TITLE:
Evaluation of the Surface of Nitinol after MR Polishing Process
AUTHORS:
Byung-Chan Kim, Jung-Won Lee, Seok-Jae Ha, Yong-Kyu Cho, Dong-Sung Kang, Myeong-Woo Cho
KEYWORDS:
Nitinol, MR Polishing, Corrosion Test, Residual Stress, Strain Hardening
JOURNAL NAME:
Journal of Applied Mathematics and Physics,
Vol.3 No.2,
January
30,
2015
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.