WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 2Citation - Scopus: 3Use of Combination of Accelerator-Based Ion-Beam Analysis Techniques To the Investigation of the Corrosion Behavior of Cocrmo Alloy(Elsevier Ltd., 2014) Noli, F.; Misaelides, P.; Lagoyannis, A.; Pichon, L.; Öztürk, OrhanNuclear Reaction Analysis - NRA in combination with d-RBS (Ed: 1.35 MeV) was applied in order to investigate the corrosion behavior of CoCrMo alloy. The corrosion resistance of the alloy was compared to that of modified CoCrMo samples by several techniques as plasma nitriding and oxidizing at moderate temperature (∼400 °C). Electrochemical techniques in simulated body fluid 0.9% NaCl (37 °C) were applied in order to accelerate the corrosion process. The nitrogen depth distribution before and after the corrosion was determined using the 14N(d,α)12C and the 14N(d,p)15N nuclear reactions whereas the oxygen by the 16O(d,p)17O. The surface morphology and microstructure was investigated using microscopy techniques. It was found that surface treatments produce thick nitrided layers (5-6 μm) consisting of a supersaturated nitrogen solution (nitrogen concentration is ∼30 at.%) in the matrix (expanded phase γN) and a thin oxygen solution (0.3 μm). The samples subjected to plasma nitridation and oxidation exhibited the lowest deterioration and better resistance to corrosion compared to the single nitrided or single oxidized and the untreated material. This could be attributed to the modified surface region with the high nitrogen content and the presence of oxygen.Article Citation - WoS: 3Citation - Scopus: 4Isothermal Corrosion Testing of Frit Furnace Refractories(Elsevier Ltd., 2009) Balıkoğlu, Fatih; Akkurt, SedatIn this paper, the corrosion behaviour of aluminosilicate type refractories in frit melts is studied in an isothermal corrosion test setup. A refractory brick of largely andalusite and sillimanite composition was compared to another refractory brick of mullite and sillimanite composition, both of which were made by different manufacturers for use in different frit furnaces. The industrial frit used for corrosion tests was a commercial product used in a wall tile glaze formulation. Corrosion tests conducted under isothermal conditions provide quantitative and reproducible data about the corrosion performance of refractories. In this study, tests were performed by partially immersing a 15 mm × 15 mm × 115 mm refractory specimen into a frit melt at temperatures between 1404 and 1504 °C. The effects of temperature, duration of exposure and the refractory brick type were investigated using a statistically designed set of experiments. The ANOVA (analysis of variance) table indicated that temperature and test duration were the most important factor effects, as expected. Increasing both temperature and exposure duration led to an increased amount of corrosion as measured by the cross-sectional area loss of the corroded refractory specimen. Postmortem microstructural analysis was also done on the specimens, with extensive amount of ZnO·Al2O3 precipitation observed along the frit-refractory interface, where crystals of mullite and alumina were also found to precipitate. Increasing the amount of exposure time and temperature produced more ZnO·Al2O3 precipitation. As identified by SEM-EDS analysis, mullite crystals were in the needle-like morphology, while alumina crystals were generally cubic. Additional experiments were conducted by rotating the specimens in the melt at 50 rpm of rotational speed. Due to the reduction of boundary layer thickness, more dissolution was observed from the rotated specimens. In all specimens, corrosion was more pronounced in the bond phase than through the large filler grains of mullite and andalusite.Conference Object Citation - WoS: 4Citation - Scopus: 4Prediction of the Slag Corrosion of Mgo-C Ladle Refractories by the Use of Artificial Neural Networks(Trans Tech Publications, 2004) Akkurt, SedatA multilayer feed-forward back-propagation learning algorithm was employed as an artificial neural network (ANN) tool to create a model to predict the corrosion of MgO-C ladle refractory bricks based on laboratory slag corrosion test data. The corrosion process occurred by immersion of the rectangular refractory specimens in molten slag-steel bath. An ANN model to predict the amount of corrosion was created by using the training data. The model was also tested with experimentally measured data and relatively low error levels were achieved. This model was then used to predict the response of the slag-corrosion system to different values of the factors affecting the corrosion of bricks at high temperatures. Exposure time, exposure temperature of slag-brick contact and CaO/SiO2 ratio of the slag were the factors used for modelling. Model results provided the potential for selection of the best conditions for avoiding the factor combinations that may accelerate corrosion.Article Testing Corrosion Rates on Steel Piping in Geothermal District Heating(National Association of Corrosion Engineers, 2008) İnce, Umut; Toksoy, Macit; Güden, MustafaThe corrosion behavior of St-37 pipeline carbon steel (CS) in a geothermal district heating system was tested at two different fluid velocities. An experimental set-up, directly connected the the end of the transmission line of a geothermal well, was used to assess the corrosion of St-37 steel tensile test coupons prepared in accordance with ASTM E8 in geothermal fluid. The geothermal fluid entered the set-up with a relatively low velocity, 0.02 m/s, and then injected into the well with a relatively high fluid velocity, 9.6 m/s. It was observed that while the uniform corrosion rates were relatively low, pitting corrosion rate, mainly driven by the sulfate-reducing bacteria (SRB) activity, was relatively high and more pronounced at low fluid velocities. St-37 steel material is prone to the pitting type corrosion, thus a biocide chemical addition and the fluid velocity of 2 to 3 m/s in transmission line were recommended to reduce SRB activity to reduce the pitting corrosion rate.