Yazar "Karaoglanli, Abdullah Cahit" seçeneğine göre listele

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    Comparison of calcium-magnesium-alumina-silicate (CMAS) resistance behavior of produced with electron beam physical vapor deposition (EB-PVD) method YSZ and Gd2Zr2O7/YSZ thermal barrier coatings systems
    (Pergamon-Elsevier Science Ltd, 2021) Ozgurluk, Yasin; Karaoglanli, Abdullah Cahit; Ahlatci, Hayrettin
    Thermal Barrier Coatings (TBCs) are generally used in both industrial gas turbines and aircraft engines. In this study, metal powders with CoNiCrAlY content were coated on Inconel 718 nickel-based superalloy substrate materials using the cold gas dynamic spray (CGDS) method, which is a new generation thermal spray coating method. As a top coating, YSZ and Gd2Zr2O7/YSZ (GZO/YSZ), respectively, single and double layer ceramic layers were deposited with an innovative method, physical vapor deposition by electron beam (EB-PVD). All produced TBC systems were sprinkled with vermiculite powder containing CMAS minerals and subjected to CMAS corrosion tests and the effect of CMAS damage on the phase stability and microstructure of TBC systems was determined using elemental mapping analysis, X-ray diffraction (XRD) analysis, and scanning electron microscope (SEM). According to the results obtained, it has been determined that the double layer TBC system with GZO/YSZ is more resistant to CMAS damage than the single layer YSZ system.
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    Cyclic Hot Corrosion Failure Behaviors of EB-PVD TBC Systems in the Presence of Sulfate and Vanadate Molten Salts
    (Mdpi, 2019) Ozgurluk, Yasin; Doleker, Kadir Mert; Ozkan, Dervis; Ahlatci, Hayrettin; Karaoglanli, Abdullah Cahit
    The cold gas dynamic spray (CGDS) method has been considered a promising technology to produce a metallic bond coat for thermal barrier coating (TBC) systems. In this study, CoNiCrAlY bond coats produced by CGDS method were coated with yttria-stabilized zirconia (YSZ) by electron beam physical vapor deposition (EB-PVD). TBCs were subjected to 50 wt % V2O5 and 50 wt % Na2SO4 molten hot corrosion salt combinations at 1000 degrees C. In the case of YSZ top coat on TBCs, the reaction between Na2SO4, V2O5, and Y2O3 salts generates YVO4 crystals, and these structures cause the transformation of tetragonal ZrO2 to monoclinic ZrO2. This situation occurs under operating conditions that lead to TBC failure. Hot corrosion behavior and the related failure mechanisms of TBC systems were investigated and discussed using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, and X-ray diffractometer (XRD).
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    The Effect of Cutting Parameters on Tool Wear During the Milling of Carbon Fiber Reinforced Polymer (CFRP) Composites
    (Kaunas Univ Tech, 2019) Ozkan, Dervis; Gok, Mustafa Sabri; Gokkaya, Hasan; Karaoglanli, Abdullah Cahit
    Reduction of machining times and optimization of cutting parameters and conditions hold great importance in machining processes. Milling is among the most important machining processes used for machining of fiber-reinforced composite materials. The present research was carried out to investigate the effect of cutting parameters on tool wear during the milling of carbon fiber reinforced polymer (CFRP) materials which are widely used in aviation and aerospace industries. A multi-directional CFRP composite material with 6 mm width and 26 layers was used as the workpiece. The tests were performed under dry conditions on a CNC vertical processing center with 100, 200 and 300 m/min cutting speeds; 0.05 , 0.15 and 0.25 mm/tooth feedrates and at 1 mm constant cutting width. To understand the wear process, scanning electron microscopy (SEM) analyses of the worn surfaces were performed.
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    Effect of high temperature oxidation on Inconel 718 and Inconel 718/YSZ/Gd2Zr2O7
    (Iop Publishing Ltd, 2019) Doleker, Kadir Mert; Odabas, Okan; Ozgurluk, Yasin; Askerov, Hangardas; Karaoglanli, Abdullah Cahit
    Oxidation is an important phenomenon for materials used at high temperatures. Generally, nickel based superalloys are preferred as metallic materials due to their superior mechanical properties for high temperature applications. Inconel 718 has wide usage fields in high temperature applications. In present study, Inconel 718 and Inconel 718/Yttria (%8 Y2O3) Stabilized Zirconia (YSZ)/ Gd2Zr2O7 (GZ) was oxidized in open air atmosphere at 1000 degrees C for 8, 24 and 100 h. Isothermally oxidized samples were investigated using Scanning Electron Microscopy (SEM), x-ray Diffraction (XRD) and energy dispersive x-ray spectrometry (EDX)-SEM. Results show that Inconel 718 is not suitable for long periods at 1000 degrees C. Ceramic coated Inconel 718 exhibit better performance and it assist to see phase distributions in microstructure.
