日本金属学会誌

J. Japan Inst. Metals, Vol. 39, No. 3 (1975),
pp. 247-255

Diffusion Layers of Steel Surfaces Immersed in Fused Borax Baths Containing Various Kinds of Additives

Tohru Arai1, Masayoshi Mizutani1 and Noboru Komatsu1

1Toyota Central Research and Development Laboratories, Inc., Nagoya

Abstract:

To investigate the surface layers of steels immersed in various kinds of borax baths, steels were kept in the borax bath containing powders of pure metals, alloys, carbides, oxides and nitrides of such elements as Ca, Si, Al, Mn, R are earth, Mg, Zr, Ti, V, Nb, Cr, Zn, Co, Ni and Cu, and their surfaces and cross sections were examined by microscopy, X-ray diffraction and electron probe microanalyses.
The results obtained are summarized as follows.
(1) Iron boride layers were formed on 0.1%C steel specimens treated in the bath containing pure metal powders of Ca, Si, Al, rare earth, Mg, Zr or alloys powders.
(2) In the bath containing a large amount of Fe-Ti or Fe-Mn powders, Ti or Mn carbide layers were formed on high C steel specimens, while iron boride layers were formed on low C steel specimens.
(3) In the bath containing Fe-V or Fe-Nb powders, V or Nb carbide layers were formed on 0.1%C steel specimens.
(4) In the bath containing Fe-Cr powders, double layers of Cr carbide (outer) and Fe-Cr solid solutions (inner) were formed on 0.1%C steel specimens.
It may be concluded from the results that the tendency to form boride layers is greater in a fused borax bath containing metal powder with a higher free energy change (-Δ G) of the oxide formation than that of boron oxidation.


(Received 1974/08/2)

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