Oxidation of an NiTi alloy

✍ Scribed by C.-M. Chan; S. Trigwell; T. Duerig

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 491 KB
• Volume: 15
• Category: Article
• ISSN: 0142-2421
• DOI: 10.1002/sia.740150602

✦ Synopsis

Abstract

In this study, the oxidation of the surface of a 50/50 (at.%) NiTi alloy was studied by XPS, AES and SEM. Samples of the NiTi alloy were oxidized at 23°C and high temperatures at an oxygen pressure of 10^−4^ Torr and in atmosphere. At 10^−4^ Torr of O~2~ and 23°C, titanium was oxidized preferentially while nickel remained in the metallic form even after 40 min of exposure. At the same oxygen partial pressure and 400°C, a mixture of TiO~x~, Ti~2~O~3~ and TiO~2~ was formed, and nickel remained metallic. Eventually, after 40 min of O~2~ exposure, the whole surface was covered with a layer of TiO~2~. In atmosphere and at 23°C, titanium again was oxidized preferentially, but NiO was detected on the surface after the first minute of air exposure. At a higher temperature of 450°C, areas comprising a mixture of NiO and TiO~2~, and areas consisting of TiO~2~ only were found. Below the top surface layer, a complete layer of TiO~2~ was detected. Underneath the TiO~2~ layer, a nickel‐rich layer was present.