Fabrication of superhydrophilic surfaces for long time preservation on 316L stainless steel by ultraviolet laser etching

Due to the good biocompatibility, 316L stainless steel is widely used in the manufacture of medical instru-ments and human implants. The super hydrophilic 316L steel surface is used for reducing friction and adhe-sion. By choosing appropriate laser process parameters 316L steel surfaces with super-hydrophilic were ob-tained. The effects of laser process parameters including repeat frequency, pulse width, scanning speed, and the number of scanning were investigated to find the relationship between surface microstructure and wet-ting ability. To investigate the super-hydrophilic maintenance time on the textured surface, the textured sur-faces were preserved in ambident air, distilled water, and absolute ethanol. The results showed that by choosing appropriate laser process parameters surface with super-hydrophilicity can be maintained for 30 days.

Improving the Corrosion Resistance of AISI 316L Steel for Semiconductor Piping by Controlled Delta-Ferrite Content

This study evaluated changes in delta-ferrite content depending on the preheating of AISI 316L stainless steel. We also determined the reasons for the variation in delta-ferrite content, which affects corrosion resistance. Changes in delta-ferrite content after preheating was confirmed using a Feritscope, and the microstructure was analyzed using optical microscopy (OM). We found that the delta-ferrite microstructure size decreased when preheating time was increased at 1295 oC, and that the delta-ferrite content could be controlled through preheating. Potentiodynamic polarization test were carried out in NaCl (0.5 M) + H2SO4 (0.5 M) solution, and it was found that higher delta-ferrite content resulted in less corrosion potential and passive potential. To determine the cause, an analysis was conducted using energy-dispersive spectroscopy (EDS), which confirmed that higher delta-ferrite content led to weaker corrosion resistance, due to Cr degradation at the delta-ferrite and austenite boundaries. The degradation of Cr on the boundaries between austenite and delta-ferrite can be explained by the difference in the diffusion coefficient of Cr in the ferrite and austenite. A scanning electron microscopy (SEM) analysis of material used for actual semiconductor piping confirmed that corrosion begins at the delta-ferrite and austenite boundaries. These results confirm the need to control delta-ferrite content in AISI 316L stainless steel used for semiconductor piping.