactant (sodium lignosulfonate, SLS) concentration (0.3 and 1 g/l) on the tribological behaviour were investigated using a ball-on-disc tribometer at ambient conditions. Lower current density, smaller particle size and higher concentration of MoS2 decreased COF. While increasing the surfactant concentration decreased the COF, its friction lowering effect was much more pronounced at relatively lower concentrations of MoS2 in the electrolyte. Copyright © 2017 Inderscience Enterprises Ltd.
Citation Count: 16
Investigation of the tribological behaviour of electrocodeposited Ni-MoS₂ composite coatings
(inderscience Enterprises Ltd, 2017) Guler, Ebru Saraloglu; Konca, Erkan; Karakaya, Ishak; Metallurgical and Materials Engineering
Composite electroplating of solid lubricants in a metal matrix is an effective way to lower coefficient of friction (COF) and improve wear resistance of surfaces in sliding contact. In this work, Ni-MoS2 composite coatings were deposited on AISI 304 stainless steel substrates by electroplating from Watts bath containing suspended MoS2 particles and their tribological behaviour was studied. The effects of MoS2 particle concentration (5, 10 and 30 g/l), MoS2 particle size (1.440 and 5.156 mu m), pH (2, 3 and 4), current density (3.8, 4.8 and 5.8 A/dm(2)) and the surfactant (sodium lignosulfonate, SLS) concentration (0.3 and 1 g/l) on the tribological behaviour were investigated using a ball-on-disc tribometer at ambient conditions. Lower current density, smaller particle size and higher concentration of MoS2 decreased COF. While increasing the surfactant concentration decreased the COF, its friction lowering effect was much more pronounced at relatively lower concentrations of MoS2 in the electrolyte.
KBB yöntemiyle alüminize edilmiş Inconel 718 ve Inconel 738LC süperalaşımların yüksek sıcaklık oksitlenme davranışlarının araştırılması
(2022) Telbakiroğlu, Yusuf Burak; Konca, Erkan; Metallurgical and Materials Engineering
Bu çalışma alüminize edilmiş Inconel 718 ve Inconel 738LC nikel bazlı süper alaşımların yüksek sıcaklık oksitlenme davranışlarını araştırmak ve karşılaştırmak amacıyla gerçekleştirilmiştir. Kaplamasız ve yüksek aktivite kimyasal buhar biriktirim (KBB) yöntemiyle alüminize edilmiş Inconel 718 ve Inconel 738LC numuneler 200 saat boyunca 925, 1000 ve 1050°C sıcaklıklarda havada oksitlenmeye maruz bırakılmıştır. Numunelerin oksidasyon mekanizmalarını araştırmak ve değerlendirebilmek amacıyla detaylı kesit incelemeleri, elementel analizler, ağırlık değişimi ölçümleri ve x-ışını kırınım çalışmaları yapılmıştır. Alüminizasyon sırasında numunelerin yüzeyinde oluşan NiAl fazının üstünde koruyucu Al2O3 tabakası oluşumu sayesinde hem 718 hem de 738LC alaşımında oksidasyon direncinin önemli ölçüde iyileştiği gözlemlenmiştir. Alüminizasyonun faydalı etkisinin tüm test sıcaklıklarında daha düşük oksidasyon hızı gösteren 738LC alaşımı numunelerde daha belirgin olduğu bulunmuştur. 738LC alaşımı altlığın daha yüksek alüminyum içeriğine sahip olmasının alüminyumun NiAl fazından difüzyon yoluyla uzaklaşmasını yavaşlattığı ve böylece bu alaşımın daha üstün oksidasyon direnci göstermesindeki ana neden olduğu öne sürülmüştür.
Citation Count: 8
Mechanical behavior of anodic alumina coatings reinforced with carbon nanofibers
(Springer, 2009) Kothari, Abhishek K.; Konca, Erkan; Sheldon, Brian W.; Jian, Kengqing; Li, Hao; Xia, Zhenhai; Hurt, Robert; Metallurgical and Materials Engineering
Anodic alumina was reinforced with three types of carbon nanofibers differing in the orientation of their graphene structure-perpendicular to the fiber axis, and parallel to the fiber axis both with dense core and hollow core (i.e., nanotubes). This study was designed to identify potential toughening and damage tolerant mechanisms in these nanoscale fiber-reinforced composite coatings. The dense carbon fibers improved contact damage resistance and reduced frictional resistance in sliding contacts. The hollow core reinforcements were much more promising for improving the fracture toughness of the composite coatings.
