Ni基のNi-Cr-Coオーステナイト合金の耐熱性について

Abstract

An investigation was made to evaluate the hightemperature properties of Ni-Cr-Co austenitic alloys containing up to 40% cobalt with chromium fixed at 20%. The alloys were examined at the 20% cold-rolled state after solution-quenching at 1200 deg C, and the water-quenched state at 1200 deg C after the cold-rolling. The results were: The alloys harden with the increase of the cobalt content because of the cold-rolling. The recrystallization temperature exists at 800 deg C, and appears to be a little lowered with an increase of the cobalt content. The bending creep ductility was measured by the deflection in the creep test, the values being smaller in the cold-rolled specimens than that of the water-quenched one at 1200 deg C after cold rolling. In the cold-rolled specimens, the deflections are very small, and the rupture times are short in alloys of low cobalt content. Among the water-quenched specimens at 1200 deg C after the cold rolling, the alloy containing about 30% cobalt, a minimum deflection, and a long rupture time were found. The weight increase from heating at 800 deg C for 100 hr in air is minimum in the 25% cobalt specimen. It can be said that the alloys containingmore » 20 to 30% cobalt are strongest in the high temperature strength. The addition of nitrogen hardens the alloys and raises the recrystallization temperature, and the oxidation resistivity at high temperatures is somewhat improved, although the rupture time in the bending creep test is shortened. (auth)« less