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Öğe Austempering Ce-La inoculated solution strengthened ferritic ductile cast irons(Redakcia Kovove Materialy, 2023) Yilmaz, Serdar Osman; Teker, Tanju; Demir, DemetThe influence of austempering conditions on the microstructure, hardness, tensile strength, and impact toughness of Ce-La inoculated solution-strengthened ferritic ductile irons was an-alyzed. The austempering was performed at temperatures 280, 320, 420, 520, and 620 degrees C for periods of 1.5 and 2.5 h. Metallurgical characterization of the samples was determined using scanning electron microscopy, optical microscopy, X-ray diffraction, microhardness, impact, and tensile test. The fracture surfaces of the tensile samples were examined by scanning elec-tron microscopy. Austempering heat treatment significantly enhanced the mechanical charac-teristics of solution-strengthened ferritic ductile cast iron. This led to the birth of solution -strengthened Ce-La inoculated ferritic cast iron, a new spheroidal graphite cast iron family member with a unique microstructure in an ausferritic matrix. Samples austempered for low temperature exhibited higher impact toughness and tensile strength due to the nano-sized ausferrite phase. Austempering for high temperatures displayed higher elongation.Öğe Characterization of mechanically alloyed Fe based and MoNiAl+Al2O3 reinforced composites(Walter De Gruyter Gmbh, 2021) Yılmaz, Serdar Osman; Teker, Tanju; Eker, HüseyincanFe-MoNiAl-Al2O3 powders were mechanically alloyed by a SPEX type attritor. The Fe based composite samples were reinforced with complex mechanically alloyed Fe-MoNiAl-Al2O3 particles in different ratios and Fe matrix composites were obtained. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), elemental surface mapping and microhardness tests were used to analyze the microstructures of the composites. The sintered composites showed that thin Al2O3 particles were dispersed. High volume fractions of the reinforcement having nanometer dimensions were produced in metallic matrices. Additionally, as the content of Al2O3 increased, the microhardness increased, which indicates that fine Al2O3 particles had a reinforcing effect.Öğe Effect of carbides on the wear resistance of white cast iron alloyed with 12.7 wt.-% Cr and nickel(Carl Hanser Verlag, 2020) Yılmaz, Serdar Osman; Teker, TanjuWhite cast iron with about 12.7 wt.-% chromium was alloyed with Ni, W and Mo for heat treatment applications. Heat treatments were performed at a range of 850-1050 degrees C for 1 h in order to distribute M7C3 carbides homogeneously in an environment of high wear resistance. The contents of the C, Cr, Ni, Mo, Mn and Si elements selected for the alloys were similar, though a 6 wt.-% nickel concentration was chosen. Microstructural changes in the specimens were examined by scanning electron microscopy (SEM) and optical microscopy (OM). Macro-hardness, average carbide size and volume fraction were analyzed. Wear tests were carried out under different loads of 10, 20 and 30 N. It was seen that heat treatment changed the carbide size and homogeneous distribution of the carbides. Moreover, the addition of nickel to HCrWCI increased fracture toughness and reduced the wear rate.Öğe Effect of different rotational speeds on mechanical and metallurgical properties of friction welded dissimilar steels(Carl Hanser Verlag, 2018) Teker, Tanju; Yılmaz, Serdar Osman; Karakurt, Eyyüp MuratIn this study, effect of rotational speed on the characteristic microstructure and mechanic properties of the AISI 1030/AISI 420 stainless steel couple welded by friction welding method was experimentally investigated. The weld joints were produced with 1400, 1500, 1600 rpm rotational speed, under 40 MPa process friction pressure and 60 MPa forging pressure for a friction time of 4 s and a forging time of 6 s. After friction welding, the bonding interface microstructures of the samples were examined by scanning electron microscopy (SEM), optical microscopy (OM), energy dispersive spectrometry (EDS) and X-Ray diffraction (XRD) analysis. Furthermore, microhardness and tensile tests were applied to determine the mechanical behavior of weld joints. In addition, fracture types of the tensile test samples were determined from the fractographic examinations by using SEM and EDS. The result of the applied tests and observations pointed out that the mechanical properties and the microstructure changed depending on the increased rotational speed.