Effect of Chromium, Aluminum and Nickel on Microstructure and Reverse-S Type Creep Rupture Strength of High Cr Ferritic Heat Resistant Steels

Microstructure and creep strength of two high-Cr ferritic heat resistant steels –11Cr and 9Cr - were investigated at a temperature of 650°C. 11Cr steel containing relatively higher carbon, aluminum and nickel than 9Cr steel showed a significant drop in creep strength after 1000 h, while 9Cr showed a recovery in creep strength after a slight drop. 11Cr steel contained M23(CB)6, Z phase and a relatively coarsened Laves phase as precipitates after...