The investigation of the surface characterization, corrosion and mechanical properties, of REX-734 and Ni-Ti alloys by using different bioceramic coatings

REX-734 and NiTi alloy substrates which are used as metalic implant in biomedical applications were coated by Hidroksiapatit (HA) and BioGlass (BG) based bio-ceramics by using sol-gel method. In REX-734 substrates; HA, HA-SiO2, HA-Ag, HA-Zr, HA-Se/Chitosan, BG-Zr, also NiTi substrates; HA, HA-Ag, HA-Se/Chitosan and BG-Ag surface coatings were carried out. Different bioceramic coatings on REX-734 and NiTi substrates were obtained and analyzed via adhesion, corrosion, hardness and cell viability. The surface coatings were characterized by SEM, EDX and XRD analysis. Porous structure and low crack density was achieved which are important in the interaction between tissue and implant. The sintering temperature and sintering rate was found to have a significant effect on strength and adhesion of the coatings. Adhesion strength of HA based coatings was found to be higher than BG based ones on both REX734 and NiTi substrates. It was determined that adhesion strength of HA increased due to Zr and Ag additives, although Se/Chitosan addition, only small decrease in adhesion strength is achieved. It was observed that the corrosion caused to degradation of spherical structure and led to pitting formation on all coatings. It was also determined that the addition of SiO2 and Zr increased the corrosion resistance of REX-734 coated samples. The highest corrosion resistance was achived on HA-Ag coated NiTi substrates and such coating materials improved the bone cell vitality of both, REX-734 and NiTi substrates. Cell viability structures of HA-Se/Chitosan dupleks coatings were observed to exhibit better vitality than the single layer HA coatings. Keywords: Bioceramics, HA Coating, Sol-gel, REX-734, Ni-Ti, Corrosion, Adhesion, Cell Viability