ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Nitrogen Dissociation Rate at Solid Surface of Ferrous Alloys
Hideki Ono-NakazatoAkitoshi MatsuiTateo Usui
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2002 Volume 42 Issue 3 Pages 229-234

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Abstract

The nitrogen dissociation rates at the surface of solid iron–M (M: Si, Al, Mn, Cr, and Ti) alloys have been measured by an isotope exchange technique at temperatures ranging from 1 473 to 1 798 K. From the present results, the rate constant of nitrogen dissociation at the surface of pure solid iron is derived as 1.97×10-5[mol/(cm2 · s · atm)] at 1 773 K and the apparent activation energies for the nitrogen dissociation at the surfaces of δ-Fe and γ-Fe ([mass ppm O]=10.3, [mass ppm S]=7) at PN2=0.05 (atm) are calculated as 127 and 162 (kJ/mol), respectively. The effects of the alloying elements on the nitrogen dissociation rate at the surface of solid iron have the same tendency as those at the surface of liquid iron investigated previously by a similar method to the present study; the nitrogen dissociation rate is increased by the addition of Mn, Cr, or Ti and is decreased by the addition of Si or Al. The degree of the effects of increasing or decreasing the rate by the alloying elements for the solid iron is found to be smaller than that for the liquid iron.

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