  The microstructural development in H13 tool steel upon nitriding by an ion
beam process was investigated. The nitriding experiments were performed at a
relatively low temperature of about 400\deg C and at constant ion beam energy
(400 eV) of different doses in a high-vacuum preparation chamber; the ion
source was fed with high purity nitrogen gas. The specimens were characterized
by X-ray photoelectron spectroscopy (XPS), electron probe microanalysis (EPMA),
scanning and transmission electron microscopy (SEM and TEM), and grazing
incidence and Bragg-Brentano X-ray diffractometry. In particular, the influence
of the nitrogen surface concentration on the development of the nitrogen
concentration-depth profile and the possible precipitation of alloying element
nitrides are discussed.
