Sukuroglu, Suleyman; Totik, Yasar; Sukuroglu, Ebru Emine; Avci, Selcuk

LA91 magnesium alloy is a super lightweight magnesium -lithium alloy proposed for next generation materials. In addition to the advantages of these alloys such as low density, high strength-to -weight ratio, specific stiffness and brittleness, these alloys also have disadvantages such as low corrosion resistance and the oxide -carbonate film formed on the surfaces of the alloys cannot provide sufficient corrosion protection even in non-corrosive environments. In this study, micro arc oxidation, one of the coating methods, was applied to LA91 alloy. The surface morphologies of the coatings were characterized and it was aimed to increase the corrosion resistance of LA91 alloy. For this purpose, potentiodynamic polarization tests were carried out in 3.5% NaCl solution at room temperature to draw attention to the protection of the coating. As a result of the tests, it was determined that the oxide coatings raised on the surface

Sukuroglu, Suleyman; Sukuroglu, Ebru Emine; Totik, Yasar; Gulten, Gokhan; Efeoglu, Ihsan; Avci, Selcuk

Magnesium–lithium alloy is used in different areas of industry and is known as a super light metallic engineering material. However, the use of these alloys is limited due to their surface properties under extreme loads and aggressive environments. Surface treatments can be applied to these alloys to increase their usage areas and improve their weak surface properties. In this study, the micro-arc oxidation method was applied to improve the surface properties of LA91 alloy. The corrosion and adhesion behaviour of the coated samples were investigated. The lowest corrosion current density in the coatings was obtained under Experiment 3. Experiment 3 has the highest Lc2 value due to the coating thickness and the denser and smaller diameter pores of the functional intermediate layer.

Kucukosman, Rıdvan; Sukuroglu, Ebru Emine; Totik, Yasar; Sukuroglu, Suleyman

Graphene oxide (GO) integrated composite coatings were deposited on AZ91 magnesium alloys by the PEO (Plasma Electrolytic Oxidation) and the treatment which has a post-PEO hydrothermal process. For the first group samples, PEO was performed in the silicate/phosphate-based electrolyte including 5–10 µm in size the GO particles synthesized using the Tour Method. For the second group samples, after PEO treatment, the post-PEO hydrothermal process was carried out in the oven in the GO-distilled water mixture containing GO produced with the same protocol. The effects of GO on wear behavior, structural and morphological features of composite coatings were examined with a pin-on-disc tribometer, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy, respectively. The results showed that the addition of GO improved significantly the adhesion to the substrate material of composite coatings, increased the coating thickness and hardness. Post-PEO hydrothermal process resulted in the formation of partial a thin solid lubricant GO film on the surface of composite coatings and thus exhibited the best wear and friction resistance.

Matin, Reza; Totik, Yasar; Sukuroglu, Ebru Emine; Efeoglu, Ihsan; Santos, Telmo G.

It is said that plasma electrolytic oxidation (PEO) is considered as an effective technique to boost the surface properties of light materials by means of forming ceramic films on their surfaces. In this study, three different voltage values were applied to the PEO process to AA2024 so that Al2O3 ceramic coatings were directly supplied for AA 2024 substrates by PEO and it is focused on the adhesion of interface between coating and substrate. All of the cases such as microstructure, phase composition, thickness, roughness and hardness of Al2O3 ceramic coatings were assayed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Atomic-force microscopy (AFM), Eddy Current Non-destructive testing and microhardness test, respectively. The results showed that roughness, hardness and thickness of the coatings were increased as we increased the voltage. Therefore, it could be claimed that the voltage parameters have an important role in the unified coating on the metal surface as it is directly connected with the morphologies of the PEO coating.

Sukuroglu, Ebru Emine; Farzi, Hamed; Sukuroglu, Suleyman; Totik, Yasar; Arslan, Ersin; Efeoglu, Ihsan

Despite the fact that Titanium and its alloys are materials which have excellent corrosion-resistant properties, they have poor wear and friction performance under tribological conditions. The aim of this study is to find suitable parameters for the surface treatment of Cp-Ti substrates which are used under saline environment. In this study, TiO2 coatings were grown on Cp-Ti substrates at different frequencies which are parameters of the coating process. Due to its low cost and ability to achieve high thicknesses, The Plasma Electrolytic Oxidation (PEO) method was applied to grow TiO2 coatings. The microstructures, morphology, and crystallographic structure were analyzed using SEM and XRD. Tribocorrosion properties of the coatings were investigated using a combination of the pin-on-disk wear test and potentiodynamic polarization test units. The frequency is known to have a strong impact on the PEO process. The impacts of frequency changes on the PEO coating performance were examined under a constant voltage. As result, the increase of the frequency caused smaller pores and cracks in the surface morphology of the coating and at the same time this yielded an increment on the tribocorrosion behavior of the coating.

Sukuroglu, Ebru Emine; Sukuroglu, Suleyman; Akar, Kubra; Totik, Yasar; Efeoglu, Ihsan; Arslan, Ersin

NiTi alloys exhibit good properties, such as shape memory behavior, high corrosion resistant, having the closest elasticity modulus of a human bone and superior biocompatibility properties. However, the surface problems that arise during the use of this alloy limit the usage in the industry and health sector. In recent years, micro-arc oxidation method is used to improve the surface properties and increase the usage of these alloys. In this study, the TiO2 coatings were deposited on the NiTi substrates. The surface topography, morphology, crystallographic structure, and thickness of the coatings were determined using scanning electron microscopy and X-ray diffraction. The corrosion properties were investigated using potentiostat test unit in two different media such as NaCl solution and simulated body fluid. The results show that the coated samples have higher corrosion resistance than uncoated samples in the two different media.

Sukuroglu, Ebru Emine; Totik, Yasar; Arslan, Ersin; Efeoglu, Ihsan

In recent years, various technologies have been increasingly investigated for the surface modification of Ti and Ti alloys. Microarc oxidation (MAO) is one of the effective techniques to improve surface properties. However, it has some disadvantages for sliding wear applications and/or aggressive environments. In this study, the combined MAO and closed field unbalanced magnetron sputtering process was used to deposit duplex MAO/diamond-like carbon (DLC) coatings on Ti6Al4V alloy. Analysis of the microstructures, morphology, and crystallographic structure were performed by using a SEM, Raman, and XRD. The wear, corrosion, and tribo-corrosion properties of the coatings were investigated using the pin-on-disk wear test, potentiodynamic polarization test, and combining tribo-corrosion test unit, respectively. The results of this study have shown that duplex MAO/DLC coatings exhibit better wear, corrosion, and tribo-corrosion properties than the DLC or MAO monolayer on Ti6Al4V alloy substrate. MAO/DLC coatings exhibited dense structure, lower coefficient of friction and corrosion current density, and higher tribo-corrosion resistance. The results have also shown that MAO/DLC duplex coatings on Ti6Al4V substrates increased the tribo-corrosion resistance by acting as a barrier layer.