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    Öğe
    An approximation to determine corrosion and mechanical behavior of ti-based alloys
    (World Scientific Publishing, 2021) Yılmaz, Yeşim; Demirören, Hülya
    Titanium and its alloys used in biomaterial applications are preferrably the cause of high-corrosion resistance properties in addition to having good mechanical properties. Commercially pure Ti (CPTi) (Grade 2), Ti6Al4V (Grade 5) and Ti6Al4V-ELI (Grade 23) samples are used as biomaterials exposed to 750 degrees C and 1060 degrees C for 1 h. The samples were cooled in air after heat treatment at 750 degrees C, the other samples were cooled in water after heat treatment at 1060 degrees C. The free-heat treatment samples are as producted. Microstructures of heat-treated samples and non-made samples by comparison were evaluated before and after corrosion process microstructures and tensile strengths. Test solution is 0.5 mol H2SO4 + 1 mol HCl mixture. The corrosion resistance of the titanium samples was evaluated. Microstructure images were monitorized on optical and SEM microscopes. In this paper, the effect of heat treatment was determined on the microstructure, mechanical properties and corrosion resistances of the material. As a result, heat treatment is useful on corrosion resistance of alloyed samples.
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    An electrochemical approach to evaluating surface coatings
    (Inderscience, 2021) Demirören, Hülya; Buytoz, Soner
    In order to understand the influence of metal carbides and niobium carbides on electrochemical behaviour of Fe-based composite powder and FeNb powder coatings were added. Above mentioned composite layer was prepared on a medium carbon steel surface by using GTAW coating technique. The morphology of the coatings' surface was analysed by optical microscope, scanning electron microscope (SEM) equipped with an energy-dispersive spectroscopy (EDS) and X-ray diffractometer (XRD). Then the samples were exposed to seawater. Electrochemical impedance spectroscopy (EIS) method with triple electrode system was used in order to obtain Bode and Nyquist diagrams. Ag/AgCl electrode is used as reference electrode, and platin plate is counter electode in this system. As a result, adding NbC has harmful effect on the electrochemical behaviour of FeCrC coating powder.
  • Küçük Resim
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    An overwiew on corrosion behavior of steels in factory
    (L.N. Gumilyov Eurasian National University, 2021) Demirören, Hülya
    In this study, corrosion behaviors of diffuser unit solution by which raw sugar is produced from minced sugar beets in sugar factories on St-37 low alloy steel and AISI 304, 304L, 316 austenitic stainless steel types were examined. Moreover, influence of heat treatment on corrosion resistance was investigated. Corrosion tests were performed using mass loss method. SEM-EDX, X-rays Diffraction, microhardness and surface hardness analyses of samples were carried out. As a result, it was determined that AISI 304L and 316 steels have better corrosive resistance and heat treatment improves corrosion resistance.
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    Biyomalzeme Olarak Kullanılan Titanyum Alaşımının Elektrokimyasal Sentezi
    (2020) Demirören, Hülya; Yılmaz, Yeşim
    Biyomalzeme uygulamalarında kullanılan titanyum ve alaşımları, iyi mekanik özelliklere sahip olmasının yanı sırayüksek korozyon direnci özelliklerinin nedeni ile tercih edilmektedir. Biyomalzeme olarak kullanılan CP-Ti (Grade 2) veTi6Al4V (Grade 5) numuneler 1 saat boyunca 750 oC'ye maruz bırakıldıktan sonra havada soğutulur. 0,5 mol H2S04 + 1 molHC1 karışık çözeltide analiz edilmiştir. Bu çalışmada bu alaşımların elektrokimyasal davranışları polarizasyon eğrileri eldeedilerek incelenmiştir. Isıl işlem ve alaşımlamanın etkisi elektrokimyasal değerler üzerinde belirlendi. Isıl işlemin vealaşımlamanın titanyumun korozyon direncini artırdığı tespit edilmiştir.
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    CoMoCrSi ile Kaplanmış Ferritik Paslanmaz Çeliğin Korozyon Davranışı
    (2021) Demirören, Hülya; Özel, Serkan
    Ferritik paslanmaz çelikler birçok ortamda korozyona karşı oldukça dayanıklıdır. Bilindiği gibi bu dayanımı artırmanın birkaç farklı yolu vardır. Bunlardan bazıları ısıl işlem, alaşımlandırma, tasarım, inhibitör kullanımı yüzey kaplamalarıdır. Bu çalışmada, ferritik paslanmaz çelik alaşım yüzeyine plazma püskürtme kaplama yöntemi kullanılarak, CoMoCrSi tozu 600 A akım şiddetinde kaplanmıştır. Kaplamasız ve kaplama uygulanan numuneler üçlü elektrot sisteminde korozyon deneylerine tabi tutulmuştur. Tafel eğrilerinden korozyon hızı hesaplanmıştır. Sonuç olarak yapılan kaplamanın ferritik paslanmaz çeliğin korozyon direncini çok iyi artırdığı tespit edilmiştir.
