Wear of Nitinol Wires as a Function of Nitinol Micro-Cleanliness and Surface Treatment

摘要

Nitinol is a material well-known for its use in the manufacturing of cardiovascular implants such as stents and heart valve frames. Beside laser-cut devices from nitinol tubing or sheets, there are now increasing numbers of medical devices made of nitinol wires by various textile processes such as weaving and braiding. For these wires, a variety of nitinol bulk material and surface finishing is used depending on the application. Unlike laser-cut devices, the nitinol wires of these woven or braided devices experience micro movements in-vivo. As a result, fretting damage may occur at crossover points of overlapping wires. It is well known that nitinol shows good wear resistance against fretting, sliding and rolling loads, especially compared to other medical implant materials [1-4]. Previously published data concluded that wear damage on electro-polished nitinol wires leads to changes in corrosion behavior but did not significantly decrease the pitting corrosion resistance [4]. Although this study provided insight into the effect of wear on corrosion resistance in electropolished nitinol wires, there are different surface finishes and micro-cleanliness of nitinol that have yet to be investigated.