Sürdürülebilir Kalkınma Amaçları
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- MakaleYalnız künye2026Investigation of the adhesion properties of duplex coating on AZ91 alloy surface by MAO/HiPIMS-PVD methods
Kaplan, Emine Boynueğri; Şüküroğlu, Süleyman; Şüküroğlu, Ebru Emine
This study focuses on enhancing the surface properties and minimizing the mechanical incompatibility between the AZ91 magnesium alloy and the coating by applying CrAlYN/CrYN gradient coatings through the HiPIMS-PVD method, combined with the enlargement of a MgO intermediate layer via the Micro Arc Oxidation (MAO) method. The duplex coating approach was designed to strengthen adhesion and structural integrity between the substrate and the coating. Coating parameters for both MAO and HiPIMS-PVD processes were optimized using a Taguchi L4 orthogonal array, and the coatings were analyzed using SEM, EDS, XRD and scratch testing. MAO coatings exhibited porous and rough surfaces with volcanic morphologies. The best adhesion performance under MAO conditions was achieved with 650 V, 700 Hz, and a Type B solution, resulting in a critical load value of Lc₂ = 24 N. CrAlYN/CrYN gradient coatings alone showed coating thicknesses from 0.83 μm to 1.66 μm with compact and homogeneous microstructures. Adhesive strength was relatively low (Lc₂ = 5–10 N). In the duplex coating configuration, CrAlYN/CrYN coatings were deposited on the MAO-formed MgO layer, significantly increasing adhesion. Critical load values (Lc₂) ranged from 90 to 110 N, with the highest adhesion achieved under low CrY target voltage and current conditions. The findings demonstrate that the MAO/HiPIMS-PVD duplex coating method substantially improves adhesion and surface characteristics of AZ91 alloy, offering a promising solution for advanced surface engineering applications.
- MakaleAçık Erişim2026Experimental and Modeling Study of Fluidity in Ductile Iron (GGG40)
Coşar, Mehmet; Şüküroğlu, Ebru Emine; Güngör, Kadir; Çolak, Murat
Ductile irons (spheroidal graphite cast irons, SGI) are widely used in automotive and energy systems due to their high strength, ductility, and excellent machinability. The casting quality of these alloys largely depends on the flow and filling behavior of the molten metal, namely its fluidity. In this study, the effects of pouring temperature, filling time, and metallurgical quality on the fluidity of GGG40 ductile iron were investigated through both experimental and numerical approaches. Experimental trials were conducted at pouring temperatures of 1350 °C, 1400 °C, and 1450 °C; metallurgical quality levels of 10%, 50%, and 90%; and filling times of 5 s and 10 s. The fluidity lengths were measured and statistically evaluated. The results revealed that increasing the pouring temperature and metallurgical quality significantly improved fluidity, while shorter filling times allowed the molten metal to travel longer distances before solidification. Modeling studies performed using a commercial casting simulation software showed strong correlation with the experimental data. Microstructural examinations indicated that higher pouring temperatures and improved metallurgical quality led to a more homogeneous distribution of graphite nodules and an increased ferrite fraction in the matrix. The findings provide valuable insights into the influence of process parameters on the fluidity behavior of ductile iron and offer critical design data for enhancing casting quality and productivity in industrial foundry applications.
- MakaleAçık Erişim2025Investigation of the Effects of Filling Speed, Casting Temperature and Metallurgical Quality on Fluidity of Lamellar Graphite Cast Iron at Different Section Thicknesses
Köse, Sami; Çolak, Murat; Şüküroğlu, Ebru Emine
In this study, the fluidity properties of the alloy were investigated at different casting temperatures, different section thicknesses, and varying casting parameters of lamellar graphite cast iron materials. To achieve our goal, we utilized sand molds that were created with specific parameters including pouring temperature, metallurgical quality, section thickness, and fluidity test model. These molds were used for casting. Thus, the effect of fluidity properties in changing casting conditions and liquid metal advance distances at determined section thicknesses was investigated. Modeling was carried out with FlowCast casting simulation software by determining the liquid metal advance distance depending on the section thickness in the castings made in sand molds under changing casting conditions. The fluidity and advance distance of the liquid metal was determined comparatively with experimental and modeling techniques under the changing casting conditions in the parameters determined in this study. When the outcomes were examined; it was observed that different liquid metal advance distances occur at different cross-section thicknesses depending on the changing conditions.
