極低酸素ポテンシャルの気相中におけるNi-Cr 合金の応力下酸化挙動
Oxidation behavior under stress of Ni-Cr alloys in gas phase under extremely-low oxygen potential
著者:
阿部 博志 Hiroshi ABE 渡辺 豊 Yutaka WATANABE
発刊日:
公開日:
grain boundaryNi-Cr alloyoxidationoxygen partial pressuresuperheated steam
概要
Oxidation behavior and cracking susceptibility of the Ni-Cr alloys (Ni-14Cr, Ni-22Cr and Ni-30Cr) under extremely-low oxygen partial pressure have been investigated by experiments used as plate specimen and Reverse U-Bend (RUB) specimen for 750 hours at 400 °C in two kinds of gas system (inert gas and dry steam) under various oxygen potential (Ni stable, Ni/NiO equilibrium and NiO stable).The Ni-Cr alloys cracked along grain boundary both in inert gas system (with trace O2, without H2O ) and in hydrogenated steam. The cracking susceptibility was confirmed in near Ni/Nio equilibrium in hydrogenated steam as contrasted with higher oxygen potential in inert gas system. This result shows that potential range for the cracking susc eptibility seemed to be different between the two kinds of gas system. Cracking severity was highest for Ni-14Cr and lowest for Ni-30Cr both in inert gas and steam. But even Ni-30Cr was not immune to IG cracking in steam near Ni/NiO equilibrium.
