Improving the surface quality of “M” shape-link 316L stent by electrochemical polishing and investigating its mechanical properties

Additive manufacturing of metal stents (such as selective laser melting technology) may result in a relatively high surface roughness, which significantly affects the mechanical properties. To address the surface quality issue, this study employed electrochemical polishing technology to reduce the surface roughness of "M" shape-link 316L stent manufactured by selective laser melting technology, and evaluated the mechanical properties. The results showed that electrochemical polishing effectively removed the residual powder particles adhering to the surface of stent and the irregular surface protrusions formed during the manufacturing process, thereby reducing the surface roughness of 316L stents to less than 5 µm. Electrochemical polishing decreased the radial force of stents from 31.68 N to 19.71 N, but improved the axial compliance and flexibility. Its bending stiffness (10 N/mm) was reduced by 16 N/mm compared to 26 N/mm before polishing. The maximum load at the maximum deformation of 2.5 mm decreased by 4.8 N, thereby improving the compliance. Additionally, the maximum bending force (5.8 N) decreased by only 8.37 N, indicating that its resistance to bending fracture was sufficiently strong. Meanwhile, electrochemical polishing did not reduce the fatigue life of stents. After subjecting the polished stent to 1 × 10⁶ cycles of accelerated cyclic loading, the stent still retained its initial structural integrity, while both its peak pressure and overall pressure decreased, the specific reduction was only 12.5%. In conclusion, after electrochemical polishing, although a certain degree of stent rigidity was sacrificed, good flexibility and potential long-term implant durability were achieved.