- MakaleYalnız künye2025Investigation of structural and adhesion properties of ZnO and h-BN doped TiO2 coatings on Cp–Ti alloy
Belet, Ali Kadir; Şüküroğlu, Süleyman; Şüküroğlu, Ebru Emine
Titanium and its alloys are widely used in aircraft, automotive, chemistry, marine, and military industries owing to their superior properties such as specific strength, very low density, high melting point, high corrosion resistance, good fatigue strength and toughness, low elastic modules, and excellent biocompatibility. However, insufficient tribological properties such as high and unstable friction coefficient, low scraping wear resistance and strong adhesion tendency, and poor corrosion resistance in some aggressive corrosive environments such as severe chloride solution limits the use of titanium and its alloys in some engineering applications. For this reason, it has become quite common to change and/or improve the surface properties of titanium and its alloys. In this study, the structural properties of TiO2 coatings with zinc oxide (ZnO) added TiO2 and hexagonal boron nitride (h-BN) added TiO2 grown composite coatings, respectively, on Cp–Ti substrates by micro-arc oxidation method and the adhesion behavior between the base material and coatings were investigated.
- MakaleAçık Erişim2024Investigation of friction behavior of TiO2: Al2O3 composite coating formed on AA2024 alloy by micro-arc oxidation
Boynueğri̇ Kaplan, Emine; Şüküroğlu, Ebru Emine
In this study, an alumina (Al2O3) ceramic coating and a composite coating containing titanium dioxide (TiO2) particles were prepared on surfaces of AA2024 substrates by micro-arc oxidation (MAO) treatment. The effects of micro-sized (≈20-30 µm) TiO2 particles incorporated into electrolyte on the microstructure, phase and chemical composition, thickness, and friction behavior of the coating were investigated. The surface morphologies of the coatings were analyzed by scanning electron microscopy (SEM). The phase and chemical compositions of the coatings were evaluated by means of X-ray diffraction (XRD) and energy-dispersive X-ray spectrometry (EDS), respectively. The friction coefficient of the coatings was investigated using a pin-on-disc tribometer under condition of dry slip sliding. Moreover, the wear tracks were analyzed by SEM. Addition of TiO2 particles into the electrolyte resulted in the reduction in number of pores and formation of smaller and more uniform pores in comparison with the Al2O3 ceramic coating. XRD analyses demonstrated that the TiO2:Al2O3 composite coating was composed of anatase-TiO2 and rutile-TiO2, as well as pure aluminum, α-Al2O3 and γ-Al2O3 which are the primary phases. The friction tests showed a significant reduction in the friction coefficient of the composite coated samples which contains titanium oxide (TiO2) particles in comparison with Al2O3 coated and uncoated samples. Copyright 2021, Yıldız Technical University.
- MakaleYalnız künye2023The Effect of Surface Roughness on Fatigue Life in AZ31 Magnesium Alloy
Karabudak, Filiz; Şüküroğlu, Ebru Emine; Şüküroğlu, Süleyman; Yeşildal, Ruhi
Magnesium alloys have excellent properties such as high specific strength, rigidity, good damping, electromagnetic shielding, castability, and machinability. However, corrosion, creep, and fatigue resistance are generally the properties that need to be improved. In this study, a hybrid coating was formed on AZ31 magnesium alloy with different surface roughness at different frequencies. In the hybrid coating, an oxide coating was first grown on the surface by the micro-arc oxidation method, and then, the epoxy coating was grown on this oxide coating by the dipping method. The characterization of the coatings was performed by XRD, SEM, and EDS analysis. Furthermore, the relationship between fatigue life and surface roughness was also discussed in this study. The fatigue life and strength of the coated samples were determined as a result of the tests performed on the fatigue device. It was concluded that the fatigue life and strength of hybrid coatings were much better compared to uncoated and single-layer coated samples.
