Development of Oxide Dispersion Strengthened Steels for FBR Core Application, (II) Morphology Improvement by Martensite Transformation.

Abstract

Previously manufactured oxide dispersion strengthened (ODS) ferritic steel cladding tubes had inferior internal creep rupture strength in the circumferential hoop direction. This unexpected feature of ODS cladding tubes was substantially ascribed to the needle-like grain structure aligned with the forming direction. In this study, the grain morphology was controlled by using the martensite transformation in ODS martensitic steels to produce an equi-axial grain structure. A major improvement in the strength anisotropy was successfully achieved. The most effective yttria addition was about lmass% in improving the strength of the ODS martensitic steels. A simple addition of titanium was particularly effective in increasing the strength level of the ODS martensitic steels to that of ODS ferritic steels.

Feasibility Study of Supercritical Light Water Cooled Reactors for Electric Power Production, Progress Report for Work Through September 2003, 2nd Annual/8th Quarterly Report

“…The reference fuel-cladding material is an Oxide Dispersion Strengthened (ODS) ferritic steel, designated Incoloy MA956. ODS ferritic alloys have been shown to possess excellent mechanical, corrosion and irradiation properties [Harper 2002, Bottcher et al 2002, Ukai et al 1998]. Alloy MA956 in particular is commercially available in the U.S. [Special Metals 2003], and its properties are well known [Klopp 1992].…”

Production and Properties of Nano-scale Oxide Dispersion Strengthened (ODS) 9Cr Martensitic Steel Claddings

“…The chemical composition of the material for fuel cladding application to fast reactors was proposed to be Fe-0.13C-9Cr-2W-0.2Ti-0.35Y 2 O 3 , and substantially elongated grains formed by cold-rolling were made into equi-axied grains by means of a to g phase transformation. 8,9) In this study, claddings with a standard composition of Fe-0.13C-9Cr-2W-0.2Ti-0.35Y 2 O 3 are developed using the cold-rolling process, and the high temperature mechanical properties of the produced claddings are investigated.…”

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

“…[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. The high temperature mechanical properties of claddings produced are investigated, focusing on varying titanium and yttrium oxide (Y 2 O 3 ) contents that could significantly affect their mechanical properties.…”