MCBÜ Açıkerişim Sistemi :: Browsing by Author "Gül, C"

Browsing by Author "Gül, C"

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Improvement in Corrosion Resistance of Tantalum Oxide and Tantalum Oxide with Diethanolamine Sol-Gel Coated Magnesium Alloys
Gül, C; Albayrak, S; Çinici, H; Aytaç, A
In this study, corrosion resistance was developed to ensure that AZ91 Mg alloy remains stable in the body for longer periods. For this purpose, tantalum oxide and tantalum oxide with diethanolamine coatings were made by sol-gel method on AZ91 magnesium alloy surfaces. The structural analyses of tantalum oxide and tantalum oxide with diethanolamine obtained by sol-gel method were carried out. By using the dip coating method, coatings with different concentrations of solutions and different dipping numbers were applied on AZ91 Mg alloy surfaces. Thus, the effects of dipping numbers and chemical content of the solution on the coating thicknesses, surface roughnesses, morphologies and corrosion resistances of coating layers were examined. As a result, it was determined that the coating thicknesses increased with the dipping number. The low number of dipping could not provide sufficient protective layer formation on the surface. Better results were obtained in samples with a high dipping numbers. It was observed that needle-like structures were formed in the solution using diethanolamine. As the amount of diethanolamine increased, a more homogeneous and dense coating layer was observed. Accordingly, an increase in corrosion resistance has been observed. It was determined that the corrosion rate of AZ91 Mg alloy has decreased by 86% with increasing dipping number and diethanolamine amount.
Improving the wear resistance of the magnesium alloy WE43 by cold sprayed Ni-Al2O3 and Ni-Zn-Al2O3 coatings
Gül, S; Durmus, H; Gül, C; Çömez, N
Lightweight magnesium (Mg) alloys are employed in a wide range of applications due to their high specific strengths. Nevertheless, some applications require improvement of the wear resistance of Mg alloys. The purpose of this study was to investigate the effect of the initial surface conditions, cold spray temperature, and coating material on the wear resistance of the cold sprayed coatings on WE43 Mg substrate. Blasted and sandpapered surfaces were coated with commercial powders of K-32 (Ni and Al2O3) and K-714 (Zn, Ni, and Al2O3). The coating materials were cold sprayed on blasted and sandpapered WE43 Mg surfaces at 500 ?and 600 ?. Surface roughness, thickness and wear resistance of the coatings were examined. Deposition efficiency was improved by raising the N-2 gas temperature. The samples with the greatest wear resistance were those that were coated with Zn, Ni, and Al2O3 powder mixture on sandpapered surfaces at temperatures of 600 ?, where deposition efficiency is maximum. Cold spray coatings enhanced the wear resistance of the WE43 Mg substrate.
Characterization of Tantalum Oxide Sol-Gel-coated AZ91 Mg Alloys
Gül, C; Albayrak, S; Çinici, H
Synthesis of tantalum oxide (Ta2O5) powders via sol-gel method and Ta2O5 coating ability onto AZ91 Mg alloy were investigated, in this study. AZ91 Mg alloy was chosen as substrate because of its low density and similar mechanical properties to bone. However, some surface treatments are needed, because the Mg alloy cannot maintain its mechanical integrity in the biological environment for long periods of time. Ta2O5 is a promising coating layer for biomedical applications, because of its excellent corrosion and wear resistance and biocompatibility. In the case of Ta2O5 coatings applied on AZ91 Mg alloy, which is advantageous in many respects, it can be used in long-term applications within the body. The novel study aims for the characterization of Ta2O5-coated AZ91 Mg alloys. AZ91 Mg alloy samples were produced using a powder metallurgy method. The Ta2O5 solution was prepared by sol-gel method. The prepared solution was used for both powder producing and coating processes. For the powder producing process, the solution was aged, dried and sintered sequentially. Then, Ta2O5 powders were obtained. For the coating process, the solution was applied to the AZ91 Mg alloy samples' surfaces using a dip coater. Coated samples were dried and sintered. The morphologies of the samples were investigated by using scanning electron microscope with energy-dispersive spectroscopy (SEM-EDS, Jeol JSM 6060 LV) and X-ray diffraction (XRD, Bruker D8 Advance). The dried Ta2O5 powders were analyzed using combined thermogravimetry-differential thermal analysis (TG-DTA, Hitachi STA 7300). The coating ability of the tantalum oxide layer on the AZ91 Mg alloy surface has been discussed. The results demonstrate that an optimum amount of deflocculating chemicals must be added to the coating in order to optimize the surface morphology. [GRAPHICS] .