- MakaleYalnız künye2018Differential scanning calorimetry (DSC) and Ni+2 release analysis of NiTi-shape-memory dental alloys coated by micro-arc oxidation (MAO) method
Yeşildal, Ruhi; Karabudak, Filiz; Şüküroğlu, Ebru Emine; Şüküroğlu, Süleyman; Zamanlou, Hamid; Bayındır, Funda; Şen, Sadri; Totik, Yaşar
This study aims to prevent the release of Ni+2 and increase the biocompatibility of NiTi-shape-memory dental alloys with the micro-arc oxidation (MAO) coating by preserving the shape-memory feature in the oral environment. The TiO2-ceramic coating and Ag-doped TiO2 coating have been grown on shape-memory, co-atoms’ dental NiTi alloys with the MAO method. Biocompatibility properties of the coating were determined by in-vitro tests. In-vitro tests have been made as retention tests in a simulated body fluid (SBF). Whether the grown surface coating impacts the shape-memory properties of the base material or not has been determined by differential scanning calorimetry (DSC) analysis. It was observed as a result of retention tests that bone-like apatite form occurred on the surface of TiO2-coated NiTi and Ag-doped TiO2-coated NiTi coating. It was determined as a result of retention tests in SBF that the Ni+2 release rate from the base material was below the limit of detection in coated samples. As a result of DSC analysis, it was not observed any significant changes in transformation temperature with the MAO coating. It was concluded that the thin-film coatings formed by MAO technique prevent the release of Ni in the oral environment and increase the biocompatibility by preserving shape memory properties of NiTi dental alloys.
- MakaleYalnız künye2017An Investigation of Corrosion Resistance and Antibacterial Sensitivity Properties of Nano-Ag-Doped TiO 2 Coating and TiO 2 Coating Grown on NiTi Alloy with the Micro-Arc Oxidation Process
Karabudak, Filiz; Yeşildal, Ruhi; Şüküroğlu, Ebru Emine; Şüküroğlu, Süleyman; Zamanlou, Hamid; Dikbaş, Neslihan; Bayındır, Funda; Şen, Sadri; Totik, Yaşar
In this study, TiO 2 coatings were grown with nano-Ag doped and micro-arc oxidation technique on NiTi shape memory alloy. The antibacterial sensitivity and corrosion resistance characteristics of both coatings were investigated. The microstructure and composition analyses of the coatings were performed with scanning electron microscope, energy dispersive X-ray spectrometry, and X-Ray diffraction (XRD). The XRD results showed that there were only TiO 2 crystal phases (anatase and rutile) on the coating. The results showed that a clean and dense oxide layer was grown on the surface successfully. The surface of nano-Ag-doped TiO 2-coated samples appear to be smoother than the surface of the coatings without Ag. The corrosion tests of the coated and uncoated samples were carried out in three different environments (simulated body fluid, synthetic saliva, and cola) at 37 ∘ which is human body temperature. The corrosion tests showed that the corrosion resistance of TiO 2-coated and nano-Ag-doped TiO 2-coated samples was much higher than the corrosion resistance of the NiTi substrate. Seven different bacteria including (S. aureus, L. monocytogenes, Bacillus subtilis, Salmonella enteritidis, Yersinia enterocolitica, and E. coli, P.aeruginosa) which have the human pathogen feature were used in the antibacterial susceptibility tests. The process was conducted based on the disk diffusion method to test the susceptibility of bacterial strains on the selected coated and uncoated samples, and antimicrobial activity was evaluated in the nano-Ag-doped TiO 2-coated material; P.aeruginosa, Y. enterocolitica, and E. coli (zone diameter of 8–14 mm) were found to be moderately susceptible; S. aureus, L. monocytogenes, B. subtilis, and S. enteritidis (zone diameters of 8–14 mm) were found to be resistant. The antimicrobial activity of the coating material NiTi was found to be sensitive for all antibacterial tests. According to the TiO 2-coated material results, S. aureus, P.aeruginosa, L. monocytogenes, E. coli were found to be moderately sensitive and Y. enterocolitica, S. enteritidis, and B. subtilis were found to be resistant.