日本金属学会誌

J. Japan Inst. Metals, Vol. 51, No. 4 (1987),
pp. 309-318

Effects of Chemical Compositions and Heat Treatment on the Stress Corrosion Cracking Resistance of Precipitation Hardened Nickel Base Alloys in High Temperature Water

Toshio Yonezawa1, Noritake Yamaguchi2, Yasutaka Okada3 and Masaaki Igarashi3

1Takasago Research & Development Center, Mitsubishi Heavy Industries, Ltd., Takasago
2Kobe Shipyard & Engine Works, Mitsubishi Heavy Industries, Ltd., Kobe
3Technical Research Laboratories, Sumitomo Metal Industries, Ltd., Amagasaki

Abstract:

(1)  In order to develop a new gamma prime precipitation hardened nickel base alloy which satisfies the specified strength of Alloy X-750 and has a stress corrosion cracking resitance in high temperature pure water superior to the Alloy X-750, we have studied on the effect of alloying elements as C, Cr, Ti, Nb and Al and heat treatment on the tensile properties, the precipitation behaviour and the stress corrosion cracking resistance of the gamma prime precipitation hardened nickel base alloys at 360°C in simulated primary water, based on our previous studies on the correlation between the stress corrosion cracking resistance and the type, morphology and coherency of precipitates at the grain boundaries of the Alloy X-750.
As a result of the present study, it has been revealed that the gamma prime precipitation hardened nickel base alloy with C content higher than 0.02%, Cr content higher than 20% and similar contents of Ti, Nb and Al to those of the Alloy X-750 has an excellent stress corrosion cracking resistance.
(2)  In order to develop a new gamma double prime precipitation hardened nickel base alloy which satisfies the specified strength of Alloy 718 and has a superior stress corrosion cracking resistance in high temperature pure water to the Alloy 718, we have studied on the effect of alloying elements as C, Cr, Mo and heat treatment on the tensile properties, the precipitation behaviour and the stress corrosion cracking resistance of the gamma double prime precipitation hardened nickel base alloys at 360°C in simulated primary water. As a result of this study, it has been revealed that the gamma double prime precipitation hardened nickel base alloy with C content less than 0.07%, Cr content higher than 22%, Mo content higher than about 2.0%, higher Nb content and lower Ti and Al contents than those of Alloy 718 has an excellent stress corrosion cracking resistance.


(Received 1986/9/18)

Keywords:

stress corrosion cracking, grain boundary, nickel base alloy, nuclear power reactor, heat treatment, precipitation hardening, microstructure, coherency, tensile properties, high temperature pure water


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