オーステナイト耐熱鋼のクリープ破断特性におよぼす粒界反応の影響
1979 年 65 巻 7 号 p. 939-948
詳細
1979 年 65 巻 7 号 p. 939-948
The effect of the grain boundary reaction on the creep rupture properties has been investigated for an austenitic engine valve steel (21-4N) at 600°-800°C.
The creep ductility as well as the minimum creep rate increased with increasing amount of the reaction but its increase came to a halt above about 30 per cent of the reaction. The creep rupture strength was remarkably improved by very small amount of the reaction, and the steel with about 8 per cent of it had the maximum strength and the favorable ductility, while more than about 8 per cent of it rather decreased the rupture strength in spite of the increased ductility. A noticeable notch strengthening was observed on the steels with more than about 30 per cent of the reaction, but the steels with poor ductility were apt to be notch weakened.
It was found by means of both optical and scanning electron microscopies that the increase in strength and ductility was resulted from the retardation of the grain boundary sliding and the occurrence of the ductile intergranular fracture owing to the reaction.