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    Evaluation of oxidation and thermal cyclic behavior of YSZ, Gd2Zr2O7 and YSZ/Gd2Zr2O7 TBCs
    (Elsevier Science Sa, 2019) Doleker, Kadir Mert; Ozgurluk, Yasin; Ahlatci, Hayrettin; Karaoglanli, Abdullah Cahit
    Thermal barrier coatings (TBCs) are widely used to increase gas turbine efficiency and to prolong the lifetimes of superalloy substrates. Yttria (7-8%) stabilized zirconia (YSZ) is used as a state of the art TBC top coating material. In recent years, rare earth zirconates have drawn interest as top coating materials due to their high phase transformation temperature and low thermal conductivity. In the present research, CoNiCrAlY powders were sprayed on Inconel 718 superalloy substrates using high velocity oxy fuel (HVOF) deposition technique. YSZ, Gd2Zr2O7 (GZ) and YSZ/GZ top coats were then deposited on the resulting bond coat using EB-PVD technique. The produced TBCs were exposed to isothermal oxidation at 1100 degrees C for 4 different periods, and furnace thermal cyclic tests were conducted at 1150 degrees C. After thermal loadings, TGO (thermally grown oxide) growth behavior and crack surfaces of TBCs were evaluated. Samples were compared with each other using analysis techniques like scanning electron microscopy (SEM), energy dispersive sprectrum (EDS) elemental mapping and X-ray diffraction (XRD) before and after the oxidation tests. The results showed that double layered TBC system is more durable against high temperature degradations.
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    Influence of Sn addition on microstructure and corrosion resistance of AS21 magnesium alloy
    (Elsevier, 2019) Zengin, Huseyin; Turen, Yunus; Ahlatci, Hayrettin; Sun, Yavuz; Karaoglanli, Abdullah Cahit
    This study aims to investigate the influence of Sn addition on microstructure and corrosion properties of AS21 magnesium alloys. The AS21 alloys with 0, 0.5, 1 and 2 wt.% Sn additions were produced by low pressure die casting method. Microstructure characterizations were performed by optical and scanning electron microscopy. Corrosion properties of the alloys were examined by immersion and electrochemical corrosion tests in 3.5% NaCl solution. The microscopic results showed that AS21 alloy consisted of alpha-Mg, isolated beta-Mg17Al12 and Chinese script type Mg2Si intermetallic phases. With increasing amount of Sn, the distribution of Mg2Si phase became more discrete and denser. After 2 wt.% Sn addition, a Sn-rich network structure formed throughout the microstructure and islands of Chinese script shape were made of shorter rods of Mg2Si phase. The constant immersion corrosion tests revealed that increasing Sn addition led to a continual decrease in the degradation of AS21 alloys, in which the corrosion rate of AS21 alloy was decreased by approximately 65% with 2 wt.% Sn addition. The electrochemical corrosion tests also showed that the corrosion resistance of AS21 alloy was gradually improved with increasing Sn content.
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    Investigation of calcium-magnesium-alumino-silicate (CMAS) resistance and hot corrosion behavior of YSZ and La2Zr2O7/YSZ thermal barrier coatings (TBCs) produced with CGDS method
    (Elsevier Science Sa, 2021) Ozgurluk, Yasin; Doleker, Kadir Mert; Ahlatci, Hayrettin; Karaoglanli, Abdullah Cahit
    Thermal barrier coatings (TBCs) commonly expose to oxidation, hot corrosion, and CaO-MgO-Al2O3-SiO2 (CMAS) attacks during the service condition. All of these attacks cause the spallation or delamination of TBCs from the bond coat. In this study, the effect of these attacks on YSZ and La2Zr2O7/YSZ TBC systems was investigated. YSZ and double layer La2Zr2O7/YSZ topcoats were deposited using electron beam physical technique (EB-PVD) on CoNiCrAlY bond coat produced by cold gas dynamic spray (CGDS) technique. CMAS tests at 1225 degrees C for 4, 8, 12, 16, 20, 24, 28, and 32 h and 5 h cyclic hot corrosion tests at 1000 degrees C were carried out on TBCs. Before and after the tests, TBCs were characterized using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), x-ray diffraction (XRD) and image analysis software program. At the end of the tests, the formed phases, microstructural changes, and general failure mechanisms were investigated in detail for each test. The general result shows that double-layered TBCs provide significant contributions and durability against high-temperature corrosive attacks of conventional YSZ TBC. In addition, in this study, hot corrosion damage mechanism and CMAS attack significantly damaged the column morphology of the EB-PVD method, reducing the thermal insulation properties and strain tolerance of TBCs. As a result of the tests, spallation and phase changes occurred in the damaged TBC systems.