  • Küçük Resim
    Öğe
    Effect of High-Chromium Ferrous-Based TiC Composite Coating on Microstructural and Corrosion Properties of Steels
    (Springer, 2023) Buytoz, Soner; Demirören, Hülya; Kaya, Esad
    Coatings are generally one of the surface protection methods used to prevent corrosion damage. However, coatings with a lean chemical content usually perform low corrosion resistance. Additive carbides could be added to enhance the corrosion resistance of the coatings. Hence, the current study focuses on the effect of TiC addition on FeCrC powder, which is frequently used as a coating material. Different proportions of TiC powder were added to FeCrC powder. 42CrMo4 steel plate was used as substrate. A gas tungsten arc (GTA) welding device was used as the energy source in the coating process. Corrosion tests were performed via a standard three-electrode system. TiC improved the corrosion resistance of FeCrC coating. The corrosion rate was observed to have an inverse proportion of TiC amount in the coating. The sample with the highest TiC powder concentration has the lowest calculated corrosion rate (25 wt %) as 2 × 10–6 (A/mm2).
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    Nadir Toprak Elementleri ve Çeliklerin Korozyonu
    (2021) Demirören, Hülya
    Bilindiği üzere metalik malzemeler için korozyon hayati hasar türlerinden biridir. Yapılan araştırmalarda korozyonun ülkelere olan maliyetinin gayri safi milli hasılanın (GSMH) %3,5-4’ ü kadar olduğu belirlenmiştir. Bu sebeple üstesinden gelmek için çok çeşitli yöntemlere başvurulmaktadır. Bunlar başlangıçta tasarım yani malzeme-ortam uyumunu temin etmek, inhibitör kullanmak, kaplamalar yapmak ve kullanılacak malzemeyi direnci yüksek elementlerle takviye etmektir. İşte bu aşamada test edilen elementler arasında nadir toprak elementleri de önemli yere sahiptir. Nadir toprak elementleri, bildiğimiz şekliyle modern yaşam için çok önemlidir. Nadir toprak elementlerinin kimyası, bu elementlerin korozyon üzerindeki rolünün anlaşılması ve etkili nadir toprak elementi içeren inhibitörlerin hazırlanması için temeldir. Bu çalışmada nadir toprak elementlerinin (NTE) kimyasal özellikleri anlatılarak korozyon özelliklerine ışık tutulmuştur. Daha sonra çelik malzemelerin korozyon özelliklerini nasıl etkilediği incelenmiştir. Çalışmalardan nadir toprak elementlerinin korozyon direnci üzerinde iyileştirici etkiye sahip olduğu belirlenmiştir. Bu iyileştirici etkinin mekanizmaları yapılan çalışmalarla anlatılmıştır. Bu çalışmanın amacı NTE’ nin giderek artan önemine dikkat çekmektir.
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    Optimization of Low-Calorific Coal Application at Different Loads in 600 MW Supercritical Thermal Power Plant with the PROMETHEE-GAIA Method
    (2024) Emir, Aykut; Motorcu, Ali Rıza; Demirören, Hülya
    This study examined the 600 MW supercritical unit of a 1200 MW imported coal-fired thermal power plant in Çanakkale, Türkiye. Coal blends consisting of low-calorific domestic coal (4087 kcal/kg) and high-calorific imported coal (5954 kcal/kg) were combusted at the single mill and burner level to analyze unit parameters at different loads. Initially, input parameters, levels affecting unit parameters, and output parameters influenced by different coal types were identified and prioritized. Using criteria weights determined by the entropy method, the optimal load and domestic-imported coal blend ratio were determined using the Preference Ranking Organization Method for Enrichment Evaluation-Geometrical Analysis for Interactive Aid (PROMETHEE-GAIA) multicriteria decision-making method. The optimization study concluded that a 450 MW load with a 14.6% domestic coal feed rate is the most suitable alternative.
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    The Electrochemical Synthesis of Ferritic Stainless Steel Alloyed With Nb in H2SO4 Environment
    (2020) Demirören, Hülya
    The current paper, the corrosion behaviors of three types stainless steel alloys with particular Nb element rates synthesized to determine the influence of Nb amount. Niobium is stabilizing element for steels. Besides niobium has higher affinity than chromium. So niobium prevents chromium depletion by making niobium carbide. Niobium microalloying is helpful procedure in order to control recrystallization of steel. Niobium microalloying is related on grain refinement. FSS samples were unalloyed and alloyed with 0.5 and 1% Nb samples. Unalloyed sample is referance sample. The specimens are casting and then forging products. Different heat treatments were applied to samples because of homogenization. The samples were exposed the sulphric acid solution. Ferritic stainless steel (FSS) electrodes were analyzed using electrochemical impedance spectroscopy (EIS). The experiments were performed using with three electrodes system at room temperature. The corrosion product morpholgy on the surface tests of specimens was investigated with SEM. SEM micrographs showed that the samples exposed the generalized pitting in the solution. Corrosion rate was accounted by Stearn-Geary equation. It was observed that both niobium alloying and heat treatment for 30 minutes is increased oxidation resistance of ferritic stainless steel to pitting corrosion. The results indicated that niobium reinforced the passif layer.Keywords: Ferritic stainless steel, niobium, corrosion, electrochemical synthesis.