Effect of Dipping Number on Morphology of Ta2O5 Coatings Made by Sol-Gel Method on AZ91 Mg Alloy
Gül, C; Albayrak, S; Çinici, H
The study involves the characterization of the Ta2O5 coated AZ91 Magnesium (Mg) alloys produced using the sol-gel method. Mg alloys have a serious potential for use in orthopedic applications due to their lightness and mechanical properties close to the mechanical properties of human bone. However, their corrosion resistance is insufficient for long-term use within the body. Tantalum (Ta), on the other hand, is an element with a high corrosion resistance and does not create a toxic effect on the body thanks to the oxide layer formed on its surface. In this study, it was aimed to cover Ta2O5 in different dipping numbers with the sol-gel method on AZ91 Mg alloys produced by powder metallurgy method and to investigate the effect of this change on the morphology of the coatings. After the samples were coated in different dipping numbers, the change in their morphology was examined using electron microscopy (SEM-EDS) and X-ray diffraction (XRD). As a result of the study, it was observed that the distance between the islets was shortened in the cracked structures encountered in the sol-gel method. With the increasing number of dipping, samples with an average coating thickness of 1, 3 and 7 mu m were produced and a more homogeneous coating structure was created on the surface.
Validation of the Turkish Form of Short Form-12 health survey version 2 (SF-12v2)
Gündüz, ÖS; Mutlu, S; Basli, AA; Gül, C; Akgül, Ö; Yilmaz, E; Aydemir, Ö
Objectives: In this present study, we aimed to perform the reliability and validity analyses of the Turkish Form of Short Form-12 version 2 (SF-12v2) in different groups of patients. Patients and methods: After the permission for the validation study of the Turkish Form, Optum provided the authors the validly translated Turkish Form of SF-12v2. The study was carried out in rheumatological, psychiatric, and surgical wards of Manisa Celal Bayar University Hafsa Sultan Training and Research Center between September 2019 and June 2020. Taking possible dropouts into consideration, a total of 136 patients (67 males, 69 females; mean age: 43.5 +/- 14.4 years; range 19 to 82 years) constituted the study group. In addition to SF-12v2, for concurrent validity, Nottingham Health Profile (NHP) was used as the comparator instrument. Results: In internal consistency, for the physical component summary score, the Cronbach alpha coefficient was 0.80, and item-total score correlation coefficients were between 0.32 and 0.73. The Cronbach alpha coefficient of the mental component summary score was found to be 0.88 where the item-total correlation coefficients varied between 0.60 and 0.78. Exploratory factor analysis revealed a two-factor solution, representing mental and physical components. For criterion validity, convergent and discriminant validity analyses were performed using NHP with SF-12v2, and domains of SF-12v2 correlated well with the domains of NHP accordingly. In criterion validity, the psychiatric group had the lowest mean score in mental health, vitality, social functioning and role difficulties due to emotional problems, whereas the surgical group had the lowest mean score in bodily pain, role difficulties due to physical problems, and physical functioning. Conclusion: Our study results show that the Turkish form of SF-12v2 is valid and reliable both in clinical practice and clinical trials.
