Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Experimental Determination of Isothermal Section at 1 273 K in the Ternary Ni-Cr-N System
Nagato ONOMasanori KAJIHARAMakoto KIKUCHI
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1991 Volume 77 Issue 9 Pages 1473-1480

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Abstract

An isothermal section of the equilibrium phase diagram in the ternary Ni-Cr-N system was experimentally determined at 1 273 K. Binary Ni-Cr alloys with chromium concentration from 20 to 79 mass% were nitrided in pure nitrogen gas under various pressures between 10 and 96 kPa at 1 423 or 1 523 K. The ternary Ni-Cr-N alloys prepared by the nitriding were equilibrated at 1 273 K for time varying between 2.0 × 106 and 3.7 × 107 s. The concentration of nickel and chromium of each phase in the equilibrated alloys was determined by conventional electron probe microanalysis. Nitrogen in solid solution phases and nitrides was analyzed by a refined method of electron probe microanalysis, which has been recently established by the present authors.
A nitride with the metal-atom arrangement of β manganese, which is designated as a π phase, was found to be in equilibrium with a nickel-rich fcc-γ phase, a chromium-rich bcc-α phase, and a di-chromium nitride, which is designated as an ε phase. The chemical compositions of the π and ε phases observed in the present work led to the formulae of Cr12(Ni0.94-0.97 Cr0.06-0.25)8 N3.9-4.2 and (Cr0.99 Ni0.1)2 N0.80-0.97, respectively. The π phase became unstable above 1 473 K. This explains a previous unsuccessful attempt to make the Ni-Cr-N ternary π phase by replacing molybdenum in Mo12Ni8N4 with chromium.

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© The Iron and Steel Institute of Japan
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