  In this paper we report the effect of hydrogen on the structural properties
of AISI-H13 steel nitrogen-implanted samples in low oxygen partial pressure
atmosphere. The samples were implanted in a high vacuum chamber by using a
broad ion beam source. The H2+/N2+ ion composition of the beam was varied and
the surface composition studied in situ by photoemission electron spectroscopy
(XPS). The samples were also ex situ analyzed by X-ray diffraction and scanning
electron microscopy (SEM), including energy-dispersive spectroscopy
measurements. It was found that hydrogen has the effect of modifying the amount
of retained nitrogen at the surfaces. This result shows that hydrogen plays a
role beyond the well-established effect of oxygen etching in industrial
machines where vacuum is relatively less well controlled. Finally, an optimum
concentration of 20 to 40% [H2]/[H2+N2] ion beam composition was determined to
obtain maximum nitrogen incorporation on the metal surface.