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    Investigation of hot corrosion behavior of thermal barrier coating (TBC) systems with rare earth contents
    (Springer Heidelberg, 2018) Ozgurluk, Yasin; Doleker, Kadir Mert; Ahlatci, Hayrettin; Karaoglanli, Abdullah Cahit
    Thermal barrier coatings (TBCs) are extensively used to protect critical components such as aircraft turbines to provide thermal insulation at elevated temperatures. At high operating temperatures, damage mechanisms such as oxidation and hot corrosion result in spallation of TBC system. The spallation occurs due to the phase transformation during penetration of hot corrosion salts to top coat. YSZ is mainly used as top coat material for TBC systems. However, YSZ cannot be used in temperature higher than 1000 A degrees C. More superior efficiency of gas turbine engines will demand a new generation materials for TBC systems. Nowadays, rare earth zirconates, Gd2Zr2O7, La2Zr2O7, YSZ/Gd2Zr2O7, and YSZ/La2Zr2O7 used as ceramic top coat materials in gas turbine engine components owing to their superior thermal isolation and hot corrosion resistance properties. In this study, hot corrosion mechanism, rare earth zirconates, and their properties as well as their hot corrosion behavior in TBCs were investigated based on literature studies.
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    Investigation of Isothermal Oxidation Behavior of Thermal Barrier Coatings (TBCs) Consisting of YSZ and Multilayered YSZ/Gd2Zr2O7 Ceramic Layers
    (Springer/Plenum Publishers, 2017) Doleker, Kadir Mert; Ahlatci, Hayrettin; Karaoglanli, Abdullah Cahit
    Rare-earth zirconates have a big potential as top coat material of TBCs due to their superior high-temperature properties. TBCs are usually produced by thermal spray methods or electron beam physical vapor deposition (EB-PVD) techniques. Cold gas dynamic spray (CGDS) is a promising deposition method for production of dense and non-oxide bond coat compared to other thermal spray processes, while EB-PVD process provides good adhesion and strain tolerance for top coating layers of TBCs. In this study, in order to observe the effect of Gd2Zr2O7 on the oxidation behavior of TBCs, CoNiCrAlY was sprayed on substrate material using the CGDS method, afterward, yttria-stabilized zirconia (YSZ) and YSZ/Gd2Zr2O7 were deposited using EB-PVD technique. After deposition, specimens were isothermally oxidized in a high-temperature furnace at 1100 A degrees C for 8, 24, 50, and 100 h. Microstructures of oxidized samples were examined and thermally grown oxide layer of TBCs were comparatively evaluated.
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    Isothermal Oxidation Behavior of Gadolinium Zirconate (Gd2Zr2O7) Thermal Barrier Coatings (TBCs) produced by Electron Beam Physical Vapor Deposition (EB-PVD) technique
    (De Gruyter Poland Sp Zoo, 2018) Doleker, Kadir Mert; Ozgurluk, Yasin; Ahlatci, Hayrettin; Karaoglanli, Abdullah Cahit
    Thermal Barrier Coatings (TBCs) provide thermal insulation for gas turbine components operating at high temperatures. Generally, TBCs were produced on a MCrA1Y bond coat with 7-8% Yttria Stabilized Zirconia (YSZ) using Atmospheric Plasma Spray (APS) technique. In this study, Inconel 718 substrate material was coated with CoNiCrAlY bond coat using high velocity oxygen fuel (HVOF) technique. Afterward, Gd2Zr2O7 was deposited on samples using Electron Beam Physical Vapor Deposition (EB-PVD) technique. Produced TBCs were exposed to isothermal oxidation tests at 1000 degrees C for 8 h, 24 h, 50 h and 100 h in muffle furnace. Scanning electron microscopy energy distribution X-ray (SEM-EDX) spectroscopy was used to investigate thermally grown oxide (TGO) layer and TGO growth behavior of TBCs. In addition, X-ray Diffractometer (XRD) analysis was performed to TBCs to understand whether phase transformation occurs or not before and after oxidation.
