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1

Characterization of thermally oxidized titanium based coating

Cetiner D., Paksoy A. H., Tazegul O., Atar E., Cimenoglu H.

Journal of Achievements in Materials and Manufacturing Engineering

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2016

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Vol. 75, nr 2

49--54

EN

Purpose: Aim of the study is to improve the bioactivity of CoCr alloy upon covering the surface with titanium based coating. Design/methodology/approach: CoCr alloy was coated by cold spraying of powder mixture having a composition of 92 wt.%Ti + 8 wt.%Al. Coated samples were thermally oxidized at 600°C for 60 hours. Characterization of the coating was made by X-Ray diffraction analyses, microstructural surveys, cross-section and surface SEM elemental mapping analyses, roughness and hardness measurements. Findings: Results showed that sequential application of cold spray and thermal oxidation processes provided the multi-layered coating consisting of an inner titanium based layer and an outer oxide layer consisted of TiO2 and Al2O3. Thermal oxidation also caused the remarkable increasing in the surface hardness as compared to the as-cold sprayed state. Practical implications: Modifying the surface of CoCr metallic implants for long term success. Originality/value: Producing a multilayer coating on the surface of the CoCr alloy for biomedical application by sequential application of cold spray and thermal oxidation processes is the orginality of the study.

2

Characteristic of MAO coatings formed on CuAl2 in-situ reinforced Aluminum Matrix Composites

Mafouz D. I., Paksoy A. H., Muhaffel F., Tazegul T., Cimenoglu H.

Archives of Materials Science and Engineering

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2016

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Vol. 79, nr 2

60--63

EN

Purpose: The aim of this study was to examine the structural and mechanical properties of coatings formed on CuAl2 in-situ reinforced aluminium matrix composites (AMCs) by micro arc oxidation (MAO) process. AMC, which were fabricated by powder metallurgy method upon addition of copper powder into aluminium powder at different percentages (0%, 15 wt.% and 30 wt.%), were exposed to MAO after sintering at 550°C for 6 h. During sintering process CuAl2 type intermetallic was precipitated in the microstructure of copper containing compacts. MAO caused covering of the surfaces of AMCs with an oxide layer mostly consisting of mullite and alumina. Mechanical performance of the coatings were determined by hardness measurements and wear tests. In summary, the oxide layers formed on the AMCs exhibit a reduction in hardness and tribological performance with increasing copper content of the AMC.

3

Copper matrix composite coatings produced by cold spraying process for electrical applications

Tazegul O., Dylmishi V., Cimenoglu H.

Archives of Civil and Mechanical Engineering

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2016

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Vol. 16, no. 3

344--350

EN

Composite coatings were deposited on commercially pure copper substrates by cold spraying of feedstock consisted of copper and Al2Cu powders. The amount of the Al2Cu powder incorporated in the feedstock varied in between 0 and 15 vol.%. Characterisations of the coatings were done by microstructural examinations, hardness and electrical conductivity measurements and wear tests. Composite coatings deposited from the feedstock containing 5 and 10 vol.% Al2Cu powder exhibited better electrical conductivity and superior wear resistance than the monolithic (Al2Cu free) copper coating. Presence of 15 vol.% Al2Cu in the feedstock diminished both the wear resistance and the electrical conductivity of the coating.

4

The effect of nickel on sliding wear behaviour of cobalt-based hardfacing alloy at elevated temperature

Motallebzadeh A., Atar E., Cimenoglu H.

