Influence of microstructure on the corrosion behavior of nitrocarburized AISI H13 tool steel obtained by pulsed DC plasma

The influence of microstructure on the corrosion behavior of pulsed plasma nitrocarburized AISI H13 tool steel in NaCl 0.9 wt/V % solution is reported. The samples were prepared with different nitrocarburizing treatment times using a constant [CH4/H-2+N-2] gaseous mixture by a DC pulsed plasma system. The microstructure of the nitrocarburized layers was analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. The corrosion behavior was evaluated by potentiodynamic polarization experiments. The nitrocarburizing process considerably improves the corrosion resistance of the material in a NaCl environment as compared to the untreated H13 steel. The modified surface layer mainly consisting of epsilon-Fe2-3(C,N) and gamma'-Fe4N phases confers this outstanding behavior. The corrosion resistance dependence on specific nitrocarburizing processes is reported and the role of the surface porosity is discussed. (c) 2008 Elsevier B.V. All rights reserved.