Effect of Plasma Spray and Surface Sealing Treatment of Ni-Ti Shape Memory Alloy Applying to Biomaterials

摘要

Sealing treatment for the porous titanium layers was performed in attempt to prevent cytotoxic nickel ions releasing from porous titanium plasma-sprayed Ni-Ti alloys due to the existence of chloride ions in the body liquid. Two types of sealants were used for this purpose, one was a group of biocompatible polymer resins and the other was metallic titanium. As polymer sealants, 4 kinds of resins (silicone, cyanoacryl resin, epoxy resin and polyamide resin) were used. The first three sealants were soaked into the porous coating layers after dilution by organic solvents, while the thermoplastic polyamide resin was melted and then penetrated into them. On the other hand, physical evaporation deposition (PVD) technique was employed for sealing with titanium metal. The effect of combination of the thickness of the plasma-sprayed layers and the amount of titanium deposited by PVD was investigated. The effectiveness of the sealants was evaluated by electrochemical polarization measurement. The adhesion test of the coating layer to the alloy substrate was also carried out. Among the polymer sealants, the polyamide resin showed excellent performance. As for the titanium PVD sealing, optimum combinations of the thickness of the coating layers and the amount of titanium PVD existed for both corrosion resistance and adhesion strength.