Karakaş, Mustafa Serdar
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Doç. Dr.
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Malzeme Bilimi ve Mühendisliği
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Former Staff
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Scholarly Output
7
Articles
12
Citation Count
115
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0
7 results
Scholarly Output Search Results
Now showing 1 - 7 of 7
Article Citation - WoS: 29Citation - Scopus: 30A comparative study on biodegradation and mechanical properties of pressureless infiltrated Ti/Ti6Al4V-Mg composites(Elsevier Science Bv, 2016) Esen, Ziya; Esen, Ziya; Butev, Ezgi; Karakaş, Mustafa Serdar; Karakas, M. Serdar; 52373; 47423; Ortak Dersler Bölümü; Malzeme Bilimi ve MühendisliğiThe mechanical response and biodegradation behavior of pressureless Mg-infiltrated Ti-Mg and Ti6Al4V-Mg composites were investigated by compression and simulated body fluid immersion tests, respectively. Prior porous preforms were surrounded uniformly with magnesium as a result of infiltration and the resultant composites were free of secondary phases and intermetallics. Although the composites' compressive strengths were superior compared to bone, both displayed elastic moduli similar to that of cortical bone and had higher ductility with respect to their starting porous forms. However, Ti-Mg composites were unable to preserve their mechanical stabilities during in-vitro tests such that they fractured in multiple locations within 15 days of immersion. The pressure generated by H-2 due to rapid corrosion of magnesium caused failure of the Ti-Mg composites through sintering necks. On the other hand, the galvanic effect seen in Ti6Al4V-Mg was less severe compared to that of Ti-Mg. The degradation rate of magnesium in Ti6Al4V-Mg was slower, and the composites were observed to be mechanically stable and preserved their integrities over the entire 25-day immersion test. Both composites showed bioinert and biodegradable characteristics during immersion tests and magnesium preferentially corroded leaving porosity behind while Ti/Ti6Al4V remained as a permanent scaffold. The porosity created by degradation of magnesium was refilled by new globular agglomerates. Mg(OH)(2) and CaHPO4 phases were encountered during immersion tests while MgCl2 was detected during only the first 5 days. Both composites were classified as bioactive since the precipitation of CaHPO4 phase is known to be precursor of hydroxyapatite formation, an essential requirement for an artificial material to bond to living bone. (C) 2016 Elsevier Ltd. All rights reserved.Article Citation - WoS: 1Citation - Scopus: 0Effect of nickel content on the boronising behaviour ofpermalloys(Scibulcom Ltd, 2015) Ucar, N.; Karakaş, Mustafa Serdar; Iyi, O.; Calik, A.; Karakas, M. S.; 48915; Malzeme Bilimi ve MühendisliğiPermalloys with nickel contents ranging from 60 to 90% were boronised in a solid medium using the powder pack method. In this method, commercial Ekabor-II powders were thoroughly mixed with ferro-silicon powders to form the boronising medium. The samples were boronised in an electrical resistance furnace for 5 h at 1173 K under atmospheric pressure. The results showed that borosilicide and boride layers were formed on the surface of boronised permalloys, with average hardness of 900-1000 HV0.1. The average thickness of the multilayer coating was 90 mu m, and did not show significant change with Ni content within the range studied. The saw-tooth morphology of the boride layers were smoothened with increasing nickel content.Article Citation - WoS: 7Citation - Scopus: 7A Comparison of Radiation Shielding of Stainless Steel With Different Magnetic Properties(Vinca inst Nuclear Sci, 2014) Calik, Adnan; Karakaş, Mustafa Serdar; Akbunar, Sahin; Ucar, Nazim; Yilmaz, Nihat; Karakas, Mustafa Serdar; Akkurt, Iskender; 48915; Malzeme Bilimi ve MühendisliğiThe radiation shielding properties of three different stainless steels have been investigated. For this purpose, linear attenuation coefficients at photon energy levels of 662 keV and 1250 keV have been measured. The obtained results showed that ferritic stainless steel was more capable in stopping the high energy photons than its non-magnetic counterpart.Article Citation - WoS: 48Citation - Scopus: 51Effect of borotitanizing on microstructure and wear behavior of Inconel 625(Elsevier Science Sa, 2017) Gunen, Ali; Karakaş, Mustafa Serdar; Kanca, Erdogan; Cakir, Huseyin; Karakas, Mustafa Serdar; Gok, Mustafa Sabri; Kucuk, Yilmaz; Demir, Mehmet; 48915; Malzeme Bilimi ve MühendisliğiInconel 625, a nickel-based superalloy, is used in a wide range of applications including the marine and petroleum industries under where