Characterization of High Temperature Creep Properties in Recrystallized 12Cr-ODS Ferritic Steel Claddings.

Abstract

The high temperature strengthening mechanism of previously manufactured 12Cr-ODS ferritic steel claddings was clarified. In the recrystallized 12Cr-2W-0.3Ti-0.24Y 2 O 3-ODS ferritic steel cladding, αY 2 TiO 5 type complex oxide formation was responsible for the drastic reduction of oxide particle size and the resulting shortened distance between particles, which led to superior internal creep rupture strength at 973 K because of the high resistance to gliding dislocation. Internal creep deformation was considered to be controlled by the grain boundary sliding associated with grain morphology: the near 11, 9 and 19 coincidence boundaries with a 110 common axis.

Development of 9Cr-ODS Martensitic Steel Claddings for Fuel Pins by means of Ferrite to Austenite Phase Transformation

“…The grain boundary sliding could be possibly dominant deformation mechanism on the analogy with the accelerated creep deformation in 12Cr-ODS ferritic steel claddings. 10) The foregoing findings substantiate the superior high temperature creep rupture strength of 9Cr-ODS martensitic steel claddings, with possibility indicated of potential to be further improved in their creep strength. Making a coarser grain formation would be unique solution to approach the dispersion strength level on the basis of above findings that the accelerated deformation could be arisen from grain-boundary sliding among extremely fine and homogeneous grains of less than 1 µm in martensitic 9Cr-ODS cladding.…”

“…This interaction corresponds to the threshold stress for deformation that was proposed by Srolovitz. 15) The following threshold stress σ v can be estimated according to the equation presented in the paper: 10) Fig. 16 Histogram of oxide particles diameter distribution in M91, M92 and M93 measured by image analysis of transmission electron micrographs…”

“…6) In the ODS ferritic steels with a basic composition of FeCr-W-Ti-Y 2 O 3 , grain morphology control by recrystallization has been shown to be indispensable not only for softening the material hardened in the process of cold-rolling but also suppressing the strength degradation by grain boundary sliding. [7][8][9][10] As an another approach, phase transformation from ferrite-martensite (α) to austenite (γ ) was demonstrated to be capable method for controlling the grain morphology by using the extruded bars of ODS martensitic steels. 11) In this study, by applying α-γ phase transformation in the ODS martensitic steels, cladding production test is executed using the cold-rolling process at room temperature.…”

Microstructural changes upon annealing in ODS-strengthened ultrafine grained ferritic steel

“…This observation can be explained by the interactions of the grain boundaries in ferritic matrix with the nanoparticles present in the material [19]. Especially, Y-Ti-O nanoparticles are expected to suppress grain growth imparting a very good thermal stability of the ODS ferritic steels [11,12].…”

Oxide Dispersion Strengthened Steels for Advanced Blanket Systems

“…Oxide dispersion strengthened (ODS) steels have been developed for application to fuel claddings of fast reactors [18][19][20][21][22][23][24][25] where high performance materials properties are required to meet the severer conditions of in-core environment such as high doses of neutron irradiation at high temperatures. The ODS steel consists of a number of nanoscaled fine oxide particles in the matrix of the RAFM steel, and resultantly, the trapping sites for radiation defects increase with the number of the particles in comparison to the RAFM steel since the oxide particles/matrix (P/M) interfaces also play a role of trapping defects induced by irradiations [26].…”