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

 

Table 126

Lattice Diffusion Parameters for 22P in Fe-Mo

 

P (at%)

Mo (at%)

Phase

Do (m2/s)

E (kJ/mol)

-

-

paramagnetic

2.87 x 10-2

271

-

-

ferromagnetic

1.38 x 101

332

0.16

-

paramagnetic

3.76 x 10-2

275

0.16

-

ferromagnetic

1.08 x 10-1

288

0.18

-

paramagnetic

2.55 x 10-3

247

0.18

-

ferromagnetic

1.06 x 103

359

0.38

-

paramagnetic

8.87 x 10-3

259

0.38

-

ferromagnetic

4.90 x 100

316

0.14

0.29

paramagnetic

4.16 x 10-5

215

0.14

0.29

ferromagnetic

3.23 x 106

434

0.17

0.98

paramagnetic

1.30 x 10-2

267

0.17

0.98

ferromagnetic

6.00 x 109

496

 

 

Table 127

Grain Boundary Diffusion Parameters for 22P in Fe-Mo

 

P (at%)

Mo (at%)

Temperature (K)

Do (m2/s)

E (kJ/mol)

-

-

1018-1153

3.03 x 10-9

218

0.16

-

974-1155

4.30 x 10-12

153

0.18

-

974-1153

3.36 x 10-11

168

0.38

-

932-1153

2.31 x 10-10

192

0.14

0.29

1055-1155

2.06 x 10-12

151

0.14

0.29

932-1018

4.26 x 101

415

0.17

0.98

1055-1155

2.42 x 10-9

218

0.17

0.98

932-1018

7.74 x 105

505