Effect of boron on creep deformation behavior and microstructure evolution in 9% Cr steel at 650°C

The effect of boron on creep deformation behavior and microstructure evolution during creep has been investigated for a tempered martensitic 9Cr-3W-3Co-VNb steel containing boron up to 140 ppm at 650°C (923 K) with the emphasis on long term behavior. Creep tests were carried out at 650°C for up to about 70 000 h. The base steel without boron exhibits degradation in creep rupture strength after times above about 1000 h. The addition of boron...