Öğe Effect of FeTi-FeB inoculation on the shape of carbide reinforcements in hypoeutectic high chromium white cast iron(Walter De Gruyter Gmbh, 2022) Teker, Tanju; Yılmaz, S. Osman; Dalmış, SavaşFeTi-FeB was added to molten high chromium white cast iron in amounts of 0.5-2.5 wt% at 50 degrees C above the melting temperature. The samples were produced in four groups. The first group samples were investigated as cast, the second group homogenized at 1000 degrees C for 1 h, and the other two groups were also homogenized at 1000 degrees C but for 3 and 6 h, respectively. To study the effect of FeB and FeTi on the microstructure, the samples were characterized by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and hardness tests. Wear tests were performed using a pin-on disc. A homogeneously dispersed carbide microstructure was produced by the homogenization heat treatment method. The addition of FeTi-FeB inoculants to high Cr white cast iron played an important role in the distribution of hard carbides. The chemical rate and the carbide volume varied on account of the added hard inoculant particles. TiB2, Cr3C2, M7C3, M23C6, and gamma-FeCr phases formed on the surfaces. The hardness and wear resistance were improved considerably due to FeTi-B inoculation.Öğe Effect of heat treatment on the wear behavior of GX200Cr13Ni6WMoMn(Carl Hanser Verlag, 2019) Teker, Tanju; Dalmış, İbrahim Savaş; Yılmaz, RanaThe effect of cryogenic treatment on the microstructure, hardening behavior and wear resistance of subcritical treated GX200Cr13Ni6WMoMn was investigated. The specimens were improved for thermal shock resistance by having an austenitic matrix in place under all heat treatment conditions. After subcritical treatment, heat treatment increased the hardness and wear resistance of all the specimens since thin secondary carbides precipitated in the rich retained austenite. The amount of precipitated secondary carbides and martensite transformed by cryogenic treatment was greater than by air-cooling. The cryogenic process reduced the amount of austenite, but the austenite retained was not completely converted into secondary carbides. The abrasion resistance, toughness and hardness of the specimens were markedly improved by primary carbides and secondary carbides after heat treatment for 1 h at 900 degrees C.Öğe Effect of mechanical alloying on FeCrC reinforced Ni alloys(Carl Hanser Verlag, 2016) Yılmaz, Serdar Osman; Teker, Tanju; Demir, FatihMechanical alloying (MA) is a powder metallurgy processing technique involving cold welding, fracturing and rewelding of powder particles in a high-energy ball mill. In the present study, the intermetallic matrix composites (IMCs) of Ni-Al reinforced by M7C3 were produced by powder metallurgical routes via solid state reaction of Ni, Al and M7C3 particulates by mechanical alloying processes. Ni, Al and M7C3 powders having 100 mu m were mixed, mechanical alloyed and the compacts were combusted in a furnace. The mechanically alloyed (MAed) powders were investigated by X-ray diffraction (XRD), microhardness measurement, optic microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The presence of the carbides depressed the formation of unwanted NiAl intermetallic phases. The mechanical alloyed M7C3 particles were unstable and decomposed partially within the matrix during alloying and sintering, and the morphology of the composites changed with the dissolution ratio of M7C3 and sintering temperature.Öğe Effect of Ni on microstructure and wear behaviour of 13Cr-W-Mo-2C white cast iron(CSIC Consejo Superior de Investigaciones Cientificas, 2023) Teker, Tanju; Osman Yılmaz, S.The effect of Ni concentration on the microstructure and wear performance of 13Cr-(0.5-7.0) Ni-W-Mo-Mn-2C white cast iron subjected to homogenization heat treatment was examined. Concentration of Ni was altered in the range 0.5-7.0 wt.