Browsing by Author "Comakli, Onur"

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Bn-TiO2 Multilayer Coating on Az91 for Enhanced Corrosion Performance in Marine Environments
(Univ Fed Rio de Janeiro, Lab Hidrogenio, 2024) Meletlioglu, Emrah; Comakli, Onur
Magnesium alloys have recently been used in marine applications due to an attractive combination of low density and high strength/weight/ratio. However, the corrosion resistance of magnesium alloys should be improved for practical applications. In this study, BN-TiO2 multilayer films were deposited with different numbers of bilayers (2 and 4) on AZ91 magnesium alloys to enhance the corrosion resistance of magnesium alloys in marine environments. The microstructure and wettability properties of uncoated and multilayer film-coated alloys were comparatively investigated via XRD, SEM, AFM, and contact angle measurement systems. The corrosion performance of uncoated and coated samples has also been evaluated using electrochemical polarization and impedance measurements in artificial seawater. The corrosion performance values of multilayer film-coated alloys were better than the uncoated alloy values. Corrosion resistance and hydrophobicity of coated samples also increased with the number of bilayers owing to the smaller grain size, increased layered interfaces, and high structural density.
Effect of Bilayer Numbers on Structural, Mechanical, Tribological and Corrosion Properties of TiO2-SiO2 Multilayer Film-Coated Β-Type Ti45Nb Alloys
(Elsevier Sci Ltd, 2023) Comakli, Onur; Yazici, Mustafa; Demir, Merve; Yetim, Ali Fatih; Celik, Ayhan
Protective films with excellent tribological performance and good corrosion resistance are needed in general because titanium implants are used in aggressive environments and always suffer from severe wear and corrosion. In this study, TiO2-SiO2 multilayer films were deposited with different numbers of bilayers (2, 4, and 8) on beta-type Ti45Nb alloy substrates by physical vapour deposition. The influence of number of bilayers on microstructure, wettability, mechanical features, tribological performance and electrochemical behaviour of TiO2-SiO2 multilayer films were comparatively observed via XRD, XPS, SEM, AFM, nanoindentation tester, contact angle measurement system, reciprocating tribo-tester, and electrochemical corrosion media. The surface hardness, wear and corrosion resistance values of multilayer film-coated substrates were higher than the untreated substrate values. These properties and adhesion resistance and hydrophobicity of coated samples also increased with increase in number of bilayers due to the smaller grain size, increased layered interfaces and high structural density.
Effect of Scan Speed on Corrosion and Tribocorrosion Properties of Cobalt-Chromium Alloy in Situ Produced by Selective Laser Melting
(Emerald Group Publishing Ltd, 2024) Alaloosi, Raghad Ahmed; Comakli, Onur; Yazici, Mustafa; Taha, Ziad A.
Purpose - This paper aims to investigate the influence of scan speed on the corrosion and tribocorrosion features of the CoCrMoW samples fabricated via the selective laser melting (SLM) process.Design/methodology/approach - CoCrMoW samples were produced by SLM at different scan speeds. Produced samples were made via structural surveys (X-ray diffraction examinations and scanning electron microscopic analyses), hardness measurements and electrochemical and tribocorrosion experiments.Findings - Outcomes displayed that the corrosion and tribocorrosion properties of CoCrMoW alloy were significantly influenced by scanning speeds. Also, these properties of the alloy increased with increasing scanning speeds. CoCrMoW samples produced at a laser scan speed of 1,000 mm/s showed the best resistance to corrosion and tribocorrosion. This could be related to the high hardness and low grain structure of the fabricated samples.Originality/value - This paper may be a practical reference and offers insight into the effect of scanning speeds on the increase of hardness, tribological and corrosion performance of CoCrMoW alloys. This study can help in the further advancement of cobalt-chromium alloy in situ produced by SLM for both electrochemical and tribocorrosion behavior for biomedical applications.
