Experimental data on the growth rate of ’ and  layers which formed during the gaseous nitriding of Fe were assessed by applying recent thermodynamic descriptions of the Fe-N system. The atomic mobility of N in ’ was found to be approximately independent of the composition, and could be described by:

D (m2/s) = 2.7 x 10-10exp[-88.3(kJ/mol)/RT]

at temperatures of between 777 and 843K. The atomic mobility of N in  was assumed to be independent of the concentration, and could be described by:

M (m2/sJ) = 4.6 x 10-13exp[-80.7(kJ/mol)/RT]

at temperatures of between 848 and 1300K.

H.Du, J.Agren: Zeitschrift für Metallkunde, 1995, 86[8], 522-9