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Journal of Materials Engineering and Performance, 2014, Volume 23, Issue 7, pp 2635-2640.
Markus Wohlschlögel, Rainer Steegmüller, Andreas Schüßler.
ADMEDES Schuessler GmbH, Pforzheim, Germany.
Abstract
Nonmetallic inclusions in Nitinol, such as carbides (TiC) and intermetallic oxides (Ti4Ni2O x ), are known to be triggers for fatigue failure of Nitinol medical devices. These mechanically brittle inclusions are introduced during the melting process. As a result of hot and cold working in the production of Nitinol tubing inclusions are fractionalized due to the mechanical deformation imposed. While the role of inclusions regarding Nitinol fatigue performance has been studied extensively in the past, their effect on Nitinol corrosion behavior was investigated in only a limited number of studies. The focus of the present work was to understand the effect of inclusion size and distribution on the corrosion behavior of medical-device grade Nitinol tubing made from three different ingot sources during different manufacturing stages: (i) for the initial stage (hollow: round bar with centric hole), (ii) after hot drawing, and (iii) after the final drawing step (final tubing dimensions: outer diameter 0.3 mm, wall thickness 0.1 mm). For one ingot source, two different material qualities were investigated. Potentiodynamic polarization tests were performed for electropolished samples of the above-mentioned stages. Results indicate that inclusion size rather than inclusion quantity affects the susceptibility of electropolished Nitinol to pitting corrosion.
Additional Information
Material experts at ADMEDES Schuessler, the leading global provider of finished Nitinol self-expandable implants to the medical device industry, have successfully demonstrated the impact of material impurities such as nonmetallic inclusions on the corrosion behavior of Nitinol tubing. This material is used for the production of self-expanding permanent implants like stents, heart valve frames and filters. Results of this research help to understand Nitinol corrosion behavior and to facilitate the safe design of medical devices.
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ADMEDES Schuessler is the leading global provider of finished Nitinol self-expandable implants to the medical device industry.
