DEVELOPMENT AND CHARACTERIZATION OF Fe-RASED ODS SUPER ALLOY FOR HIGH TEMPERATURE APPLICATIONS

Abstract

Iron based chromium-aluminum alloys strengthened through `rare earth' oxide dispersoids, usually Y203, are know as ODS alloys. 'Oxide dispersion strengthened (ODS) alloys prepared by versatile alloy design tool namely mechanical. alloying and subsequent consolidation are of interest for =potential application in components for use in power generation and furnace applications. Ferritic steels with oxide dispersion strengthening (ODS), usually Y203, represent an important alloy group for high temperature applications. They offer the potential for high temperature strength and creep resistance by virtue of their dispersion strengthening and form- a stable, compact scale providing excellent high temperature oxidation resistance. This is combined with the use of cost-effective iron as the main alloy constituent. The state of the. art technology on high temperature materials revealed that a considerable scope .existed in developing ODS alloys provided low cost raw materials and processing tools could be utilized. The high point of the investigation has been the development of technology for designing and developing suitable Fe-based ODS alloys using the P/M route. The special attributes have been the utilization of low cost ordinary quality raw materials available from indigenous sources and by. utilizing the P/M forging route rather than extrusion. The aim of the present work is to develop ferritic ODS alloy economically with the properties in comparison to MA 956 alloy through powder forging technique and by taking commercially available metal/alloy powders not bothering about oxygen levels. One of the important objectives of the present investigation is to estimate the influence of deformation and porosity on the final product properties namely its oxidation and hot corrosion resistance. Fe-based ODS alloy was developed with the chemistry of Fe-20% Cr-5.5% Al-0.7% Y203, by taking indigenous raw materials, through mechanical alloying, powder- forging, homogenization treatment and finally rolling. The developed alloy is not a full dense alloy. This alloy was subjected to high temperature cyclic oxidation testing (each cycle of 20 hrs heating and 10 min cooling) at 1.100°C in air and cyclic hot corrosion testing at 900°C(each cycle of 5 hrs heating and 20 min cooling) in Na2SO4-60% V205 environment and microstructural studies and hardness measurements.