Creep behaviour and microstructural evolution for TP347H austenite steel used in China power plants.

TP347H (18Cr-10Ni-Nb) austenite steel has high creep strength and has been used as the material of tubes in 600°C USC power plants in China. The TP347H materials used in actual power plants are useful for estimating the changes of material properties caused by long-term ageing and damage at low stress conditions. An understanding of the long-term microstructural evolution under actual use conditions is a key for the improvement of these heat resistant steels. In this article, microstructural evolution of TP347H steel under different service conditions in power plants was studied using optical microscope (OM), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) techniques. The results show that M23C6, MX and σ phases were found to precipitate. A quantitative characterisation of microstructure evolution was evaluated during long-term exposure, focusing on the content and the size of precipitates in the TP347H steel after long-term service. [ABSTRACT FROM AUTHOR]