% to obtain a stable microstructure against for dry sliding wear resistance as long sliding distance. The effect of Ni on the microstructure was analysed by X-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, elemental mapping and hardness. The wear performances were tested under the loads of 40, 90 and 140 N. Differential thermal analysis of samples with dissimilar Ni values was performed. The increase of Ni concentration decreased the secondary arm spacing of dendrites, refined the dendritic structure and raised the eutectic carbide ratio. The greatest wear performance was obtained for the sample having Ni over 6 wt.%. © 2023 CSIC.Öğe Effect of thermomechanical processing on the mechanical properties of CuZn10 alloy(Walter De Gruyter Gmbh, 2022) Yılmaz, S. Osman; Teker, Tanju; Batmaz, Yaşar Onur; Yüksel, ÇağlarThe effects of thermomechanical processing on the grain size, tensile strength, and strain rate of a CuZn10 alloy were investigated. Microstructures of thermomechanically treated samples were introduced using a scanning electron microscope. The relationships between the flow stress, reduction ratio, annealing temperatures, and strain rates were detected for determination of activation energies and optimized thermomechanical parameters. The effect of grain size on the mechanical properties was examined by tensile and microhardness tests. The typical fractographs of samples after tensile tests were examined using a scanning electron microscope. It was observed that the annealing temperature and aging time have significant effects on the optimum grain size. Mechanical properties of the thermomechanically treated samples were improved by strain rate, deformation ratio, annealing temperature, and aging time.Öğe Effect of TiBAl inoculation and heat treatment on microstructure and mechanical properties of hypereutectic high chromium white cast iron(Elsevier Science Sa, 2016) Yılmaz, Serdar Osman; Teker, TanjuHypereutectic high chromium white cast iron alloys were produced with TiBAl (1-3 wt.%) inoculants. The heat treatments were applied to the samples as 1000 degrees C for 1 and 2 h. The microstructures of the samples were investigated by SEM. The chemical concentrations of matrix and carbides were determined by EDS and XRD to detect the type of carbides and matrix. The surface hardness of the samples was detected as HRC. The images of the fracture surfaces of the samples were examined by SEM. The toughness of the samples was evaluated by using charpy V-notch samples to detect the relationship between inoculation, carbide size and fracture toughness. (C) 2016 Elsevier B.V. All rights reserved.Öğe Effect of TiBAl inoculation on abrasive wear resistance of high Cr white cast iron(Carl Hanser Verlag, 2019) Teker, Tanju; Yılmaz, Serdar Osman; Kerkut, ErhanHigh chromium white cast iron (HCrWCI) is generally used in applications requiring superior wear resistance. The alloys were inoculated with 1-3 wt.-% TiBAl to rearrange the crystallography of the carbides. The alloys were subject toheat treatment at 1000 degrees C for 1 and 2 h. The microstructuresof the alloys was examined by SEM. Chemical composition was determined by EDS. For wear tests, alloys were tested using 10, 20 and 30 N loads under pin-on-disc wear conditions. Worn surfaces of the alloys were analyzed by SEM. The worst wear resistance was obtained in the alloy inoculated with 3 wt.-%. TiBAl.Öğe Experimental research on mechanism and process of direct iron making reduction of mechanically milling scale with coal(Elsevier Science Sa, 2015) Yılmaz, Serdar Osman; Teker, TanjuThis study delved into the fundamental mechanisms of a mill scale reduction. To achieve this objective, the DRI process was applied to facilitate the mechanical milling of coal-scale mixtures. Temperatures of 700-1000 degrees C were used to sinter the mechanically milled coal-scale mixtures. The powders were subjected to scanning electron microscopy (SEM) and X-ray diffraction (XRD). In order to identify the reduction of milled scale-coal mixture with the temperature, iron phase analytical techniques and the XRD were used. The differential thermal analysis (DTA) technique was used to determine the measurements of the thermal property. Based on the findings of the experiments, it was concluded that coal devolatilisation and scale reduction forms concurrently when the mixture is being heated. By 40 h milling, the milled coal-scale mixture's reduction start temperature decreased to 750 degrees C. (C) 2015 Elsevier B.V. All rights reserved.