Long-Term Service Experience With Advanced Austenitic Alloys in Eddystone Power Station

Abstract

A service exposure test of advanced austenitic alloys was performed at Eddystone Power Station Unit 1. The alloys tested were TP347HFG, SUPER304H and HR3C as well as 17-14CuMo as a reference material. They were installed in the final super-heater section in 1991 and were removed in 2004. The service exposure duration is 75,075 h with the steam temperature and pressure estimated 615 °C and 35 MPa, respectively. Post exposure examination has proved no marked hot-corrosion and steam oxidation have occurred for the TP347HFG, SUPER304H and HR3C specimens, while severe hot-corrosion and exfoliation of steam-oxide films was pronounced in 17-14CuMo specimens. It is also found that HR3C exhibits the highest tensile strength with a lowest ductility and TP347HFG does vice versa, while the strength of SUPER304H is equivalent to that of 17-14CuMo with much better ductility. Short-term creep rupture strengths of these alloys have been reduced to some extent after the long-term service exposure and a longer-term creep rupture testing has been in progress. Microstructural evolution of the TP347HFG, SUPER304H and HR3C as well as 17-14CuMo during the long-term service exposure have been analyzed using a detailed TEM examination and the chemical analysis of extraction residue of the exposed specimens.