The Effects of Aging Time on the Structural and Electrochemical Properties of Composite Coatings on Cp-Ti Substrate
(Springer Singapore Pte Ltd, 2017) Comakli, Onur; Yazici, Mustafa; Yetim, Tuba; Yetim, Ali Fatih; Celik, Ayhan
TiO2-SiO2 composite films were produced on commercially pure titanium (CP-Ti) substrate by a sol gel method to investigate the behavior of sol aging time and its potential effects on the structural and electrochemical properties of composite coatings. Anatase-TiO2 and quartz-SiO2 peaks were observed on all composite coated samples according to XRD results. It was observed that the average grain size increased with sol aging time. Also, the average smallest grain size was seen at composite coatings prepared from unaged sol according to the width of the peaks. Electrochemical behavior of coated samples was mainly investigated by potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) in Simulated Body Fluid (SBF) solution. In corrosion tests, the composite coatings showed better anti-corrosion behavior than that of uncoated samples. In addition, the corrosion properties of the composite films were considerably affected by sol aging time. Corrosion resistance of coatings decreased with increasing aging time and the best result was obtained from composite coatings prepared from unaged sol.
The Electrochemical and Tribocorrosion Behavior of Hybrid Ceramic Film-Coated Ti Alloys
(Elsevier Sci Ltd, 2024) Comakli, Onur; Yazici, Mustafa; Atmaca, Abdulhamit; Yetim, Tuba
In this study, anodic TiO2 ceramic coating was formed on titanium alloys produced by SLM by using the anodization method. After then, hybrid ceramic coatings are produced by combining a formation of ZrO2 nanostructures in the TiO2 coating with the SILAR technique. The microstructure, wettability, electrochemical properties, and tribocorrosion behavior of anodic TiO2 and hybrid ceramic coatings were also investigated. According to XRD results, two TiO2 peaks are observed in anodic TiO2 films. After the SILAR process, the tetragonal-ZrO2, and monoclinic-ZrO2 with TiO2 peaks were obtained in the hybrid ceramic coatings. Especially, while the intensity of the TiO2 peaks decreased, the intensity of the ZrO2 peaks increased with the increase in cycle time. The surface wettability experiments indicate that the HB-80 specimen exhibits superhydrophobic behavior, and it also has the highest contact angle value among all specimens. Corrosion tests in SBF solution confirmed that hybrid ceramic films importantly increased the anticorrosion performance of anodic TiO2 film, depending on the cycle times owing to filling the pores, and the best outcomes for corrosion resistance were obtained from the HB-80 specimen owing to its superhydrophobic properties. Moreover, the results of tribocorrosion tests revealed that all hybrid ceramic films displayed higher tribocorrosion resistance than anodic TiO2 ceramic film and uncoated Ti6Al4V substrate, and the best performance was seen from the HB-80 specimen due to its decreased porosity and the direct contact area between pin and surface.
Electrochemical Behavior of Tin Ceramic Films Coated on Ti Alloys Produced by SLM: The Effect of Different Body Fluid Environments
(Springer, 2025) Yazici, Mustafa; Comakli, Onur; Yetim, Tuba; Yetim, A. Fatih
In this study, TiN ceramic coating was deposited on Ti6Al4V alloys produced in SLM (Selective Laser Melting) using the PVD (Cathodic Arc Physical Vapor Deposition) method. After the deposition process, the all samples were analyzed for determining the film structure and their electrochemical behavior. All corrosion measurements were conducted in three different electrolyte mediums as simulated body fluid (SBF), simulated saliva fluid (SSF), and Dulbecco's Modified Eagle Medium (DMEM). When the OCP values were evaluated, it was observed that higher potentials were required for the initiation of corrosion in TiN coated samples than in untreated samples. When the behaviors of the coated samples in different environments were compared, it was obtained that the corrosion potential was fixed at the lowest values in the DMEM medium and at the highest values in the saliva medium. The Rp value of the TiN coated sample in the SSF medium was found as 236.85 k Omega cm2 from the potentiodynamic measurements. It was measured that Rp values of about 101.85 and 77.13 k Omega cm2 for TiN coated samples, in SBF and DMEM medium, respectively. EIS measurements were carried out to observe the electrochemical behavior of untreated and TiN coated samples. The best corrosion resistance behavior from EIS measurements was obtained in SSF medium.
