X-ray stress analysis of neon implantation in laser-treated 304 stainless steel

Abstract

A powerful laser beam focused on an austenitic stainless steel introduces a considerable amount of tensile stress in the first 5 µm as measured by X-ray diffraction. Microscopic analysis reveals a solidification structure 50 µm deep with a strongly oriented grain size of less than 5 µm induced by the high self-quenching rate. Subsequent implantation with a rare gas introduces a layer of pressurized gas bubbles at a depth of only 80 nm and a deformation layer as far down as 250 nm. Although the shear stress at the bubble-matrix interface transforms the metastable f.c.c. crystal structure locally into a martensitic b.c.c. phase, the actual transformed fraction is small. Mainly the implantation but also the transformation add in reducing the tensile stress by as much as 25% in total.