Cr3C2-Ni系焼結合金の金属相の研究

概要

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Based on the oxidation mechanism of the alloy, auther considered previously that Ni-Cr alloy is formed in binder phase and it may be responsible for a good corrosion-resistance and oxidation-resistance. In the present work, process forming the alloy binder during the sintering was investigated by X-ray diffraction and thermomagnetic analysis. During the sintering below eutectic temperature, Cr3C2 decomposed into Cr7C3, Cr and carbon and the resulting Cr7C3 or Cr diffused rapidly in Ni phase compared with Cr3C2. As a result of such reaction the Ni-Cr alloy binder is formed, at the same time free carbon is formed in binder phase. In the specimens sintered above eutectic temperature, it was also found on the basis of the lattice constant and Curie temperature of Ni solid solution containing Cr3C2 that the alloy phase with the properties as a nichrome is formed in the binder. Such binder phase was heterogeneous. Formation of the alloy binder phase is desirable for the corrosion-resisting and the oxidation-resisting properties of the alloy but formation of graphite result a poor mechanical strength. Therefore elimination of graphite is important practically.
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