5-9 September 2016
Prague Congress Centre
Europe/Prague timezone

P1.182 Effects of mechanical alloying parameters on microstructure and impact properties of ODS ferritic steels

5 Sep 2016, 14:20
1h 40m
Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Foyer 2A (2nd floor), 3A (3rd floor)

Prague Congress Centre

5. května 65, Prague, Czech Republic
Board: 182
Poster I. Materials Technology P1 Poster session

Speaker

Noriyuki Y. Iwata (National Institute of Technology)

Description

The R&D of high performance fuel cladding materials has been considered to be essential for the realization of fusion and Gen IV fission energy systems. The 9Cr oxide dispersion strengthened (ODS) martensitic steels was developed for applying as cladding materials of sodium-cooled fast breeder reactors (FBRs). The steels exhibited good compatibility with sodium, while the corrosion resistance was not good enough in supercritical pressurized water (SCPW) and lead-bismuth eutectics (LBE). High-Cr ODS ferritic steels added with Al showed a drastic improvement in the corrosion resistance in SCPW and LBE. ODS steels are usually produced by powder metallurgy techniques involving a series of steps: (i) mechanical alloying (MA) of a powder mixture, (ii) canning and degassing of the powder, (iii) consolidation of the powder particles by hot extruding, and (iv) normalizing and tempering heat treatment of the consolidated products. The material performance of ODS steels is controlled by the dispersion morphology of dispersoids that is significantly influenced by the processing conditions not only during heating but also during milling. Four different ODS ferritic steels, Fe-16Cr-(0/4)Al-0.1Ti-0.35Y2O3, in wt%, were prepared by MA of elemental powders with Y2O3 particles either in attritor mill or in planetary ball mill, and consolidated by hot extruding. Milling in air is effective to reduce the particle size of MA powder. SEM and PSD analyses showed that the processing capacity of powder particles during planetary ball milling has improved twofold compared to our previous condition. In this study, recent experimental results on the effects of MA parameters, such as milling atmosphere, device, and Al addition, on the microstructure and Charpy impact properties of the ODS ferritic steels will be shown to conclude that lowering the excess oxygen and nitrogen contents in steels is the critical issue for enhancing their impact properties.

Co-authors

Akihiko Kimura (Institute of Advanced Energy, Kyoto University, Uji, Kyoto, Japan) Noriyuki Y. Iwata (National Institute of Technology, Kurume College, Kurume, Fukuoka, Japan) Ryuta Kasada (Institute of Advanced Energy, Kyoto University, Uji, Kyoto, Japan) Takanari Okuda (Kobelco Research Institute, Inc., Kobe, Japan)

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