Fabrication of Nanoprotrusion Surface on AISI 316 Stainless Steel via Ar–N₂ Plasma Etching

抄録

Argon (Ar) plasma etching of stainless steel is known to form a unique surface texture consisting of nanopillars of several hundred nanometers due to the use of carbide precipitates as a template. The present study demonstrates that adding a small amount of nitrogen (N₂) gas to Ar plasma discharge gas reduces the pillar size and enhances the pillar density, thereby resulting in a densely arranged nanoprotrusion surface. Admixing 1% N₂ to the discharge gas decreased the height of each nanopillar to approximately a quarter of its original height. A further increase in N₂ gas hardly changed the size of the nanoprotrusions, yet its number density increased up to 5% N₂ addition. Admixed N₂ gas generates N₂⁺ species in the plasma, which form tiny chromium nitride (CrN) precipitates on a stainless steel surface. These CrN precipitates have become an alternative template for plasma etching. Nanoprotrusion surfaces are expected to improve the tribological properties of stainless steel surfaces; thus, the introduced process has potential for industrial applications.

Fig. 2 (a) Schematic illustration defining height, base diameter, cap diameter, and density of nanopillars and nanoprotrusion. (b) Height, base diameter, and cap diameter and (c) number density of the nanopillars across the different N₂ gas concentrations.