An investigation of fracture and wear behavior of ha coatings deposited onto Ti6Al4V alloys in a new environment

The objective of this thesis is to investigate the fracture and wear behaviour of calcium phosphate based hydroxyapatide (HA) [HA:Ca10(PO4)6(OH)2] coatings that were deposited on to Ti6Al4V substrate in a new buffer environment. In this research, CaP coating processes were carried out by using citric acid-sodium citrate buffer system that would not show any toxic effect on human body and by preparing the solution of SBF (SBF-Synthetic/Simulated Body Fluids).In this research, 10 mm x 10 mm x 1.2 mm of square material as the substrate and ø19 x 25.4mm, ø28 x 25.4 mm of implants made of Ti6Al4V alloys in accordance with ASTM F 1044-99 and F 1658-95 standards were used. In this study, Ti6Al4V alloy implants were grounded before, cleaning with detergent and distilled water, and then he washed with acetone. At the same time, the materials cleaned in ultrasonic bath were kept in the oven in the solution of 5M NaOH + H2O2 for one day and left for drying at 600C for 24 hours. Then they were cooled after being kept at 6000C for one hour. Synthetic body solution (SBS) of 2 liter having pH~7,4 was prepared at 37 0C after these processes. Then the materials were coated by biomimetic method by shaking separately for 12, 18, 24, 48, 72 and 96 hours at 37 0C. Then the materials were washed up with distilled water and dried at 60 0C for 24 hours. Coatings at different intervals were carried out separately. Materials were tested mechanically and metalographicaly after coating processes.Ti6Al4V surface of the material, using citric acid-sodium citrate buffer solution in the SBFsolution, the different durations of HA coatings were subjected to wear test, the friction coefficients and wear behaviour were determined. In addition, coating, thickness, surface roughness, hardness, fracture toughness were determined and elastic modules were calculated. Stracth test device was used to measure the resistance against adherence of coating plates on to the surface. Besides, the micro structures of coatings were monitored with scanning electron microscopy (SEM), elemental analysis of coating surfaces were carried out by using ETD and BSED dedectors, the phases that coatings contain and their concentrations were determined by using X-ray diffraction (XRD) device.In conclusion, coatings 12, 18, 24, 48, 72, and 96-hour soaking period in the SBF are created, the necessary analyzes were carried out. The presence of hydroxyaphatite was determined in metallographic tests performed to the coatings obtained in SBS environment by keeping for 12, 18, 24, 48, 72 and 96 hours. The results of the mechanical tests, SBF coatings formed in the 12 and 18 hour periods, binding forces were not sufficient. According to the results from the mechanical tests, more successful results were obtained from the coatings obtained in SBS environment by keeping for 24 and 48 hours, to their counterparts. Besides, better results were obtained in scratch test for the coatings obtained in SBF environment and kept for 48 hours with respect to resistance to the adherence onto the surface, which is one of the most important characteristics. As a result of the research, all the values in blood plasma that were obtained first time by Pasinli et al. in worldwide literature were also achieved in this study. In this new buffer system, more successful results were obtained with SBS solution prepared with citric acid-sodium citrate buffer system that would not show any toxic effect on human body and stronger resistance values to adherence of coatings were also detected. Keywords: Biomaterials, Calcium Phosphate Coating (CaP), Apatite Coating, Hydroxyaphatite (HA), Synthetic Body Solution (SBS), Ti6Al4V, Implant