Transformation of expanded austenite to an amorphous ferromagnetic surface layer during laser carburization of austenitic stainless steel

Abstract The presented experiments that were carried out in order to advance the understanding of the transformation of expanded austenite into an amorphous ferromagnetic surface layer during laser carburization of austenitic stainless steel. Therefore laser carburized austenitic stainless steel was investigated by means of X-ray diffraction, Mossbauer spectroscopy, Rutherford backscattering and magneto-optical Kerr-effect. Five to seven sub-spectra attributed to different iron sites were resolved in the Mossbauer spectra for this iron-carbon austenite. The isomer shifts, the quadrupole splittings and in particular the subspectra fractions depend on the carbon content. The formation of an amorphous and soft ferromagnetic phase was found in the laser treated surface.