Archives of Materials Science and Engineering

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2014

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Vol. 69, nr 2

81--87

EN

Purpose: To investigate the effect of addition of nickel on the microstructure, hardness and tribological properties of cobalt-based hardfacing alloy (Stellite 12) deposited by plasma transferred arc (PTA) welding technique. Design/methodology/approach: Microstructural characterization was carried out on deposited layers by utilising X-ray diffractometer and energy dispersive X-ray (EDX) equipped scanning electron microscope (SEM). Mechanical properties of the coatings were determined by hardness measurements and sliding wear tests. Hardness of the deposited layers was evaluated in HV scale. Wear tests were conducted under normal load of 3 N at room temperature (RT), 300 and 500ºC. Findings: Microstructural studies revealed that addition of nickel into Stellite 12 alloy dominated FCC crystal structure in the cobalt rich solid solution matrix rather than HCP crystal structure. Furthermore, nickel addition reduced the hardness and wear resistance of the deposited layer at room temperature. Nickel containing Stellite12 deposited layers demonstrated better wear resistance as compared to a Stellite12 deposited layer at high temperatures (300 and 500°C) owing to the formation of stable oxide layer on the worn surface. Practical implications: Determining the sliding wear performance of Stellite 12 alloy deposited layer which nickel is added to enhance the corrosion resistance in harsh environments. Originality/value: The investigation of high temperature wear performance of Stellite 12 alloy deposited layer upon addition of nickel.

5

Preparation and characterization of hydrothermally treated hydroxyapatite containing titania layer on commercially pure titanium

Teker D., Muhaffel F., Cimenoglu H.

Archives of Materials Science and Engineering

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2014

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Vol. 68, nr 1

5--9

EN

Purpose: To investigate the effect of hydrothermal treatment (HT) on bioactivity of micro arc oxidized (MAO) and MAO/) commercially pure titanium (Cp-Ti). Design/methodology/approach: Cp-Ti (Grade IV) samples were oxidized in order to generate titania layer via micro arc oxidation (MAO) process. The samples were treated at 400 V for 5 minutes in a calcium acetate hydrate and disodium hydrogen phosphate anhydrous containing electrolyte. Subsequently, hydrothermal treatment (HT) was applied on oxidized surface in an autoclave with a water solution whose pH adjusted to 11.0-11.5 by adding NaOH, at 200 and 230°C for 2.5, 5 and 10 h and cooled in the autoclave to achieve improved bioactivity behaviour. The bioactivity tests were employed by soaking the samples in a 1.5X simulated body fluid (SBF) to characterize biological response of treated surfaces. The mean elemental composition, surface and cross-sectional morphology, phase composition and surface roughness were examined by energy dispersive spectrometer (EDS) equipped scanning electron microscopy (SEM), X-ray diffractometer (XRD) and profilometer, respectively. Findings: It is found that after MAO+HT process, the surface roughness of the samples was reduced due to the homogeneous distribution of HA agglomerates. The improved surface properties of CP-Ti modified with micro arc oxidation and hydrothermal treatment showed that it can be a good potential candidate for biomedical applications instead of bare CP-Ti. Originality/value: Different HT conditions parameters and the hydroxyapatite crystallization mechanism on oxidized surfaces of the Cp-Ti samples was examined.

6

An investigation on the mechanical properties of the hard chromium layer deposited by brush plating process on AISI H13 steel

Aydin Z., Aldic G., Cimenoglu H.

Archives of Materials Science and Engineering

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2014

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Vol. 65, nr 2

87--92

EN

Purpose: This study aims to investigate the potentiality of brush chromium plating process to replace conventional hard chromium plating. Design/methodology/approach: In this study brush chromium plating was applied over a H13 quality tool steel. Electron microscopy examinations and X-ray diffraction analysis were conducted in order to reveal the structural features of the coatings. Mechanical properties of the coatings were determined by hardness measurements and wear tests. Wear tests were conducted at room temperature and 500°C. Findings: Brush chromium plating, which is an environmental friendly alternative for conventional chromium plating, has potentiality to enhance wear resistance of steels. Research limitations/implications: Brush chromium plating process has good potential to replace hexavalent chromium. Further studies should focus on effect of electro-chemical parameters on structural properties of trivalent based hard chromium deposit by brush plating process. Originality/value: There have been significant researches on replacement of hexavalent based hard chromium plating in literature. Replacement by brush plating process with trivalent chromium containing electrolyte has been scarcely investigated especially for utilization in wear related applications at elevated temperatures.