Öğe FABRICATION AND PROPERTIES OF FeCrC REINFORCED COPPER ALLOYS BY MECHANICAL ALLOYING(2023) Teker, Tanju; Yılmaz, Serdar OsmanIn this study, properties and fabrication of FeCrC reinforced copper alloys by mechanical alloying were examined using mechanical grinding, optical microscopy, energy dispersive spectroscope, X-ray diffraction, and hardness testing. MA had a very good ability to mix Cu-FeCrC particles. High FeCrC provided more cold work during milling. Thus, smaller crystallite size and greater internal stress occurred in Cu alloys. High performance Cu was further strengthened by a combination of fine grain and alloying. C23C6, Cr7C3 and ?–Cu detected in the structure. The hardness of Cu increased significantly after grinding with FeCrC.Öğe Improved Gx40CrNi25-20 grade austenitic stainless steel(Walter de Gruyter GmbH, 2024) Yilmaz, Serdar Osman; Teker, Tanju; Atik, BahadırIn this study, Ce inoculated GX40CrNi25-20 material was produced by casting. The materials were subjected to heat treatment by being exposed to two different temperatures (1100, 1150 °C) and two different cooling intensities. The effects of heat treatment on primary and secondary carbide concentration, distribution, and type were investigated by using optical microscope, scanning electron microscope, energy dispersive spectrometry, X-ray diffraction, and microhardness tests. The adhesive wear behavior of the materials was determined. After the homogenization heat treatment, the increased cooling intensity application decreased the hardness of the samples. After the homogenization heat treatment, the size of the primary carbides decreased and their distribution became homogeneous. Secondary carbides were dispersed into smaller and equiaxed formin the matrix. EGR inoculating reduced the precipitation of carbides and changed the shape of the precipitate to granule. © 2024 Walter de Gruyter GmbH. All rights reserved.Öğe Investigation on mechanical properties of solution strengthened and austempered ferritic ductile irons(Carl Hanser Verlag, 2020) Yılmaz, Serdar Osman; Teker, TanjuThe aim of this study was to investigate the influence of austempering on the mechanical properties of solution-strengthened ferritic cast ductile irons. The microstructural examinations of the samples were conducted using optical microscopy, scanning electron microscopy, and X-ray diffraction. Hardness, impact, and tensile tests were performed to determine the mechanical features. After the impact test, the fracture surface morphology was analyzed with scanning electron microscopy. The austempering results showed that the matrix structure with 70 % ferrite and 30 % bainite had the highest fracture toughness and yield strength. The ausferrite phase in microstructure played a positive role in ductility, toughness, and strain rates. The mechanical properties were strongly related to the amounts of ausferrite and retained ferrite ratio.Öğe Mechanical properties of Sr inoculated A356 alloy by Taguchi-based gray relational analysis(Walter De Gruyter Gmbh, 2024) Yilmaz, Serdar Osman; Teker, Tanju; Dalmis, Ibrahim Savas; Bulus, ErcanIn this study, Sr inoculated A356 alloy casted by sand-casting technique. Production parameters such as Sr concentration (wt.%), aging temperature (degrees C), aging time (h), and constant cooling rate were used. The effect of heat treatment on the microstructure and mechanical features of inoculated A356 materials was examined by using scanning electron microscopy, optical microscopy, and the Taguchi-based gray relational analysis method. The optimum production parameters for A356 alloy were determined as 0.03 Sr concentration, aging 300 degrees C temperature, and 3 h aging time. Multiple response optimization based on the interaction of these parameters provided a 30.15 % improvement in performance. Gray relational grade (GRG) experimental results showed that the most important parameter was Sr concentration, with a contribution of 76.51 %, according to the analysis by ANOVA statistical method.