Toshio Katagiri1, Kyoko Fujii1 and Nobujiro Takamoto1
1The Faculty of Engineering, Tokyo Metropolitan University, Tokyo
To study the effect of Ni and Cr on the formation of borider layer the gas boronizing of Fe-Ni alloy, Fe-Cr alloy and Ni with BCl3 and H2 were carried out in the temperature range from 700°C to 1000°C. From microscopic examination, X-ray diffraction, the measurement of microhardness and chemical analysis, the following results were obtained.
(1) The boride layer comprised of two layers of (Fe, Ni)B and (Fe, Ni)2B in Fe-Ni alloy, and FeB and Fe2B in Fe-Cr alloy.
(2) The boride layer of Ni was made up of three layers, in which NiB and Ni2B were observed.
(3) 40% or more addition of Ni accelerates the formation of the boride layer of Fe-Ni alloy, but its formation is impeded in Fe-Cr alloys as the addition of Cr is larger.
(4) Microhardness of the boride layers of Ni and permalloy is smaller than that of iron.
(5) The boride layers had a high corrosion resistance against corrosive action of 10%-and concentrated aqueous solution of HCl and H2SO4 but were badly damaged by 10%-and concentrated HNO3.
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