Formation of Fine Protrusions on Steel Sheets and Wires by Sputter Etching

Abstract

Six kinds of steels with various thickness smaller than 3mm and SUS304 steel wires with 0.5 and 0.2 mm diameter were etched by argon ion sputtering at a radio frequency power of 100-350W for 0.9-19.8ks. Cone-shaped protrusions with various sizes smaller than 5μm were formed on the surface of SK120, SUS304 and SKD61 steel sheets. These protrusions were formed from the bottom of pillar-shaped carbides that precipitate perpendicular to the surface. When the sheet thickness is very small, the conical protrusions were not formed, but the column- or ringshaped protrusions with various sizes smaller than 1μm were formed on the surface of SUS304, SUS316, SUS316L and SKD61 steels. The reason will be that the precipitation of fine pillar-shaped carbides occurs densely due to a small temperature gradient in the thickness direction and the conical protrusions quickly decay to the column- or ring-shaped protrusions. Also for the SUS304 wire, the fine column- or ringshaped protrusions were formed over whole of the surface due to a roundabout of plasma. The sheets and wires with not only the cone-shaped protrusions but also the column- or ring-shaped ones will give wide and flexible applicability to machine parts and structures revealing many functions.