Browsing by Author "Ozdemir, I."

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The Effect of Post-Heat Treatment on Microstructure of 316l Cold-Sprayed Coatings and Their Corrosion Performance
(Springer, 2016) Dikici, B.; Yilmazer, H.; Ozdemir, I.; Isik, M.
The combined effects of process gases and post-heat treatment temperature on the microstructure of 316L cold-sprayed coatings on Al5052 substrates have been investigated in this study. The stainless steel coatings were subjected to heat treatment at four different temperatures (250, 500, 750, and 1000 degrees C) to study the effect of heat treatment. In addition, the corrosion performances of the coatings at different process temperatures have been compared using the potentiodynamic scanning technique. Microstructural characterization of the coatings was carried out using scanning and transmission electron microscopy and x-ray diffraction. The results of present study showed that cold-sprayed stainless steel coatings processed with helium exhibited higher corrosion resistance than those of coatings sprayed with nitrogen process gas. This could partially be attributed to the reduction in porosity level (4.9%) and improvement of particle-particle bonding. In addition, evaluation of the mechanical and microstructural properties of the coatings demonstrated that subsequent heat treatment has major influence on the deposited layers sprayed with He process gas.
Feb and Feb/H-bn Based Anti-Corrosive Composite Coatings for Aluminium Alloys
(Emerald Group Publishing Limited, 2012) Dikici, B.; Ozdemir, I.
Purpose - The purpose of this paper is to investigate the corrosion behaviour of ferroboron (FeB) and FeB/h-BN (hexagonal boron nitride) coatings deposited onto A383 substrates by atmospheric plasma spraying. Design/methodology/approach - Potentiodynamic scanning (PDS) and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion susceptibilities of the composite coatings. Microstructural characterizations were carried out by using scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). Findings - It was observed that the coatings resisted localized corrosion in NaCl solutions and protective oxide films on the coatings repaired themselves over the corrosion potential. Hexagonal-BN is not only a limiting factor in the corrosion of the FeB based coatings. The corrosion morphologies of the coatings are strictly dependent on pores and micro-cracks in the coating. Practical implications - The iron-based borides act as solid lubricants and have a positive influence on tribological properties such as hardness, friction and corrosion of the coating. Originality/value - Knowledge of the effects of FeB on the corrosion behaviour of thermal spray coatings is still incomplete and this is the most important obstacle to the widespread use of the coatings in engineering applications. The paper reports electrochemical test results of the coatings and discusses the morphologic effects of h-BN on the corrosion behaviour.
Preparation and Characterization of Chitosan/Hydroxyapatite Sol-Gel Coating on Ti-6al
(Certex, INCDTP-ICPI, 2016) Gungor Koc, S.; Dikici, B.; Topuz, M.; Yilmazer, H.; Ozdemir, I.; Niinomi, M.; Nakai, M.
A biocomposite coating containing chitosan and hydroxyapatite was developed on Ti-6Al-4V substrate by a sol-gel method in order to obtain a biocompatible and antimicrobial implant surface which can be used to create a smooth transmucosal region for a faster and better wound healing and an increased bioactivity. The coatings characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and differential thermal analysis (DTG). Scratch test was carried out to evaluate the adhesion between the coated film and the substrates. The critical load at which the coating film was peeled off from the substrate is determined by using the spherical diamond stylus. The results revealed that the coating roughness is approximately 0.23. The critical load for debonding the coating film from the substrate was determined between 6 to 11N. Only a little wear debris was come out from the coating film in the initial stage of a small-applied load. With increasing the load, the coating film became crushed and finally worn away. © 2016 Certex, INCDTP-ICPI.