Enhanced Tribocorrosion and Corrosion Resistance of R4 Grade Mooring Chain Steel Through Hybrid Ceramic Coatings
(Elsevier Sci Ltd, 2025) Comakli, Onur; Meletlioglu, Emrah
This study investigates the microstructure, corrosion resistance, and tribocorrosion properties of a hybrid ceramic layer applied to R4-grade mooring chain steel. The coatings were produced using a two-step process: boriding followed by applying a titanium carbon-nitride (TiCN) layer via the Physical Vapor Deposition (PVD) process. X-ray diffraction (XRD) tests verified the creation of FeB, Fe2B, and TiCN phases. The borided layer provided a gradient-hardened structure, improving load-bearing capacity, while the TiCN film enhanced surface hardness. The electrochemical tests demonstrated that the hybrid ceramic coating considerably enhanced corrosion resistance compared to untreated and borided samples. Tribocorrosion tests revealed that the hybrid ceramic layer exhibited superior wear resistance, with a lower coefficient of friction and reduced wear rates. These findings indicate that the hybrid ceramic coating system can significantly enhance electrochemical and tribocorrosion resistance in seawater, extending the service life of R4 steel.
Improved Structural, Mechanical, Corrosion and Tribocorrosion Properties of Ti45nb Alloys by Tin, Tialn Monolayers, and Tialn/Tin Multilayer Ceramic Films
(Elsevier Sci Ltd, 2021) Comakli, Onur
In this study, TiN, TiAlN monolayers, and TiAlN/TiN multilayer ceramic films on the surface of Ti45Nb substrates were formed via the cathodic arc physical vapour deposition process. The samples were characterized by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy, nano-indentation testing and surface tension testing. The corrosion performance of the samples was evaluated via potentiodynamic polarization and electrochemical impedance spectroscopy measurements and their tribocorrosion behaviour was evaluated by a ball on flat reciprocating tribotester in which the tribological contact was immersed in the electrolyte. The obtained structural and mechanical results indicated that multilayer films have finer grain sizes, and more stable and harder film structures compared with the monolayer coatings. Moreover, the surfaces of the samples exhibited different wetting characteristics. While uncoated and single layer (TiN, TiAlN) coatings showed hydrophilic behaviour, the multilayer coating exhibited hydrophobic behaviour. During the corrosion and tribocorrosion tests, all of the coatings showed a protective feature due to the ceramic structure of the coatings against corrosion and tribocorrosion. Among all of the ceramic coatings, the best results were obtained for the multilayer film.
Improvement of Two-Body Wear Behavior and Biocompatibility of Ti15Mo Alloys in Dental Applications by Tin, TiCN Coatings
(Springer, 2025) Comakli, Onur; Meletlioglu, Emrah; Sadeler, Furkan; Cakir, Mevra Aslan
This study investigates the tribological performance, antimicrobial properties, and cytotoxicity of Ti15Mo alloys coated with TiN and TiCN via physical vapor deposition (PVD). The alloys were subjected to a two-body wear test in distilled water, simulating 2 years of clinical use in a chewing simulator. The wear testing demonstrated a significant reduction in wear volume loss for both TiN and TiCN coatings compared to the uncoated Ti15Mo substrate. TiCN exhibited superior wear resistance, as evidenced by lower friction coefficients and minimal wear damage. X-ray diffraction and X-ray photoelectron spectroscopy validated the achieved coating of compact, homogeneous coatings. Scanning electron microscopy images revealed columnar microstructures with an approximate thickness of 2.5 mu m. Antibacterial assays indicated a notable reduction in bacterial adherence and growth on the coated surfaces, with TiCN displaying the most significant antibacterial performance against Staphylococcus aureus and Escherichia coli. Cytotoxicity was assessed through MTT assays, showing that TiN and TiCN coatings exhibited high biocompatibility, with cell viability above 70%. These findings demonstrate that TiN and TiCN coatings significantly enhance the wear resistance, antibacterial performance, and biocompatibility of Ti15Mo alloys, positioning them as viable candidates for advanced biomedical applications.
