Development of Ni-Cr base Alloys for Steam Generator Tubes and other Parts in Pressurized and Boiling Water Reactors

Incoloy-800 is a nickel-chromium alloy that is best known for its ability to maintain a stable structure during prolonged exposure to high temperatures. Incoloy-800 possesses more than the strength to withstand the basic stress caused by heat, though. It has high levels of resistance to oxidation and carbonization, making it one of the most effective materials for use in carbonizing equipment and heating element sheathing. Ni-Cr-Fe alloy that resists high temperature oxidation. This alloy is a first choice for an upgrade from the 300 series stainless steels when improved performance or strength at temperature is required. It is an iron based super alloy for steam generators and its chemical composition is: - Ni=30-35% - Cr=19-23% - S=0.015% - Al=0.15-0.6% - Ti=0.15-0.6% - Cu=0.75% - C=0.1%max. - Si=1% - Mn=1.5% - Fe=balance The chromium in the alloy imparts resistance to oxidation and corrosion. The high percentage of nickel maintains an austenitic structure so that the alloy is ductile. The nickel content also contributes resistance to scaling, general corrosion, and stress-corrosion cracking. The iron content provides resistance to internal oxidation. Our present study aims to find out the manufacturing process of the Incoloy-800. The Incoloy-800 tubes are manufactured in the Nuclear Fuel Complex, by the extrusion process. Initially the powders of the alloy are mixed to proper composition and then compacted at high pressure. The compacted components are heated in the Electric Arc Furnace to prepare the Billets. The Billets are extruded to form tubes and then it undergoes pillgaring to decrease the thickness of the tube wall and increase the length. The samples are taken from the billet, from the tube after extrusion and from the tube after final pillgaring. From the obtained samples the properties of the Incoloy-800 alloy is analyzed before extrusion, after extrusion and after final pillgaring. In the microstructure of the incoly-800 becomes finer as it undergoes pillgaring and mechanical properties of the Incoloy-800 alloy changes with microstructure.