Multi-Phase High Temperature Alloys: Exploration of Alumina-Forming, Creep-Resistant Austenitic Stainless Steels

摘要

Work in 2007 focused on the development of a new class of heat-resistant austenitic stainless steel alloys which achieved a unique combination of high-temperature creep strength and excellent oxidation resistance via protective Al(sub 2)O(sub 3) scale formation. Strengthening is achieved via the formation of stable nano NbC carbides with/without Fe(sub 2)Nb and related intermetallic phase dispersions, with controlled levels of Al to enable Al(sub 2)O(sub 3) scale formation in both air and air + water vapor environments up to (approx)800-900 C. The developed alloys exhibit comparable creep resistance to that of the best commercial heat-resistant austenitic stainless steels, and the protective Al(sub 2)O(sub 3) scale formation provides oxidation resistance superior to that of advanced Cr(sub 2)O(sub 3)-forming heat-resistant austenitic alloys. Preliminary screening also indicated that the developed Al-modified alloys were amenable to welding.