Influence of CrN, TiAlN Monolayers and TiAlN/CrN Multilayer Ceramic Films on Structural, Mechanical and Tribological Behavior of β-Type Ti45Nb Alloys
(Elsevier Science Ltd, 2020) Comakli, Onur
CrN, TiAlN single layers, and CrN/TiAlN multilayer ceramic films were deposited on Ti45Nb substrates by an industrial cathodic arc PVD process. The phase structures, the cross-sectional morphology, adhesion strength, surface hardness, and tribological behavior of the resulting uncoated and coated samples were evaluated in detail. The results showed that the preferred orientation was changed from (200) in CrN and TiAlN single layer films to (111) plane in the TiAlN/CrN multilayer films. The multilayered TiAlN/CrN films had smaller crystallite size than the single CrN and TiAlN films. The multilayer film coated samples exhibited the maximum surface hardness and the best adhesion strength among all samples. In addition, the results of wear tests present that all ceramic coatings showed better tribological properties than uncoated TiNb45 substrate materials and the best performance was observed from multilayer film-coated samples.
Influence of Scanning Velocity on a CoCrMoW Alloy Built Via Selective Laser Melting: Microstructure, Mechanical, and Tribological Properties
(Springer, 2023) Al-Aloosi, Raghad Ahmed; Comakli, Onur; Yazici, Mustafa; Taha, Ziad A.
In this study, CoCrMoW samples were produced by selective laser melting (SLM). The influence of scanning velocity on the microstructure, mechanical, and wear properties of the fabricated samples was investigated. Experimental outcomes indicated the samples produced with higher scan velocity showed higher microhardness as well as higher tensile strength values due to refined grains. Also, these values increased with increasing scan velocity. The influence of scan velocity on the wear performance of the CoCrMoW alloys was observed. Although the COF values of the samples increased with the increment in scanning velocity, their wear rate decreased. The excellent wear resistance of the samples fabricated with laser scanning velocity of 1000 mm/s could be related to their high microhardness. Furthermore, this work may help in the further advancement of CoCrMoW alloys.
Investigation of Mechanical, Tribological and Magnetic Properties After Plasma Nitriding of AISI 316L Stainless Steel Produced with Different Orientations Angles by Selective Laser Melting
(Elsevier Science Sa, 2023) Yazici, Mustafa; Comakli, Onur; Yetim, Tuba; Yetim, Ali Fatih; Celik, Ayhan
In this study, AISI 316L stainless steel samples were produced with different orientations (0 & DEG;, 45 & DEG;, and 90 & DEG;) using selective laser melting (SLM). In addition, plasma nitriding of the samples produced with SLM was performed at 400 & DEG;C for 4 h. The effect of different orientation on the structural, mechanical, tribological, and magnetic properties of 316L stainless steel was investigated. The same measurements also were made after the plasma nitriding process. The results showed that the phase composition and microstructure of the non-nitriding and nitridied samples were affected from the built orientation. Especially the XRD peaks shifted to the left with a decrease in the orientation angle. It was obtained that the highest modified layer thickness was measured from the samples produced with an angle of 0 & DEG;. It was observed that the surface hardness, residual stress, wear resistance and antimagnetization tendency values of nitridied samples were higher than the non-nitriding samples. Furthermore, these values tended to increase with the decrease in build orientation angles.
Tribological and Electrochemical Behavior of Ag2O/ZnO Nanocomposite Coating on Commercial Pure Titanium for Biomedical Applications
(Emerald Group Publishing Ltd, 2019) Comakli, Onur; Yatim, Fatih; Yazici, Mustafa; Yetim, Tuba; Celik, Ayhan
Purpose This paper aims to investigate the structural, tribological and electrochemical properties of Ag2O, ZnO, NiO coatings and Ag2O/ZnO/NiO nanocomposite films deposited on commercially pure titanium. Design/methodology/approach Ceramic thin films (Ag2O, ZnO, NiO coatings and Ag2O/ZnO/NiO nanocomposite film) were deposited on commercially pure titanium (CP-Ti) substrate. Surface characterization of the uncoated and coated samples was made by structural surveys (scanning electron microscopic examinations and X-ray diffraction analyses), hardness measurements, tribological and corrosion experiments. Findings Results were indicated that sol-gel coatings improved the wear and corrosion resistance of CP-Ti, and the best results were seen at the nanocomposite coating. It may be attributed to its small grain size, high surface hardness and high film thickness. Originality/value This study can be a practical reference and offers insight into the influence of nanocomposite ceramic films on the increase of hardness, tribological and corrosion performance. Also, the paper displayed a promising approach to produce Ag2O/ZnO/NiO nanocomposite coating on commercially pure titanium implants for biomedical applications.