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    Machining effects on delamination failure in milling MD-CFRPs with uncoated carbide tools
    (Ice Publishing, 2019) Ozkan, Dervis; Gok, Mustafa Sabri; Gokkaya, Hasan; Karaoglanli, Abdullah Cahit
    As one of the main failure mechanisms emerging in the milling of carbon (C)-fiber-reinforced polymer (CFRP) materials, delamination is primarily affected by cutting tool material and geometry, machining parameters and the dynamic loads arising during the machining process. In this study, machinability tests were performed without the use of coolants to examine the effect of machining parameters on multidirectional CFRP composite workpieces, which have a wide application in industries. The tests were applied on a computer numerically controlled vertical processing center at three different cutting speeds (100, 200 and 300 m/min), three different feed rates (0.05, 0.15 and 0.25 mm/tooth) and constant cutting depth (1 mm). Following the tests, the changes in the workpiece were examined in terms of surface roughness, cutting forces, tool wear and delamination failures. The average surface roughness increased with increasing feed rate. Cutting forces also increased with increasing cutting speed, which caused improvements on average surface roughness values. As a machining parameter, feed rate was found to be a determining factor in the machining of CFRP composite materials.
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    The Microstructural Investigation of Vermiculite-Infiltrated Electron Beam Physical Vapor Deposition Thermal Barrier Coatings
    (De Gruyter Poland Sp Zoo, 2018) Ozgurluk, Yasin; Doleker, Kadir Mert; Ahlatci, Hayrettin; Ozkan, Dervis; Karaoglanli, Abdullah Cahit
    Thermal barrier coatings (TBCs) are widely used in aerospace and aviation industries for materials required to withstand severe environments such as oxidation, hot-corrosion failure and CMAS (calcia-magnesia-alumina-silica) attack or vermiculite corrosion. This is particularly apparent in vermiculite, which can penetrate sand, volcanic ash and is the most destructive damage mechanism in the TBC system. Impurities from the desert environment such as calcia-magnesia-alumina-silica (CMAS) cause degradation of TBCs. In this research, CoNiCrAlY metallic bond coatings were deposited on Inconel 718 nickel based superalloy substrates with a thickness of around 100 mu m using a Cold Gas Dynamic Spray (CGDS) technique. Production of TBCs were carried out with deposition of YSZ ceramic top coating material using Electron Beam Physical Vapor Deposition (EB-PVD), with a thickness of around 200 mu m. The effect of CMAS with spreading naturally-occurring mineral (vermiculite) on TBC samples were investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) analysis and X-ray diffraction (XRD). The microstructure evolution of YSZ and failure mechanism of TBC were evaluated.
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    An Overview of Utilization of Blast Furnace and Steelmaking Slag in Various Applications
    (Elsevier Science Bv, 2019) Oge, Mecit; Ozkan, Dervis; Celik, M. Bahattin; Gok, Mustafa Sabri; Karaoglanli, Abdullah Cahit
    Ever-increasing energy costs and environmental restrictions have compelled researchers to focus on the reutilization of vast amounts of industrial by-products such as blast furnace slag and steelmaking slag, in energy extensive and material extensive industries such as iron-steel production and construction. Attempts to reutilize these waste materials all around the world have yielded successful results up to date, such that, in some of these attempts they even surpassed their intended use as blend or replacement materials and became serious rivals to their industrial counterparts. Various ways to reutilize these waste materials have been explored up to date, including waste heat recovery, clinker substitute in cement production, and a number of comparatively more value added applications. The ongoing attempts have come to a point that pushes the limits for more technological uses such as alternative ceramic coating materials in surface engineering applications. In this regard, this review study aims to provide an overview of and a collective approach to various uses of blast furnace and steelmaking slag in diverse applications and fields, with a view to provide insight into the current attempts to optimize or improve their use, as well as emerging trends as to the potential use of these waste materials in higher value-added applications. (c) 2019 Elsevier Ltd. All rights reserved.
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    Oxidation Behavior of NiCr/YSZ Thermal Barrier Coatings (TBCs)
    (De Gruyter Poland Sp Zoo, 2018) Doleker, Kadir Mert; Ozgurluk, Yasin; Parlakyigit, Abdullah Selim; Ozkan, Dervis; Gulmez, Turgut; Karaoglanli, Abdullah Cahit
    Nichrome (NiCr) coatings are widely used to provide resistance against oxidation and corrosion in many machine components. TBCs must include bond coatings that are resistant to oxidation resulting from high-temperature operating conditions. In the present study, NiCr powders were sprayed on nickel-based superalloy Inconel 718 substrates using atmospheric plasma spray (APS) technique. Bond-coated substrates were coated with yittria stabilized zirconia (YSZ). As such, the TBC samples were kept at 1000 degrees C for 8 h, 24 h and 50 h in high temperature furnace and their isothermal oxidation behavior was investigated. Microstructure and phase change properties of TBCs before and after isothermal oxidation were then studied and analyzed.