2015

Gong, Mengqiang; Zhou, Zhangjian; Hu, Helong; Penttilä, Sami; Toivonen, Aki

The corrosion behavior and oxide layer structure of two 14Cr ODS (Oxide Dispersion Strenghtened) steels with or without alloying element of Al have been investigated in supercritical water (SCW) at 650℃/25MPa for exposure times of 100h, 300h and 1000h. The oxide structure was studied using scanning electron microscope (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). Both ODS alloys showed a three-layer oxide structure after 1000h of exposure in SCW. The 14Cr-Al samples exhibited a structure with Fe2O3 in the outer layer, a mixture of (Cr, Fe)3O4 and (Al,Cr)2O3 in the inner layer, and a mixture of metal and oxide grains Al2O3 in the diffusion layer. The outer layer of Al-free samples consist of Fe2O3, the inner layer and the diffusion layer contain (Fe, Cr)3O4 and Cr2O3, respectively. Cracks, pores and exfoliations could be observed for both alloys after SCW exposure up to 1000h.