it is subjected to harsh conditions such as high temperatures and highly corrosive environments. However, its wear resistance is limited and can be often considered unsatisfactory in some applications. If this alloy were to be used under abrasive wear conditions, its surface would have to be protected by a wear resistant coating. In this study, a two-step thermo-chemical borotitanizing treatment (including an initial boriding step followed by titanium diffusion) is proposed. Microstructural characterization (optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction) and mechanical properties (induding micro-hardness and micro-abrasion wear) of the coated samples were conducted. Microstructural studies revealed a compact, homogenous, silicide-free coating, consisting of four distinct regions: a TiB2 layer, a multi-phase boride layer, a diffusion zone and the substrate. Hardness values were significantly higher than those obtained by standard boriding treatments. Due to the nano-sized bodding agents used, the coatings formed on the surface were thicker than coatings obtained by methods such as nitriding, paste bodding and pack-boriding, and comparable to that of laser boriding. The wear resistance was improved by up to ten times in comparison with untreated Inconel 625. Grooving was the effective wear mechanism in untreated Inconel 625. How-ever the increase in surface hardness achieved by the borotitanizing treatment changed the wear mechanism in the coated samples from grooving to rolling. (C) 2016 Elsevier B.V. All rights reserved.Article Citation - WoS: 25Citation - Scopus: 26Boride Layer Growth Kinetics of Aisi H13 Steel Borided With Nano-Sized Powders(Polska Akad Nauk, Polish Acad Sciences, inst Metall & Mater Sci Pas, 2018) Karakaş, Mustafa Serdar; Karakas, M. S.; Gunen, A.; Yılmaz, Emre; Kanca, E.; Yilmaz, E.; Malzeme Bilimi ve MühendisliğiGrowth kinetics of boride layers in AISI H13 steel was investigated using the pack bonding method at temperatures of 1073, 1173 and 1273 K (800 degrees C, 900 degrees C and 1000 degrees C) for periods of 2, 4 and 6 h with nano-sized boron (NB) and micron-sized Ekabor II powders as bonding agents. The total thickness of the boride layer (including both FeB and Fe2B) after boriding at 1273 K (1000 degrees C) for 6 h was 103.8 gm and 96.5 mu m for the NB and Ekabor II specimens, respectively. X-ray diffraction analysis of the boride layers on the surfaces borided with NB and Ekabor II revealed the presence of FeB and Fe2B phases with sawtooth morphology. The FeB/Fe2B volume ratio was higher in the specimens borided with NB. The thickness of the boride layer (FeB + Fe2B) increased with the increasing boriding temperature and time. The FeB layer in the NB specimen displayed a (002) preferred orientation.Conference Object Citation - WoS: 0Citation - Scopus: 0Diffusion Kinetics of Binary Ti-Ni Shape Memory Alloys(Polish Acad Sciences inst Physics, 2017) Ucar, N.; Karakaş, Mustafa Serdar; Dogan, S.; Ozdemir, A. F.; Karakas, S.; Calik, A.; 48915; Malzeme Bilimi ve MühendisliğiIn this work, the boriding of binary Ti-Ni shape memory alloys was carried out in a solid medium at 1173 and 1273 K for 2, 4, and 8 h using the powder pack method with Ekabor-Ni powders. The boride layer was characterized by optical microscopy and scanning electron microscopy. The obtained results show that boride layer thickness increases with the increasing boriding temperature and time. Depending on temperature and boride layer thickness, the diffusion process is thermally activated, with the mean value of the activation energy being close to 67 kJ/mol.Article Citation - WoS: 1Citation - Scopus: 1Boriding of Binary Ni-Ti Shape Memory Alloys(Walter de Gruyter Gmbh, 2016) Ucar, Nazim; Karakaş, Mustafa Serdar; Dogan, Sule; Karakas, Mustafa Serdar; Calik, Adnan; 48915; Malzeme Bilimi ve MühendisliğiBoriding of binary Ni-Ti shape memory alloys was carried out in a solid medium at 1273 K for 2, 4, 6, and 8 h using the powder pack method with proprietary Ekabor-Ni powders. Characterization of the boride layer formed on the surface of alloys was done by optical microscopy and scanning electron microscopy. The presence of boride, silicide, and borosilicide phases in the boride layers was confirmed by X-ray diffraction analysis. The thickness and microhardness of the boride layers increased with increasing boriding time. Hardness profiles showed a rapid decrease in hardness moving from the boride layer to the main structure. The high hardness of the boride layer was attributed mainly to the formation of TiB2. A parabolic relationship was observed between layer thickness and boriding time, and the growth rate constant for the boriding treatment was calculated as 0.62 x 10(-8) cm(2) s(-1). .
