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Title: Improvement of High Temperature Mechanical Property by Precipitation Hardening of Reduced Activation Ferritic/Martensitic Steels

Abstract

Reduced Activation Ferritic/Martensitic steels (RAFs) are leading candidates for blanket and first wall structures of the D-T fusion reactors. Recently, in order to achieve better efficiency of energy conversion by using RAFs in advanced blanket systems, improvement of high temperature mechanical property of RAFs is desired. In this work, experimental alloys, FETA-series (Fe-Ta-C or N) steels, were prepared to observe precipitation hardening mechanism by MX-type particles at elevated temperatures in detail. According to the results, innovative improvement of creep property can be achieved by applying of precipitation hardening by very fine TaX (X=C, N) particles. With increasing tantalum content, finer dispersion of MX-type particles, dislocation structures and sub-grain structures were observed by TEM (Transmission Electron Microscopy). These fine structures contributed to the improvement of creep property.

Authors:
 [1];  [2];  [2];  [3];  [4];  [2]
  1. Graduate school of Energy Science, Kyoto University (Japan)
  2. Institute of Advanced Energy, Kyoto University (Japan)
  3. National Defense Academy (Japan)
  4. Muroran Institute of Technology (Japan)
Publication Date:
OSTI Identifier:
20849512
Resource Type:
Journal Article
Resource Relation:
Journal Name: Fusion Science and Technology; Journal Volume: 44; Journal Issue: 1; Other Information: Copyright (c) 2006 American Nuclear Society (ANS), United States, All rights reserved. http://epubs.ans.org/; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CREEP; DISLOCATIONS; EFFICIENCY; ENERGY CONVERSION; FERRITIC STEELS; FINE STRUCTURE; FIRST WALL; MARTENSITIC STEELS; PARTICLES; PRECIPITATION HARDENING; TANTALUM; THERMONUCLEAR REACTOR MATERIALS; THERMONUCLEAR REACTORS; TRANSMISSION ELECTRON MICROSCOPY

Citation Formats

Sakasegawa, H., Kohyama, A., Katoh, Y., Tamura, M., Khono, Y., and Kimura, A. Improvement of High Temperature Mechanical Property by Precipitation Hardening of Reduced Activation Ferritic/Martensitic Steels. United States: N. p., 2003. Web.
Sakasegawa, H., Kohyama, A., Katoh, Y., Tamura, M., Khono, Y., & Kimura, A. Improvement of High Temperature Mechanical Property by Precipitation Hardening of Reduced Activation Ferritic/Martensitic Steels. United States.
Sakasegawa, H., Kohyama, A., Katoh, Y., Tamura, M., Khono, Y., and Kimura, A. 2003. "Improvement of High Temperature Mechanical Property by Precipitation Hardening of Reduced Activation Ferritic/Martensitic Steels". United States. doi:.
@article{osti_20849512,
title = {Improvement of High Temperature Mechanical Property by Precipitation Hardening of Reduced Activation Ferritic/Martensitic Steels},
author = {Sakasegawa, H. and Kohyama, A. and Katoh, Y. and Tamura, M. and Khono, Y. and Kimura, A.},
abstractNote = {Reduced Activation Ferritic/Martensitic steels (RAFs) are leading candidates for blanket and first wall structures of the D-T fusion reactors. Recently, in order to achieve better efficiency of energy conversion by using RAFs in advanced blanket systems, improvement of high temperature mechanical property of RAFs is desired. In this work, experimental alloys, FETA-series (Fe-Ta-C or N) steels, were prepared to observe precipitation hardening mechanism by MX-type particles at elevated temperatures in detail. According to the results, innovative improvement of creep property can be achieved by applying of precipitation hardening by very fine TaX (X=C, N) particles. With increasing tantalum content, finer dispersion of MX-type particles, dislocation structures and sub-grain structures were observed by TEM (Transmission Electron Microscopy). These fine structures contributed to the improvement of creep property.},
doi = {},
journal = {Fusion Science and Technology},
number = 1,
volume = 44,
place = {United States},
year = 2003,
month = 7
}
  • Reduced-activation ferritic-martensitic (RAFM) steels, candidate structural materials for fusion reactors, have achieved technological maturity after about three decades of research and development. The recent status of a few developmental aspects of current RAFM steels, such as aging resistance, plate thickness effects, fracture toughness, and fatigue, is updated in this paper, together with ongoing efforts to develop next-generation RAFM steels for superior high-temperature performance. Additionally, to thermomechanical treatments, including nonstandard heat treatment, alloy chemistry refinements and modifications have demonstrated some improvements in high-temperature performance. Castable nanostructured alloys (CNAs) were developed by significantly increasing the amount of nanoscale MX (M = V/Ta/Ti,more » X = C/N) precipitates and reducing coarse M 23C 6 (M = Cr). Preliminary results showed promising improvement in creep resistance and Charpy impact toughness. We present and compare limited low-dose neutron irradiation results for one of the CNAs and China low activation martensitic with data for F82H and Eurofer97 irradiated up to ~70 displacements per atom at ~300–325 °C.« less
  • Reduced activation ferritic/martensitic steels (RAFs) are leading candidates for blanket and first wall of fusion reactors where effects of displacement damage and helium production are important subjects to be investigated. To obtain systematic and accurate information of microstructural response under fusion environment, dual-ion irradiation method was applied. In order to estimate the microstructural response under fusion neutron irradiation environment, ion-beam irradiation was carried out with helium and metallic self ions. The study is focused on JLF-1 single- and dial-ion irradiated up to 60 dpa at 693, 743 and 793 K. The damage rate and helium injection rate were 1.0 xmore » 10{sup -3} dpa/sec and 15 x 10{sup -3} appm He/sec. At 743 K, void cavity structure was observed under dual-ion irradiation where the contribution of void structure on hardening was not so significant. Irradiation hardening and swelling were depended for the case of dual-ion irradiation. It is attempted to quantitatively relate the dislocation and cavities to the irradiation induced hardening.« less
  • Significant progress has been achieved in the international research effort on reduced activation ferritic/martensitic steels for fusion structural applications. Because this class of steels is the leading structural material for test blankets in ITER and future fusion power systems, the range of ongoing research activities is extremely broad. Since it is not possible to discuss all relevant work in this brief review, the objective of this paper is to highlight significant issues that have received recent attention. These include 1) efforts to measure and understand radiation-induced hardening and embrittlement at temperatures ≤ 400 °C, 2) experiments and modeling to characterizemore » the effects of He on microstructural evolution and mechanical properties, 3) exploration of approaches for increasing the high-temperature (> 550 °C) creep resistance by introduction of a high-density of nanometer scale dispersoids or precipitates in the microstructure, 4) progress toward structural design criteria to account for loading conditions involving both creep and fatigue, and 5) development of nondestructive examination methods for flaw detection and evaluation.« less
  • The status and key issues of reduced activation ferritic/martensitic (RAFM) steels R&D are reviewed as the primary candidate structural material for fusion energy demonstration reactor blankets. This includes manufacturing technology, the as-fabricated and irradiates material database and joining technologies. The review indicated that the manufacturing technology, joining technology and database accumulation including irradiation data are ready for initial design activity, and also identifies various issues that remain to be solved for engineering design activity and qualification of the material for international fusion material irradiation facility (IFMIF) irradiation experiments that will validate the data base.