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Structure and properties of high temperature nitrided/oxided surface of Ni-Ti alloy

Jozef Lelatko 1Tomasz Goryczka 1Tadeusz Wierzchoń 2Henryk Morawiec 1

1. University of Silesia, Institute of Material Science, Bankowa 12, Katowice 40-007, Poland
2. Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland


Structure and properties of high temperature nitIn order to find new applications and enhance the performance of NiTi alloy, surface modifications is necessary condition for improving its biocompatibility. Nitride and oxide coatings, which are known from their low chemical reactivity, high hardness and good wear and corrosion resistance, were adopted for protecting the NiTi surface. The nitriding and oxidation processes reduce the nickel migration to the surface and improves the biocompatibility of the NiTi alloy. In the present work nearly-equiatomic NiTi (50,6 at.%Ni, Af =10°C) alloy was nitrided at 800oC using glow discharge technique. Additionally, at the end of the nitriding some amount of oxygen was added. Combination of nitriding and oxidiation of the NiTi surface produces nitride/oxide complex layer of a nanocrystalline structure. The average thickness of the obtained layer was about 0,55 μm. The nitrided layer contains nanocrystalline TiN phase. Adding the oxygen at the end of the nitriding process creates TiO2 phase on the top of the TiN layer. The layer of Ti2Ni phase creates the interface between nitrided/oxidized NiTi surface and β-NiTi matrix. Small amount of an amorphous phase, between the nano-grains of nitride and oxide phase, was identified. The potentiodynamical studies in Tyrod’s solution show good corrosion resistance of the nitrided/oxidized NiTi surface proving its high quality.


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Presentation: Poster at E-MRS Fall Meeting 2008, Symposium C, by Jozef Lelatko
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-09 14:31
Revised:   2009-06-07 00:48