The effects of alkali, alkali-acid and sandblasting surface treatments applied before Tantalum-Oxide coating with magnetron sputtering on the wear behavior of 7075 Aluminum alloys
Gül, C; Albayrak, S; Çinici, H; Simsek, IBA
Aluminum alloys are alloys that are widely used in many sectors due to their high specific strength and are constantly being developed to adapt to today's developing technology. Among these alloy groups, the use of 2XXX and 7XXX series alloys, which are alloy groups that can be hardened by precipitation hardening, is even more common. In this study, an amorphous tantalum-oxide layer was coated by magnetron sputtering method in order to improve the wear resistance of 7075 aluminum alloys. It was applied to the sample groups after polished, sandblasted, alkali, and alkali acid treatments, and the effect of the surface treatments applied before coating on the wear performances after coating was investigated. The effect on the surface morphologies after coating was investigated using scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS), and their structural analysis was investigated by the X-ray diffraction (XRD) method. The wear behavior of the samples was determined by the ball-on disc wear test performed at room temperature under dry sliding conditions and by SEM examinations, wear track profile measurements, average volume loss calculations and friction coefficient evaluations performed after wear. After the coating process, Ta2O5 coating was obtained in an amorphous structure without cracks, voids, and heterogeneity. Coating thicknesses were measured as approximately equal to 2.5-5 mu m. The highest wear resistance among all samples was observed in the samples coated after alkali and alkali acid treatments, and it was observed that the volume losses after wear decreased by 69-77% compared to the polished and untreated sample.
Effect of sandblasting and aging on structural and mechanical properties of Inconel 625 coated steels for marine applications
Durmus, H; Çömez, N; Gül, C
In present study, the Inconel 625 alloy was coated using TIG welding method, and the coating was subjected to sandblasting and artificial aging. The coating samples were examined by wear and corrosion tests to evaluate their performance in marine applications. The study characterized different sample groups for the purposes of coating steel samples, coating surfaces by deformation, applying aging processes, and observing the combined effects of aging and deformation. Wet-sliding wear and corrosion tests were conducted in 3.5 wt.% NaCl solution. The presence of compressive stresses resulting from sandblasting and aging led to microstructural changes, while formation of delta, gamma ', gamma '' phases and complex carbides contributed to increased wear and corrosion resistance. Deformation supported the precipitation of gamma ', gamma '' phases and carbides. Aging increased the hardness by 30 %, whereas the sandblasting process doubled up the hardness of as-deposited coating. Maximum corrosion resistance was obtained in the aged sample without applying sandblasting.
Wear and corrosion resistance of zinc-oxide and zirconium-oxide coated WE43 magnesium alloy
Gül, C; Durmus, H; Albayrak, S; Çömez, N
Magnesium alloy, which draws attention with its lightness and high specific strength, is frequently preferred due to its advantages. However, it is necessary to improve the wear and corrosion properties in order to develop the areas of use in the automotive, aircraft, and space industries. For this purpose, after the surface preparation of the main material WE43 Mg alloy, ZnO and ZrO2 coatings were made and characterized in this study. The surface morphology and structural and chemical properties of the samples were investigated using profilometry, contact angle tests, scanning electron microscopy, and x-ray diffraction. Corrosion tests have been carried out. In order to determine the wear performance of the samples, the wear-related volume losses were measured and the friction coefficients were compared. Layers with 2-6 mu m coating thickness were obtained homogeneously on the polished and sandblasted sample surfaces. It was determined that the coating layers grew in the form of columns and did not contain capillary cracks. As a result of the study, it was observed that the ZnO-coated samples had the highest wear and corrosion resistance, and the wear and corrosion resistance of the coatings and magnesium alloy substrates improved.
Fe-Cr-C-V hardfacing coatings with molybdenum addition: Wear, corrosion, and cavitation performances
Çömez, N; Yurddaskal, M; Gül, C; Durmus, H; Albayrak, S
The purpose of this study was to determine how molybdenum content affected the hardfacing coatings made of Fe-Cr-C-V that resist wear, corrosion, and cavitation. The hardfacing process was applied on the S235JR steel by the metal arc welding method. Apart from the chromium-rich M23C6 and M7C3 (M: Cr, Fe) carbides, the presence of molybdenum led to the development of M2C (M: Mo, Fe, Cr) carbides. As molybdenum and carbon concentration decreased, the size and volume fraction of M23C6 and M7C3 carbides tended to reduce. While molybdenum did not significantly alter hardness or wear resistance, it was found to be advantageous in terms of cavitation and corrosion. The coating, including 3 wt% FeMo, demonstrated a 20-fold increase in cavitation resistance compared to the coating devoid of molybdenum. The hardfacing coatings' resistance to corrosion was increased by up to 4.5 times with the addition of molybdenum.
