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Evaluation of the Surface of Nitinol after MR Polishing Process

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http://www.scirp.org/journal/PaperInformation.aspx?PaperID=53682#.VM80qizQrzE

Author(s)   
Byung-Chan Kim1, Jung-Won Lee1, Seok-Jae Ha1, Yong-Kyu Cho1, Dong-Sung Kang2, Myeong-Woo Cho1

Affiliation(s)
1Department of Mechanical Engineering, Inha University, Incheon, Republic of Korea.
2WISYS, Gunpo-si, Republic of Korea.

ABSTRACT
Nitinol is used in various industries, especially for biomaterials. Generally, the surface integrity of sub-micron level and non-surface flaw is required in nitinol for biomaterial. However, surface flaws, such as scratches, pits, and residual stress, can occur on the polished surface, and it is difficult to remove these surface flaws. The corrosion is accelerated continuously and causes bad influence in the body. Therefore, in this study, conventional polishing and MR polishing were used to minimize the corrosion and residual stress when the nitinol is used as biomaterial. X-ray diffraction and Tafel extrapolation were used to investigate the residual stress and the corrosion, and the strain hardening was investigated by nanoindentation. Surface integrities were also evaluated by SEM image and surface roughness results. As a result, the increased residual stress in conventional polishing was decreased by MR polishing. The result of corrosion test was improved from ?301 mV to ?280 mV. The residual stress was improved from ?38.18 MPa to ?31.17 MPa. Finally, it is certified that MR polishing can be used to minimize surface flaws and to improve the corrosion properties.

KEYWORDS
Nitinol, MR Polishing, Corrosion Test, Residual Stress, Strain Hardening

Cite this paper
Kim, B. , Lee, J. , Ha, S. , Cho, Y. , Kang, D. and Cho, M. (2015) Evaluation of the Surface of Nitinol after MR Polishing Process. Journal of Applied Mathematics and Physics, 3, 208-217. doi: 10.4236/jamp.2015.32031.

References
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[2]Shabalovskava, S. (2002) Corrosion and Biocompatibility Aspects of Nitinol as an Implant Material. Bio-Me. Mater. Eng., 12, 69-109.
 
[3]Wang, J., Li, N., Rao, G. and Han, E. (2007) Stress Corrosion Cracking of NiTi in Artificial Saliva. Dent. Mater., 23, 133-137. http://dx.doi.org/10.1016/j.dental.2006.01.001
 
[4]Deville, S. (2006) Influence of Surface Finish and Residual Stresses on the Ageing Sensitive of Biomedical Grade Zirconia. Bio. Mater., 21, 2186-2192.
 
[5]Lee, D.J. and Choi, H.S. Introduction to Electrochemistry. Ajin Publisher.
 
[6]Liu, C. (2010) In Vitro Electrochemical Corrosion Behavior of Functionally Graded Diamond-Like Carbon Coatings on Biomedical Nitinol Alloy. Thin Solid Films, 496, 457-462. http://dx.doi.org/10.1016/j.tsf.2005.09.109
 
[7]Nor Asma, R.B.A. (2011) Study on the Effect of Surface Finish on Corrosion of Carbon Steel in CO2 Environment. J. of App. Sci., 11, 2053-2057. http://dx.doi.org/10.3923/jas.2011.2053.2057               eww150202lx
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