Creep rupture strength and grain-boundary sliding in austenitic 21 Cr-4Ni-9Mn steels with serrated grain boundaries |
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| Authors: | Manabu Tanaka Ohmi Miyagawa Tsuneaki Sakaki Hiroshi Iizuka Fumio Ashihara Dai Fujishiro |
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| Affiliation: | (1) Department of Mechanical Engineering for Production, Mining College, Akita University, 1-1, Tegatagakuen-cho, Akita 010, Japan;(2) Department of Mechanical Engineering, Faculty of Technology, Tokyo Metropolitan University, 2-1-1, Fukasawa, 158 Setagaya-ku, Tokyo, Japan;(3) Nittan Valve Corporation Ltd, 2-7-2, Yaesu, Chuou-ku, 104 Tokyo, Japan |
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| Abstract: | The effect of grain-boundary strengthening on the creep-rupture strength by modification of the grain-boundary configuration is studied using austenitic 21 Cr-4Ni-9Mn steel in the temperature range from 600 to 1000° C in air. Grain-boundary sliding is also examined on a steel with serrated grain boundaries during creep at 700° C. The improvement of creep-rupture strength by the strengthening of grain boundaries is observed at high temperatures above 600° C. The 1000 h rupture strength of steels with serrated grain boundaries is considerably higher than that of steels with straight grain boundaries, especially at 700 and 800° C. The strengthening by serrated grain boundaries is effective in retarding both the crack initiation and the crack propagation at 700° C, while it does not improve the life to crack initiation at 900° C. Grain-boundary sliding is considerably inhibited by the strengthening of grain boundaries at 700° C. The amount of it in steels with serrated grain boundaries is less than about one-third of that of steels with straight grain boundaries at the same creep strain. The stress dependence of grain-boundary sliding rate in the steady-state regime is also examined from the steels with these two types of grain-boundary configuration. |
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