Hot extrusion of oxide dispersion strengthened (ODS) steels - a technology development

Full text: Fast breeder reactor technology is the back bone of second stage of nuclear power programme in India. These reactors operate at high neutron fluence and high operating temperature. High neutron doses and high operating temperature limits the burn up of oxide fuel due to damages in cladding tube. Future material developments for clad tubes of advanced fast breeder reactors are governed by material attributes such as high void swelling resistance under irradiation condition and higher creep strength. Oxide Dispersion Strengthened (ODS) steel is a prospective choice over conventional austenitic stainless steel such as D9 and ferritic/martenstic steels such as Modified 9 Cr-1 Mo, due to its better creep strength at above 800K operating temperature in reactor. Manufacturing of 9 Cr W-ODS martensitic steel fuel cladding tube has been taken up at Nuclear Fuel Complex, Hyderabad with a combination of hot working and subsequent thermo mechanical processing. Manufacturing technology of ODS steel tube is critical with respect to chemical composition, dimensional tolerances and achievement of mechanical properties. Extrusion process has been developed to produce 24/18 mm q rod to convert it further into tubular shape by cold Pilgering. This paper discusses the two stage hot extrusion to produce near net shape density in rod product along with design of cold pilgering schedule. Optimum extrusion parameters such as temperature, strain rate and lubrication condition are also explained in this developmental work