Ageing-resistant bonding on stainless steels by laser treatment followed by flame silicatization

In many technological areas, especially in the medical sector, stainless steel parts are being used due to their longevity, good biocompatibility, and high resistance against hygrothermal conditions related to sterilization procedures. Numerous medical products include an adhesive bond that have to reliably withstand these harsh conditions encountered, for example, during autoclaving. However, well established adherent treatment procedures require hazardous chemicals or are not suitable for small fragile parts, for example, components of endoscopes. Therefore, efficient alternatives are necessary. This publication thus presents a combined surface treatment procedure of laser ablation/structuring and flame silicatization. The investigations demonstrate that the resistance to hygrothermal ageing of stainless steel adhesive joints can be significantly increased by pulsed laser irradiation. However, a drastic improvement can only be achieved when the laser fluence exceeds a certain threshold value and, in addition, a nanoporous oxide layer with a reduced chromium content is formed. For substrates of this surface type, ageing resistance can be increased even further by subsequent flame silicatization treatment. The combined methods have proven to be superior as compared to well established processes like sand blasting and coating or corundum blasting.