Surface Hardening by Nitration for Some Stainless Austenite Steel Types

Résumé

Stainless austenite steel types have a good resistance to corrosion in different natural, industrial environments but their hardness and mechanical resistance are low enough. In order to assure an increased resistance to abrasion it is necessary to increase also the surface hardness. This thing is possible if the nitrogen concentration in the surface layer is increased by means of nitration.
The researches made on stainless austenite steel types pointed out a strong hardening tendency for the major part of steel types except for steel type 2CuMoNiCr200. The austenite in this has a very high degree of stability as a result of high content of alloying elements. When the nitrogen is diluted, the hardness is more reduced. Hardness strong increase in the other steel types is determined by complex nitrides separations favoured by nitrogen diffusion and increase of its concentration in the surface layer. The thickness of the hard layer increases depending on the period of nitration process from one hour to 3 hours and is influenced also by the characteristics of each sample.