On precipitates in Fe–Ni base alloys used for USC boilers

Abstract

This paper overviews the effects of some precipitates in Fe–Ni base boilers materials. The volume fraction of these precipitates is usually below 10% for maintaining the microstructure stability and manufacture ability. They appear in a number of morphologies, but all of them improve the creep strength when they exist in small size. For the alloys serviced below 650°C, the strengthening precipitates disperse within the matrix and maintain their diameter below 100 nm during long time exposure. For the alloys serviced above 650°C, the strengthening precipitates are normally larger than 100 nm in equivalent diameter. They may experience long growth duration and thus keep their size below 500 nm. Meanwhile, the precipitates may improve creep strength when they are dispersed over the grain boundaries.

Keywords:

• Boiler materials
• Strengthen phase
• Precipitates
• Grain boundary

Acknowledgements

This research is supported by the National Science Foundation of China (NSFC) grant nos. 51301130 and 51301131.