Citation Count: 1
ÖSTENİTLEME SICAKLIĞININ EN-GJS-600-3 KÜRESEL GRAFİTLİ DÖKME DEMİRİN ÖSTEMPERLENME DAVRANIŞINA ETKİLERİNİN ARAŞTIRILMASI
(2020) Konca, Erkan; Tur, K Zım; Metallurgical and Materials Engineering; Department of Metallurgical and Materials Engineering
Bu çalışmada östenitleme sıcaklığının EN-GJS-600-3 (GGG-60) küresel grafitli dökme demirinöstemperlenme davranışına etkisi araştırılmıştır. Y bloklarına dökülen % 0,5 Cu alaşımlı EN-GJS-600-3küresel grafitli dökme demirden çıkarılan numuneler kullanılarak iki farklı östenitleme sıcaklığı (850 ve950°C) ve iki farklı östemperleme sıcaklığının (290 ve 320°C) dört ayrı kombinasyonunda östemperlemedeneyleri yapılmıştır. Östemperleme deneyleri sonrası numunelerin sertlik ölçümleri, çekme testleri ve içyapı incelemeleri gerçekleştirilmiştir. Her iki östemperleme sıcaklığında da 950°C’de östenitlenmişnumunelerde 850°C’de östenitlenmiş numunelere göre daha yüksek sertlik, akma ve çekme dayanımıdeğerlerine ulaşılmıştır. Bu sonuçlar, 950°C’de yapılan östenitlemenin 850°C’ye göre östenit matris içindehem daha çok karbonun çözünmesini hem de östenitin daha iri taneli olmasını sağlayaraköstemperlenmeye daha elverişli östenit yapısı oluşturabilmesiyle ilişkilendirilmiştir.
Tel ark eklemeli imalat yöntemiyle dubleks paslanmaz çelik plaka üretiminde proses parametrelerinin optimizasyonu ve plaka mekanik özelliklerinin incelenmesi
(2022) Saadawı, Hassan A.h.; Konca, Erkan; Tur, Kazım; Metallurgical and Materials Engineering
Son yıllarda, malzemelerin katman katman biriktirilmesi yoluyla ürünler oluşturmak için kullanılan eklemeli imalat (Eİ), çeşitli endüstrilerde üretim süreçlerinin verimliliğini artırmanın bir yolu olarak ilgi konusu olmuştur. Bu tezde, süper dubleks paslanmaz çelik plaka parçalar soğuk metal transferi kaynak tekniği kullanılarak tel ark eklemeli imalat (WAAM) ile elde edilmiştir. İstenen kaynak kalitesini veren eklemeli üretim parametrelerinin (voltaj, akım ve hız) optimum kombinasyonunu elde etmek için, eklemeli kaynak işleminin nümerik simülasyonuna dayalı istatistiksel modeller oluşturmak üzere yanıt yüzeyi yöntemi kullanılmıştır. Deneysel süreci çalışmak üzere COMSOL Multiphysics 5.5 yazılımı ve istatistiksel modelleri elde etmek için Expert-Design yazılımı kullanılmıştır. Kontrol edilen değişkenlerden akım ve gerilim için optimum değerler sırasıyla 200 amper ve 15 volt, kaynak hızı için ise 10 mm/sn olarak bulunmuştur. Daha sonra, sıfır altı sıcaklıklarda tek kenar çentikli çekme (SENT) numuneleri kullanılarak kırılma tokluğu testleri gerçekleştirilmiştir. Kırılma tokluğu verileri, hem haddelenmiş plaka hem de eklemeli imalat ile üretilmiş plaka parçalar için çatlak ilerleme direnci eğrileri oluşturmak ve J-integraline (enerji salım hızı) dayalı sonuçları karşılaştırmak için kullanılmıştır. SDSS Grade 2507 haddelenmiş plaka numuneleri için kararlı çatlak büyümesi başlangıcındaki J-integral değeri (Ji), WAAM DSS Grade 2209'un (Ji) değerinden yaklaşık %17 ve WAAM SDSS Grade 2509'un (Ji) değerinden ise %31 daha yüksek olarak belirlenmiştir.
Termomekanik denetimli haddeleme yöntemi ile API X60 ve X70 sınıfı çelik levha üretimi
(2018) Güneş, Seren; Konca, Erkan; Metallurgical and Materials Engineering
Bu çalışma, API PSL2 X60M ve X70M sınıflarında çelik levha üretimi için haddeleme ve soğutma koşullarını belirlemek üzere bir ön çalışma olarak gerçekleştirilmiştir. Kimyasal kompozisyonları ilgili API spesifikasyonuna uygun 200 mm kalınlığında iki adet tam boy Nb-Ti-V mikroalaşımlı çelik slab, 14 adet küçük slaba dilimlenmiş ve bu slab dilimlerine 20 mm kalınlığında levha üretmek üzere farklı koşullarda termomekanik haddeleme ve hızlandırılmış soğutma işlemleri uygulanmıştır. Özel olarak; i) bitirme haddelemesi sıcaklığı, ii) toplam ezmenin kaba ve bitime haddelemesi arasındaki dağılımı ve iii) duşlu masa kullanarak hızlandırılmış soğutma uygulamanın etkileri çalışılmıştır. Deneme üretimi levhalardan alınan numunelerin mekanik testleri (çekme, darbe ve düşürme ağırlıklı yırtma deneyi-DWTT) ve metalografik incelemeleri gerçekleştirilmiştir. API PSL 2 kapsamında X60 sınıfı çelik levhalar için istenen mekanik özellikleri karşılayan ince taneli ferritik içyapıların tek başına denetimli haddeleme ile üretilebildiği koşullar belirlenmiştir. Öte yandan, API X70 sınıfı çelik levha üretimi için denetimli haddelemeye ek olarak hızlandırılmış soğutmanın da uygulanması gerekmiştir.