ODS STEELS BY POWDER FORGING

Abstract

The development of radiation resistant steels for fusion reactors would rely heavily on the rich experience gained in the commercialization of fast reactor core component materials, in the last three decades. The structural materials for fast breeder reactors are subjected to a very demanding environment of high energy neutron flux coupled with high temperatures. P/M ODS ferritic stainless steels have proven to be an adequate material for fast breeder reactor fuel cladding application. The dispersed fine Y203 oxide particles improve high temperature strength by blocking mobile dislocations and retard irradiation swelling by acting as trapping sites for point defects induced by irradiation. These Oxide dispersion strengthened steels may enable even higher service temperatures up to 923-1073 K in Sodium cooled Fast Reactor applications. Iron based ODS alloys synthesized by mechanical alloying have been mainly consolidated by hot isostatic pressing (HIP) and hot extrusion. HIP is associated with the problem like residual porosity, Prior particle boundaries and Hot extrusion is associated with anisotropy in mechanical properties. Powder forging is a consolidation technique which is used to produce fully dense material. Powder forging involves the deformation of a powder preform in which considerable lateral flow occurs. The lateral flow of forging leads to considerable shear, which breaks up any oxide surfaces on the particles and enhances bonding between particles. This enhances dynamic properties such as fracture toughness and fatigue strength. In the present investigation mechanical alloying of elemental Fe-10%Cr-0.3%Y,03 was carried out.. The present work includes sintering and powder forging of pre-alloyed ferritic stainless steel powder 409L and yttria. Further it includes the effect of amount and particle size of yttria on hardness and microstructure of the alloys.