Characterization of long term aged martensitic stainless steels
- Toshiba Corp., Yokohama (Japan)
Types CA6NM (13Cr), 431 and 630 (17Cr) were aged at 400{degrees}C and 350{degrees}C for up to 10000 hours, and their hardness change and SCC susceptibility in 288{degrees}C water were investigated. Hardness of the alloys increased with aging. Hardness of type 431 aged at 400{degrees}C for 10000 hours exceeded 340 in Hv, over which tempered martensitic stainless steels had become susceptible to SCC, and showed high SCC susceptibility. Type 630 had high SCC susceptibility in before and after aged condition, and the hardness in both conditions was more than Hv 340. Therefore, hardness was considered to be a parameter which could describe the SCC susceptibility of martensitic stainless steels. Using activation energy for hardness change 105-125kJ/mol and the critical hardness level Hv=340, the marginal life-time for martensitic stainless steels at 288{degrees}C was estimated. Predicted life of type 431 and CA6NM were around 10{sup 5} hours and more than 10{sup 6} hours, respectively. Activation energies obtained for toughness change and hardness change were different. Consequently, it was concluded that at least two factors should be taken into consideration for determining the total life-limit for usage of martensitic stainless steels in the light water reactor environment. The meaning of the existence of critical hardness for SCC susceptibility has been also discussed. Higher than 340 in Hv, yield strength and strain for uniform deformation showed a tendency of saturation. Therefore, it was conjectured that some extreme internal strain level, which may change the plastic deformation manner, is the absolute factor for determining the SCC susceptibility of the alloys in high temperature water.
- OSTI ID:
- 48063
- Report Number(s):
- CONF-910808-; TRN: 95:011494
- Resource Relation:
- Conference: 5. international symposium on environmental degradation of materials in nuclear power systems - water reactors, Monterey, CA (United States), 25-29 Aug 1991; Other Information: PBD: 1992; Related Information: Is Part Of Proceedings of the fifth international symposium on environmental degradation of materials in nuclear power systems - water reactors; PB: 995 p.
- Country of Publication:
- United States
- Language:
- English
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