2008 Volume 72 Issue 8 Pages 610-616
Austenitic stainless steel (SUS304) specimens were sputter-etched by using argon ions, and the formation process of protrusions on the surface was investigated by changing the sputter etching time. In addition, tensile and bending tests of the specimens were carried out to examine whether the delamination between the protrusion and matrix occurs or not. When the sputter etching time is 0.9 ks, fine conical protrusions with diameter smaller than 2 μm are formed relatively homogeneously on the surface. When the sputter etching time is 1.8 ks, they grow to more than 5 μm. In some cases, the holes and cracks are formed on the wall of protrusions. When the sputter etching time is 3.6 ks, the protrusions grow further and occupy whole surface, and finally they collapse to form ring-shaped protrusions. The tensile test of the specimens with conical protrusions shows that, even at a fracture strain of 0.53, the shape of the cones is almost maintained and the plastic deformation occurs mainly in the region around them without delamination of the cones. Also in the bending test, the similar behavior to the tensile test is observed. The tensile test of the specimen with ring-shaped protrusions also shows that the deformation does not largely occur in the protrusion but occurs in the region outside of them. The reasons for the above characteristics seem to be that the outer shell of the protrusion with higher Cr content is strong and the protrusion grows from interior of specimen keeping high coherency to matrix.
