Nitrogen transport during plasma ion nitriding of austenitic stainless steel - the role of the native surface oxide layer


Nitrogen transport during plasma ion nitriding of austenitic stainless steel - the role of the native surface oxide layer

Parascandola, S.; Kruse, O.; Richter, E.; Möller, W.

Austenitic stainless steels are widely used due to their advantageous combination of properties as ductility, strength and excellent corrosion resistance. However, due to their moderate hardness they are not suited for abrasively stressed parts. Hence, the market potential of austenitic stainless steels could be greatly enhanced by a process that allows surface hardening without negatively affecting the other properties. Standard techniques as heat treatment, carburizing and conventional nitriding fail. Recently it has been shown that ion nitriding at moderate temperature is a promising candidate for surface hardening austenitic stainless steels. Surface hardness increased by factors of 4 to 5 leading to wear resistance increases by more than two orders of magnitude have been achieved without compromising the excellent corrosion resistance. It has been reported that the nitriding velocity depends on the ion energy and on the current density and that the passivating surface oxide layer of the austenitic stainless steels may play an important role. In a systematic study the influence of the surface oxide layer on the nitriding efficiency of ion nitriding austenitic stainless steel at moderate temperatures is analyzed by determining the retained nitrogen dose for fixed process times and temperatures but different oxygen partial pressures, ion current densities and ion energies. Additionally, for some selected process parameters during processing, the composition of the near surface region (down to 150nm) regarding the nitrogen, the carbon and the oxygen content is obtained by an in situ experiment.

  • Lecture (Conference)
    Int. Conf. on Metallurgical Coatings and Thin Films, San Diego, April 27 - May 1, 1998

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Publ.-Id: 2263