NITROGEN AND CARBON DIFFUSION IN WELDED-J OINTS OF CSN-12013 CSN-17241 AND CSN-12050 CSN-17241 STEELS

This paper deals with parallel nitrogen and carbon diffusion in the fe rrite/austenite steel welded joints at 500-degrees-C. Due to suitable choice of the chemical composition of the welded steels, i.e. the ferr itic carbon steels 12013 and 12050 enriched with nitrogen, and stainle ss steel 17241, it has been reached that nitrogen and carbon have diff used from ferritic steels into the austenitic one revealing Darken-lik e concentration redistribution. The evaluation of the measured concent ration curves N(i)(x, t), i = N, or C resp., yielded the diffusion coe fficients D(N), D(C) in the austenitic steel 17241, and the amplitudes of the concentration jumps at the weld interface. The data N(i)(x,t) measured in ferritic steels were, unfortunately, not evaluable due to low values and high scattering. The interpretation of the concentratio n jumps in terms of thermodynamic activity and Wagner's activity coeff icients made it possible to calculate the values of interaction coeffi cients epsilon(N)Cr, epsilon(C)Cr and epsilon(N)Ni. The good conformit y of our results with the data published by other authors [18, 19] may be considered, first, as a proof of a well developed experimental tec hnique used in our N, C concentration measurements, and, second, as a proof of the reliable applicability of our semiempirical theory descri bing the mutual interaction of interstitial and substitutional atoms i n Fe-gamma-solid solutions [5,8,10].