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 1986.    ----------------.  [KRICHEVSKII, I. R., AND KHAZANOVA, N. E.]  [Nitriding of Iron.]  Doklady Akad. Nauk. S.S.S.R., vol. 71, 1950, pp. 481-484; Chem. Abs., vol. 44, 1950, p. 10,631.

        Specimens of Fe were nitrided at 375°, 400°, 450°, and 500° at atmospheric pressure in NH3-H2 mixtures, the NH3 content ranging 35-65%.  The nitriding reaction stopped almost completely as a limiting N2 content in the Fe was approached, the final N2 content increasing with increase in temperature or NH3 concentration.  Nitriding is the result of 2 opposing reactions:  (1) 2 NH3+2xFe→2 FexN+3 H2, and (2) 2 FexN→2xFe+N2.  Reaction (1) is limited by rate of diffusion of N2 through Fe and Fe nitrides, and because of the low rate of diffusion through Fe nitrides, the reaction slows down as the nitrides increase until equilibrium between the 2 reactions is attained.

                  KRIEG, A.  See abs. 43a, 44, 46, 48, 49.