Time-lapse observation of crevice corrosion in grade 2205 duplex stainless steel

Aoki, So; Engelberg, D. L.*

Materials, 16(15), p.5300_1 - 5300_13, 2023/08

https://doi.org/10.3390/ma16155300

The objective of this study was to investigate and visualize the initiation and propagation behaviour of crevice corrosion in grade 2205 duplex stainless steel by means of time-lapse, in-situ observations. All observed crevice corrosion initiated close to the edge of the washer, where the crevice gap was very tight. Crevice corrosion then expanded underneath the crevice forming disk into areas with wider gaps towards the crevice mouth. This was associated with a rise in anodic current, leading into hydrogen gas evolution within the crevice. Once crevice corrosion reached the crevice mouth, the corrosion propagated Circumferentially, but also in depth.

Relationship between the microstructure and local corrosion properties of weld metal in austenitic stainless steels

Tokita, Shun*; Kadoi, Kota*; Aoki, So; Inoue, Hiroshige*

Corrosion Science, 175, p.108867_1 - 108867_8, 2020/10

https://doi.org/10.1016/j.corsci.2020.108867

The purpose of this study is to evaluate the corrosion resistance of weld metal by electrochemical methods and discuss the relationship between microstructure and corrosion resistance. Intergranular and pitting corrosion resistances were measured using electrochemical potentiokinetic reactivation (EPR) test and pitting potential measurement respectively. The reactivation ratio and pitting potential corresponded to its chemical composition. The specimens containing more Cr and Mo showed higher resistance. In the EPR test, the dendrite core with a relatively low Cr content was corroded. In the pitting corrosion test, Nb carbide became the initiation site of pitting corrosion which propagated along the cell structure.

Gas-flow humidity control system for neutron reflectivity measurements

Arima-Osonoi, Hiroshi*; Miyata, Noboru*; Yoshida, Tessei*; Kasai, Satoshi*; Ouchi, Keiichi*; Zhang, S.*; Miyazaki, Tsukasa*; Aoki, Hiroyuki

Review of Scientific Instruments, 91(10), p.104103_1 - 104103_7, 2020/10

https://doi.org/10.1063/5.0021128

Ion irradiation effects on FeCrAl-ODS ferritic steel

Kondo, Keietsu; Aoki, So; Yamashita, Shinichiro; Ukai, Shigeharu*; Sakamoto, Kan*; Hirai, Mutsumi*; Kimura, Akihiko*

Nuclear Materials and Energy (Internet), 15, p.13 - 16, 2018/05

https://doi.org/10.1016/j.nme.2018.05.022

Radiation hardening and microstructural evolution of ion irradiated 12Cr-6Al ODS ferritic steel was studied. Ion irradiation experiments were performed using Fe ions up to the nominal displacement damage of 20 dpa at the irradiation temperature was 300C. The monotonical increase of radiation hardening with dose was confirmed by experimentally obtained hardness data. The radiation hardening was also calculated theoretically by introducing the microstructural character examined by TEM into the dispersed barrier hardening model. The results showed a good agreement with the experimentally obtained data up to 5 dpa, while a slight discrepancy was found between theoretical and experimental hardness values at 20 dpa. Radiation hardening was mainly caused by irradiation-induced defect clusters below the irradiation dose of 5 dpa. As the irradiation dose increased toward 20 dpa, an additional influence of the radiation appeared, which was assumed to be induced by ' phase transformation.

New precise measurement of muonium hyperfine structure interval at J-PARC

Ueno, Yasuhiro*; Aoki, Masaharu*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; Ito, Takashi; Iwasaki, Masahiko*; et al.

Hyperfine Interactions, 238(1), p.14_1 - 14_6, 2017/11

https://doi.org/10.1007/s10751-016-1381-7

Preferential dissolution mechanism of or phase in crevice corrosion of duplex stainless steels

Aoki, So

Zairyo To Kankyo, 65(2), p.45 - 50, 2016/02

https://doi.org/10.3323/jcorr.65.45

Duplex stainless steels (DSS) possess a ferritic phase matrix dispersed with austenitic phase precipitates. Due to the chemical compositional arrangement and the characteristic ferritic/austenitic dual phase structure, DSS possess superior mechanical properties and corrosion resistance without sacrificing economic performance. In any case, even DSS suffer from crevice corrosion. Accordingly, the measure of crevice corrosion is of pragmatic importance. The modes of crevice corrosion on DSS were complex because of its preferential dissolution and distinguishable as some types from the outside to the center of the crevice: the passivity retention region, the region with preferential dissolutions of austenitic phase precipitates, and the region with preferential dissolution of the ferritic phase matrix. It is described the study to elucidate the preferential dissolution mechanism of crevice corrosion on DSS, based on the in-situ observation of crevice corrosion dissolution behavior, and the analysis of dissolution behavior of DSS, ferritic and austenitic phases in a simulated crevice solution.

Dissolution behavior of duplex stainless steels in crevice corrosion growth step

Aoki, So; Nada, Yushi*; Sakai, Junichi*

Zairyo To Kankyo, 64(8), p.366 - 372, 2015/08

https://doi.org/10.3323/jcorr.64.366

The objective of this study is to clarify dissolution behavior of duplex stainless steels in crevice corrosion growth step. Crevice corrosion grew on the duplex stainless steels by holding potential at various values. After a certain period, dissolution behavior of the crevice corrosion was analyzed based on observation of corroded area. Change in crevice corrosion dissolution behavior with time was also investigated by means of in-situ observation. Four types of dissolution regions could be observed in the corrosion area from outside toward inside direction, i.e. tip of the corroded area toward initiation point, in a crevice; they were passive region, the preferential dissolution region of austenitic phase, both phase dissolution region, and the preferential dissolution region of ferritic phase. The crevice corrosion which maintained that four dissolution regions grew toward the edge of the crevice. This dissolution behavior was given at all the potential where crevice corrosion occurred. The result is described by the micro galvanic cell between inside and outside the crevice consists of IR drop.

Identified charged hadron production in collisions at = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

https://doi.org/10.1103/PhysRevC.83.064903

Transverse momentum distributions and yields for , and in collisions at = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different collisions. We also present the scaling properties such as and scaling and discuss the mechanism of the particle production in collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.

None

*; *; *; *; ; ; Yabuuchi, Satoshi

PNC TY7651 95-001, 59 Pages, 1995/04

PNC-TY7651-95-001.pdf:4.24MB

None

Hydrogen-methanol production system using nuclear process heat

; Omoto, Akira*; *; *; *; *; *; *; *; *; et al.

Enerugi, Shigen Gakkai Dai-11-Kai Kenkyu Happyokai Koen Rombunshu, p.33 - 38, 1992/00

no abstracts in English