Electrochemical, mechanical, and antibacterial properties of the AZ91 Mg alloy by hybrid and layered hydroxyapatite and tantalum oxide sol-gel coating
Albayrak, S; Gül, C; Emin, N; Gökmen, U; Karakoç, H; Uzun, A; Çinici, H
The corrosion and bacterial behavior of AZ91 magnesium alloy coated with sol-gel-deposited amorphous tantalum oxide and hydroxyapatite have been investigated. The objective was to assess the potential suitability of AZ91 for permanent prosthesis applications. The coatings were applied in layered and hybrid configurations and characterized using various techniques including X-ray diffractometry, Fourier transform infrared spectroscopy, scanning electron microscopy/energy dispersive spectrometry, and drop analyses. The antibacterial properties were evaluated through interactions with Staphylococcus aureus and Escherichia coli strains. Mechanical properties and adhesion were determined via linear scratch tests, and electro-chemical corrosion tests were conducted in different media. The release of aluminum ions from the samples in Dulbec-co's Modified Eagle's Medium was monitored over 28 days. The findings revealed that the amorphous tantalum oxide coating, particularly in combination with hydroxyapatite, improved antibacterial properties and positively influenced corrosion and scratch resistance. The layered and hybrid coatings demonstrated the highest corrosion resistance. The release of aluminum ions remained within acceptable levels in the tested medium. Overall, the study provides valuable insights into the potential of sol-gel coatings on AZ91 for prosthetic applications, considering antibacterial behavior, corrosion resistance, and aluminum release.
Wear performance of Fe-Cr-C-B hardfacing coatings: Dry sand/rubber wheel test and ball-on-disc test
Durmus, H; Çömez, N; Gül, C; Yurddaskal, M; Yurddaskal, M
Minimizing wear would ensure reduced loss of material, labor and time for numerous branches of industry. Hardfacing coating method is a promising application to overcome this loss. The purpose of the the hardfacing application is to support, repair or improve the surface that is susceptible to abrasion by forming hard phases. The present study was aimed to investigate the wear resistance of iron-based hardfacing coatings which were produced with Fe-Cr-C-B and Fe-Cr-C based filler wires, according to ball-on-disc and dry sand rubber wheel wear tests. During the open arc welding process powder compositions of 100% FeB and 40% FeB + 60% FeCr were transferred to the weld pool, in order to enrich the coating with boron and chromium. Increased FeB content ensured the formation of boride phases such as Fe2B, CrB2, B6Fe23, Cr5B3. Minimum wear loss was obtained in a sample which was coated with Fe-Cr-C-B based filler wire reinforced with 40% FeB + 60% FeCr powder. Formation of massive carbide/boride phases and a tough matrix protected by the high amount of secondary carbides increased the wear resistance. The outcomes showed that the wear resistance is not only correlated with hardness but also affected by the morphology of microstructural constituents.
