Grain refinement of T91 alloy by equal channel angular pressing

The effects of grain refinement on the corrosion behavior of three ferritic-martensitic (F/M) steels, HT9, T91, and NF616, and two binary model alloys Fe-15%Cr and Fe-18%Cr in supercritical water (SCW) have been investigated. Grain refinement down to a size of about one micron in the surface regions, was achieved by introducing severe plastic deformation by shot peening. After exposure to SCW with 25 ppb oxygen at 500 8C for up to 3000 h, an improvement in corrosion resistance was observed in grain-refined samples because of the enhanced diffusion of chromium on the surface, through a high density of grain boundaries. The chromium content in the steels and the exposure durations in SCW were determined to be important factors influencing the efficacy of the grain refinement effects. These results are supported by both experimental evidence and theoretical predictions. Another approach for grain refinement, equal channel angular pressing (ECAP), was also investigated for T91 steel. ECAP resulted in lower weight gain due to corrosion compared to the untreated samples, but exhibited a slightly higher weight gain compared to the shot-peened samples after long-term exposures in SCW which is probably caused by different fractions of high-angle grain boundaries in grain-refined regions, introduced by different grain refinement techniques.

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“…ECAPed T91 coupons were received from Texas A&M University and details of fabrication process are described in ref. [20].…”

Section: Methodsmentioning

confidence: 99%

Effect of grain refinement on corrosion of ferritic–martensitic steels in supercritical water environment

Ren

Sridharan

Allen

2010

Materials & Corrosion

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“…3 illustrates the transmission electron microscopy (TEM) micrographs of the initial and ECAPed samples after annealing. According to results reported by Foley et al [35] , the microstructure can be highly refined at high strain rate and reduced processing temperature. Annealing treatment is essential to improve the ductility, and at this stage, dislocation recovery, recrystallization and grain growth will be promoted.…”

Section: Grain Controlmentioning

confidence: 88%

“…Equal channel angular extrusion/ pressing (ECAE/ECAP), a type of SPD, involves pressing a metal billet through a die containing two channels with equal crosssection [32e34] . Foley et al [35] investigated the effect of ECAP on the grain refinement of the modified 9Cre1Mo martensitic steel (T91, "T" stands for "tube"). It was found that the average grain size can be refined over an order of magnitude down to 300 nm, yet the refined grains will grow further with increasing annealing temperature.…”

Section: Grain Controlmentioning

confidence: 99%

Phase Transformation Behavior and Microstructural Control of High-Cr Martensitic/Ferritic Heat-resistant Steels for Power and Nuclear Plants: A Review

Zhou

Liu

et al. 2015

Journal of Materials Science & Technology

150

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“…Additionally, it is also a potential candidate for structural steel in nuclear reactors because of its outstanding irradiation resistance [5][6][7]. So far, it has been widely used as a research benchmark for developing new ferritic heat-resistant steel used for power plants in Japan, Europe, and USA [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Research on splitting phenomenon of isochronal martensitic transformation in T91 ferritic steel

Liu

Zhang

et al. 2012

Phase Transitions

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T91 steel is a representative type of ferritic heat-resistant steel currently used in power plant components, and is a potential candidate for structural steel in nuclear reactors. The isochronal martensitic transformation behaviors during continuous cooling after austenitization in T91 ferritic steel were systematically investigated by high-resolution dilatometry and microstructure observation. The splitting phenomenon of martensitic transformation is accompanied with the precipitation of needle-like M 3 C particles, which is suppressed by rapid cooling after austenitization. The appearance of this splitting is ascribed to the concentration gradient caused by the consumption of alloy element in process of the formation of M 3 C. This concentration gradient results in the appearance of wide martensitic laths ahead of the generation of normally narrow laths. These two types of martensitic laths possess different M s (martensitic start transformation) temperatures, which are attributed to the splitting transformation phenomenon.

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Grain refinement of T91 alloy by equal channel angular pressing

Cited by 33 publications

References 11 publications

Effect of grain refinement on corrosion of ferritic–martensitic steels in supercritical water environment

Effect of grain refinement on corrosion of ferritic–martensitic steels in supercritical water environment

Phase Transformation Behavior and Microstructural Control of High-Cr Martensitic/Ferritic Heat-resistant Steels for Power and Nuclear Plants: A Review

Research on splitting phenomenon of isochronal martensitic transformation in T91 ferritic steel

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