Alloy Design of Creep- and Oxidation-Resistant 9%Cr Steel for High Efficiency USC Power Plant
|Periodical||Materials Science Forum (Volumes 706 - 709)|
|Main Theme||THERMEC 2011|
|Edited by||T. Chandra, M. Ionescu and D. Mantovani|
|Citation||Fujio Abe, 2012, Materials Science Forum, 706-709, 3|
|Online since||January, 2012|
|Keywords||Boiler, Coal Fired Power Plant, Creep Strength, Ferritic Steel, Oxidation, Welded Joint|
Ferritic heat resistant steels are strongly desired to expand their maximum use temperature up to 650oC for application to the next highest temperature components of highly efficient, low emission ultra-supercritical (USC) power plant with maximum steam temperature of 700 oC. This minimizes the requirement of expensive nickel base superalloys. Critical issues for the development of ferritic steels for 650 oC USC boilers are the improvement of oxidation resistance as well as long-term creep rupture strength, including welded joints. The optimized combination of boron addition and dispersion of nanometer-sized vanadium nitrides significantly improves long-term creep strength of 9% Cr steel and also exhibits no degradation in welded joints at 650 oC. The protective Cr2O3-rich scale forms on the surface of 9% Cr steel by pre-oxidation treatment in Ar gas, which significantly improves the oxidation resistance in steam at 650oC.