Effects of grain-boundary configuration on the creep rupture strength and grain-boundary sliding in austenitic heat-resisting steel.

概要

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The effect of grain-boundary configurations on the creep rupture strength was investigated using austenitic 21Cr-4Ni-9Mn (21-4N) steel in the temperature from 600 to 1000°C. The grain-boundary sliding was also examined on specimens crept at 700°C. Further, discussions were made on the relation between the amount of grain-boundary sliding and the initiation of grain-boundary cracks.The creep rupture strength was improved by serrated grain boundaries at temperatures above 600°C. The specimens with serrated grain boundaries had longer rupture lives than those with normal straight grain boundaries even at high temperatures around 1000°C.It was experimentally confirmed that both the life to crack initiation and the life of crack propagation increased by the serrated grain boundary at temperatures around 700°C, and that only the resistance to crack growth of the steel was improved by the strengthening at high temperatures above 900°C.The average amount of grain-boundary sliding in specimens during creep at 700°C was reduced by serrated grain boundary to about one-third or one fourth of that of the specimen with straight grain-boundary configuration. A good agreement was found between the experimental results on the critical amount of grain-boundary sliding for crack initiation and those predicted by the theory of triple point cracking.
The Iron and Steel Institute of Japanの論文