Öğe Metallurgical characterization of mechanically alloyed MoNiAl-WC reinforced Fe matrix composite(Carl Hanser Verlag, 2020) Teker, Tanju; Yılmaz, Serdar OsmanMoNiAl-WC reinforced Fe matrix composites were obtained by mechanical alloying. The effect of various reinforcement ratios on microstructure change, elemental characterization and phase transformation were examined by using optical microscopy, scanning electron microscopy, energy dispersion spectroscopy, X-ray diffraction, elemental surface mapping and a microhardness test. Fe and MoNiAl-WC compound and powder mixtures were synthesized by MA and nanocrystalline solid solution was obtained. The increase in the reinforcement ratio reduced grain size in the structure and increased the carbide ratio. The composite demonstrated excellent metallurgical qualities and interface bonding. Moreover, it was found that the amount of porosities increased with increasing reinforcement. X-Ray analysis showed the formation of NiAl, Al3Ni and WC phases.Öğe Microstructure and wear analysis of CoWC alloy layers deposited by PTA process(Edp Sciences S A, 2023) Ozabaci, Murat; Teker, Tanju; Yilmaz, S. OsmanCoWC composite coatings were produced on AISI 430 steel by the plasma transfer arc cladding. Three different powder mixtures containing WC (90%, 85% and 80%) and Co (10%, 15% and 20%) were used. Phase composition, microstructural characterization and coating properties were investigated by using scanning electron microscope (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), elemental mapping, hardness and wear test. The wear shape morphology of coatings was determined by SEM. The increased ratio of WC in CoWC powders reduced the degradation of CoWC. The substrate hardness of 180 HV gained a coating hardness value of approximately 462 HV. An increase in the hardness of the coating alloy compared to the substrate was achieved. W2C, WC, CoC and Co6W6C phases were determined on the coating surface. The high levels of WC concentration on the coating surface increased the wear resistance.Öğe MICROSTRUCTURE AND WEAR PROPERTIES OF FeCrC, FeW AND FeTi MODIFIED IRON BASED ALLOY COATING DEPOSITED BY PTA PROCESS ON AISI 430 STEEL(Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2014) Teker, Tanju; Karataş, Selçuk; Yılmaz, Serdar OsmanThe plasma transferred arc (PTA) process was used for developing wear resistance of AISI 430 steel substrate. Appropriate quantities of FeCrC, FeW and FeTi powders were combined to create conditions that synthesized M7C3 particles into reinforced Fe-based composite surface coating. The phase transformations on new created coated surfaces were comprehensively examined by using a combination of scanning electron microscopy (SEM), microanalysis by energy dispersive spectrometry (EDS), X-Ray diffraction (XRD), microhardness and abrasive wear tests. The microstructure studies of the superficial layers of the coating revealed presence of a mixture of the dendritic phase structure of austenite (gamma) and fine eutectic M7C3 carbides. The results show that; the concentrations of the elements (Cr, W, Ti) added as ferroalloys, the size of dendrites formed in the coated surface, the change of hardness of the coated surfaces, the carbide volume rate and thickness of the coating changed by the variation of the processing parameters (ratio of reinforcement particulates and heat input).Öğe Sliding wear behavior of FeCrC reinforced and Ni-based composites produced by mechanical alloying technique(Redakcia Kovove Materialy, 2018) Yılmaz, Serdar Osman; Demir, Fatih; Teker, TanjuThe study presents the behavior of FeCrC particulates reinforced and Ni-based composites produced by a mechanical alloying process in the presence of friction and wear. Ni, Al and M7C3 powders having 100 mu m size were mixed, mechanically alloyed and the compacts were sintered in an atmosphere controlled furnace. The mechanically alloyed (MAed) samples were investigated by SEM, EDS and DTA. For the wear tests, the samples were tested in dry conditions. The worn surfaces were examined using OM to study the wear behavior. The friction coefficient was recorded continuously during the wear test and wear rate. The highest wear rate was obtained at 800 degrees C, and the lowest was obtained at 900 degrees C. With the increase of reinforcement amount, wear rate decreased.
