Abstract
Surfaces of solution-treated SUS304, SUS430, SCM435 and SKD5 steels were sputter-etched by Argon ions in an R.F. magnetron sputtering apparatus for 7.2, 14.4 and 28.8 ks. The observation using FIB and SIM shows that the conical carbides are formed on the surfaces of all the steels examined, and they are growing from the surface towards inside during sputter-etching. The carbides precipitate more along grain boundaries than in grains for SUS430 and SUS304 steels with low carbon content, while they uniformly precipitate in grains for SCM435 and SKD5 steels with high carbon content. The aspect ratios of conical carbides change within the range from 2 to 4 depending on sputter-etching time, sputter voltage, kinds of steels, size and density of carbides. The precipitation of carbides occurs under the balance of carbon diffusion velocity and sputter-etching rate. The size and density of conical carbides increase with increasing sputter-etching time. They eventually disappear, but many small carbides newly precipitate after long time sputter-etching.
