NiAl-X合金/酸化皮膜界面の微細構造に及ぼす添加元素の影響

概要

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In order to clarify spalling mechanism of oxide scale on NiAl, microstructures in the vicinity of NiAl-X(Hf, Zr)/oxide scale interfaces were observed by using TEM. The oxidation tests were done at 1373 K in air for up to 360 ks. In NiAl, many voids were formed at the substrate/Al2O3 interface, leading to spalling of the alumina scale. On the other hand, addition of Hf or Zr to NiAl leads to suppression of the void formation, resulting in prevention of spalling of alumina scale. In addition, a Ni-Al-O layer tends to be formed at the interface in NiAl. This demonstrates appreciable increase in oxygen partial pressure and nickel activity at the interface. In fact, GDS measurements indicated depression of the Al concentration in the substrate close to an alumina scale. Consequently, it was speculated that the addition of Hf or Zr leads to increase in diffusivity of Al in the substrate and suppression of void formation at NiAl/alumina scale, resulting in prevention of spalling of an alumina scale.
2006-03-24