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KMID : 0384620090200020080
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Korean Journal of Medical Physics
2009 Volume.20 No. 2 p.80 ~ p.87
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Application of Ultrasonic Nano Crystal Surface Modification into Nitinol Stent Wire to Improve Mechanical Characteristics
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Kim Sang-Ho
Suh Tae-Suk
Lee Cahng-Soon
Park In-Gyu
Cho In-Sik
Pyoun Young-Shik
Kim Seong-Hyeon
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Abstract
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Phase transformation, superelastic characteristics and variation of surface residual stress were studied for Nitinol shape memory alloy through application of UNSM technology, and life extension methods of stent were also studied by using elastic resilience and corrosion resistance. Nitinol wire of ø1.778 mm showed similar surface roughness before and after UNSM treatment, but drawing traces and micro defects were all removed by UNSM treatment. It also changed the surface residual stress from tensile to compressive values, and XRD result showed less intensive austenite peak and clear martensite and additional R-phase peaks after UNSM treatment. Fatigue resistance could be greatly improved through removal of surface defects and rearrangement of surface residual stress from tensile to compressive state, and development of surface modification system to improve not only bio-compatability but also resistance to corrosion and wear will make it possible to develop vascular stent which can be used for circulating system diseases which run first cause of death of recent Koreans.
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KEYWORD
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Stent, Nitinol wire, Ultrasonic nano crystalline surface modification
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