Effect of Steam Temperature on Oxidation Behavior of GH2984 Alloy as a Candidate for 700℃ Advanced Ultra-supercritical Boilers

Abstract

The oxidation behavior of GH2984 alloy in pure steam at 750℃ and 850℃ was investigated by using X-ray diffractometer (XRD) and scanning electron microscope equipped with energy dispersive spectra (SEM/EDS). Results show that GH2984 alloy is oxidized parabolically with time. The temperature rising greatly promotes the external and internal oxidation and also the evaporation of Cr. The composition and microstructure of the oxide films change obviously. At 750℃, a compact and single-layered (Cr,Mn)2O3 film is formed on alloy surface; the number of voids in oxide scale increases at 850℃, whereas a three-layered oxide scale consisting of thin Fe2TiO5 outer layer and much thicker (Cr,Mn)2O3 middle layer and thinner (Nb,Mo)2O5 inner layer is formed at the elevated temperature. Ti and Al are internally oxidized preferentially along grain boundaries to be TiO2 and Al2O3, respectively; both the number and the size of the two internal oxides increase with the temperature rising.

Keywords

• GH2984 superalloy
• advanced ultra-supercritical coal-fired power plant
• steam
• high temperature oxidation