Browsing by Author "Yilmazer, H."

Now showing 1 - 4 of 4

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.
Electrochemical Behaviors of Biomedical Nano-Grained Β-Type Titanium Alloys
(Trans Tech Publications Ltd, 2017) Yilmazer, H.; Dikici, B.; Niinomi, M.; Nakai, M.; Lui, H.; Todaka, Y.; Ozcivan, A.N.
The microstructural evolution and its effect on biocompatibility of TNTZ through HPT processing were investigated systematically in this study. TNTZAHPT shows an enhanced mechanical biocompatibility, which is characterized by a higher tensile strength (1375 MPa) and hardness (450 HV) than those of TNTZST, TNTZAT, and Ti64 ELI while maintaining a relatively low Young’s modulus. In this study, such microstructural refinement of TNTZ and its effect on electrochemical biocompatibility through HPT processing are investigated systematically in this study. The microstructure of TNTZAT consists of randomly distributed needle-like α precipitates in the equiaxed β grains with a diameter of approximately 40 m. The microstructure of TNTZAHPT consists of nano-grained (NG) elongated β grains that have subgrains of non-uniform morphologies resulting from distortion by severe torsional deformation. Furthermore, the β grains and subgrains are surrounded by non-equilibrium grain boundaries. The needle-like α precipitates are completely refined to a nano-grained. TNTZAHPT exhibits an enhanced combination of excellent corrosion performance and improved cellular response compared to TNTZST, TNTZAT, and Ti64 ELI. © 2017 Trans Tech Publications, Switzerland.
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.
Synthesis and Characterization of Hydroxyapatite/Tio2 Coatings on the Β-Type Titanium Alloys With Different Sintering Parameters Using Sol-Gel Method
(Maik Nauka/interperiodica/springer, 2018) Dikici, B.; Niinomi, M.; Topuz, M.; Say, Y.; Aksakal, B.; Yilmazer, H.; Nakai, M.
In this study, hydroxyapatite (HA) based composite films were successfully syntheses on the beta-type Ti29Nb13Ta4.6Zr (TNTZ). The solutionized TNTZ substrates coated with HA and HA/Titania (TiO2) bioactive composite coatings by sol-gel method under various sintering parameters related to sintering temperatures and heating ramp rates. Microstructural observations of the coatings revealed that apatite was formed on the substrates. The hardness values of the coatings increase with increasing both the sintering temperature and the TiO2 concentration in the coatings layer. However, it was found that the heating ramp rate of the sintering was not affecting the hardness values so much. Also, the hardness values of the HA/TiO2 composite coatings at all sintering temperatures were higher than only HA coated TNTZ samples due to the existence TiO2 phases in the HA matrix. Results indicating that the doping of HA with TiO2, improve the physical consistency between the coating layer and the substrates and provide a better inter-particle bonding due to the existence TiO2 phases in the HA.