Surface Machining of Stainless Steel Cardiovascular Stents by Fluid Abrasive Machining and Electropolishing

Abstract

The typical manufacturing process of tubular metallic cardiovascular stents includes laser cutting, sand blasting, acid pickling, electropolishing, surface passivation, and cleaning. The most commonly used material for cardiovascular stents is stainless steel, such as SUS 304 and SUS 316. After the laser cutting process, substantial improvement of the stent surface morphology is required to obtain acceptable surface roughness, edge roundness, and reduction of surface defects. This study focuses on a novel post-treatment method of fluid abrasive machining to replace the conventional sand blasting and acid pickling processes, resulting in the surface smoothness and edge roundness that are suitable for cardiovascular stent fabrication. The dross deposition and striations retained after laser cutting can be significantly removed with fluid abrasive machining. Both DC current and pulse current electropolishing techniques were performed to attain the final surface and structural quality after the fluid abrasive machining process. The experimental results show that an extremely fine surface roughness and a satisfactory edge roundness can be achieved for stents through both DC current and pulse current electropolishing. The pulse electropolishing process is more effective than the DC current electropolishing process to achieve edge roundness with less weight removal.