Al/Zn/Al2O3 and Zn/Al2O3 Coatings by Cold Spray Coating Method of WE43 Magnesium Alloy and Investigation of Its Wear Behaviors
Gül, C; Albayrak, S; Çömez, N; Durmus, H
Mg alloys are preferred in automotive, aircraft, aerospace and communication industries due to their low specific gravity and high strength. WE series is a series of Mg alloys containing Mg, Y, Nd, rare earth elements, and although the creep strength is good for this alloy series, the wear resistance is open to improvement. The aim of this study is to develop coatings that can increase the wear resistance of WE43 Mg alloys, which have a high potential for use due to their specific gravity, by using a method that can be easily applied in the industry. For this purpose, using the cold spray coating method, magnesium alloys, whose surfaces are highly active, are provided to be coated without oxidation and wear resistance is improved. In the study carried out, WE43 Mg alloys, which roughen the surfaces by fine sandblasting process, were used with cold spray method, using powders containing Al/Zn/Al2O3 and Zn/Al2O3 and trade names DYMET K-20-11 and DYMET K-00-11, respectively, using N2 shielding gas at 500 degrees C. 6 g/min for powders delivered to supersonic speeds under the atmosphere. The powder was sprayed onto the substrates using the feed rate. Morphological analysis of the coated and uncoated samples with different contents were examined by SEM, XRD methods, the coating thicknesses were measured with SEM images taken from the section, and the percentages of the elements were determined by EDS analysis. In addition, ball-on disc wear tests were performed to examine the wear performance and volume losses were evaluated. As a result, the wear loss of WE43 alloys was reduced by approximately 40% compared to the uncoated condition, thanks to the cold spray coatings.
EFFECT OF FERROBORON ON CORROSION RESISTANCE OF Fe-Cr-C HARDFACING COATINGS
Çömez, N; Gül, C; Durmus, H; Zeybek, MS
The hardfacing coatings provide a thick protective layer against corrosion owing to their hard carbide and/or boride compounds. This study aims to reveal the effect of boron content on corrosion resistance of iron-based hardfacing coatings. Hardfacing was applied by arc welding method using massive filler wire, ferrochromium (FeCr) and ferroboron (FeB) powders. The Vickers hardness (HV20) tended to increase with increasing amount of boron in the coating material. The corrosion rate of the coatings was measured according to the Tafel extrapolation method. The corrosion resistance decreased with increasing boron content. Minimum corrosion rate was observed in the boron-free coating.
From Metal Chips to Composite: Effect of Age-Hardening on Mechanical and Wear Properties of Al2O3 Reinforced AA7075 Composites
Durmus, H; Gül, C; Çömez, N; Uzun, R
Aluminum metal matrix composites were used in various fields such as aircraft, underwater, automobile, aerospace. Several fabrication techniques were used for the production of these composites. Among the various methods, the powder metallurgy route provides dimensional accuracy and high production rates. In this paper, metal matrix composites that include 7075 aluminum alloy chips and Al2O3 particles were produced by using a hot pressing. The effect of reinforcement amount and T6 heat treatment on the mechanical and wear properties of the composites were investigated. Al2O3 particles were added by weight of 5, 10 and 15 % and the composites were produced by hot pressing. T6 heat treatment consisted of a solution treatment at 480 degrees C for 2 h and artificially aging process at 120 degrees C for 24 h. Wear resistance of the composites was determined by a ball-ondisc dry sliding wear test. Brinell Hardness of the composites tended to increase with the increasing Al2O3 reinforcement up to 10 wt.% and with T6 treating. Particle reinforcement improved the wear resistance up to 10 wt.% Al2O3. In addition, volumetric material loss tended to decrease after the aging process.
Surface characterization of EPD coating on AZ91 Mg alloy produced by powder metallurgy
Aydin, I; Bahçepinar, AI; Gül, C
Intense implants which are used widely in biomedical applications such as Ti and its alloys and 316 L stainless steel can harm the surrounding tissues, hence may also cause infection. In order to eliminate this risk, it is necessary to produce new generation implant materials that are lighter than their existing biomaterials for use in biomedical applications and whose mechanical properties and structure are close to bone. In this study AZ91 Mg alloy implant material is created by using powder metallurgy method. In addition, in order to improve the bio-compatibility and bio-activity, the generated implant material was also coated with hydroxyapatite (HA) which is known as a ceramic based biomaterial. In this study, AZ91 Mg alloy is created by using powder metallurgy method. HA coating was applied to the alloy surface using the electrophoretic deposition method. The surface properties and corrosion resistance of the coatings made were examined. The applied voltage values in the coating process were determined as 100, 150, 200 and 250 V, the time parameter was stabilized as 2 minutes. HA, ethanol, polyvinyl alcohol (PVA), N, N-Dimethylformamide chemicals were used to prepare the coating solution. At the end of the study, microstructures of the coatings were examined by using scanning electron microscopy (SEM) and elemental analyzes (EDS) of the coating surfaces were performed. The X-ray diffraction method (XRD) was used to determine the phases of the coatings and its concentration. Coating thickness and surface roughness values were also determined. Corrosion behavior of coated samples was determined by potentiodynamic electrochemical potential corrosion test in artificial body fluid.
Reliability Analysis of Brinell Hardness Results for Aged Alumix321/SiC Composites
Gül, C; Çömez, N; Çivi, C; Durmus, H
Aluminum/SiC composites are widely employed in the automotive industry. Aluminum composites can be produced by hot pressing which forms a final product with a low porosity level and a denser structure. Homogeneous distribution of reinforcement particles, the level of porosity, and heat treatment not only affect the mechanical properties of the composites but also the reliability of their mechanical test results. In this study, Brinell hardness test reliability analyses of the hot-pressed Alumix321/SiC composites were carried out. The effects of increasing SiC amount and aging treatment on the reliability of hardness test results were discussed. Reliability analysis revealed that the aging treatment and increasing amount of SiC reinforcement decreased the reliability of the hardness test results. The reason for this was researched and resulting cases were discussed.
An investigation into the wear behavior of aged Alumix321/SiC composites fabricated by hot pressing
Durmus, H; Gül, C; Çömez, N; Yurddaskal, M
Aerospace or automobile industries need materials that have a combination of several features such as lightness, high strength, corrosion and wear resistance. With ceramic particulates reinforcement, the properties of aluminum alloys can be greatly improved. The aim of this study is to investigate the effect of precipitation age hardening and the mass percentage of SiC particles on hardness and wear resistance of the 6061 aluminum matrix composites produced by hot pressing. Composites were solution treated at 530 degrees C for 1.5 h and then artificially aged at 160 degrees C for 18 h. The ball-on-disc wear test was carried out under 2N load using an alumina ball as the counterpart. The density of the composites was calculated according to Archimedes principle. Porosity tended to increase with increasing SiC reinforcement. Hardness and wear resistance of composites were improved by SiC particles and aging. Maximum hardness and minimum wear loss was obtained heat treated sample that contains 20 wt.% SiC reinforcement.
Al/Zn/Al2O3 and Zn/Al2O3 Coatings by Cold Spray Coating Method of WE43 Magnesium Alloy and Investigation of Its Wear Behaviors
Gül, C; Albayrak, S; Çömez, N; Durmus, H
Mg alloys are preferred in automotive, aircraft, aerospace and communication industries due to their low specific gravity and high strength. WE series is a series of Mg alloys containing Mg, Y, Nd, rare earth elements, and although the creep strength is good for this alloy series, the wear resistance is open to improvement. The aim of this study is to develop coatings that can increase the wear resistance of WE43 Mg alloys, which have a high potential for use due to their specific gravity, by using a method that can be easily applied in the industry. For this purpose, using the cold spray coating method, magnesium alloys, whose surfaces are highly active, are provided to be coated without oxidation and wear resistance is improved. In the study carried out, WE43 Mg alloys, which roughen the surfaces by fine sandblasting process, were used with cold spray method, using powders containing Al/Zn/Al2O3 and Zn/Al2O3 and trade names DYMET K-20-11 and DYMET K-00-11, respectively, using N2 shielding gas at 500 degrees C. 6 g/min for powders delivered to supersonic speeds under the atmosphere. The powder was sprayed onto the substrates using the feed rate. Morphological analysis of the coated and uncoated samples with different contents were examined by SEM, XRD methods, the coating thicknesses were measured with SEM images taken from the section, and the percentages of the elements were determined by EDS analysis. In addition, ball-on disc wear tests were performed to examine the wear performance and volume losses were evaluated. As a result, the wear loss of WE43 alloys was reduced by approximately 40% compared to the uncoated condition, thanks to the cold spray coatings.

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