Investigation of nickel-based alloys exposed to supercritical water environments

Experimental tube reactors made of the nickel based alloys C-22 and Inconel 625 were exposed to supercritical water (SCW) environments. During this experiments, various inclusions and precipitates from a submicron size range to bulk scale-like layers were formed. The corrosion products and layers, located at the sub- and supercritical parts of the tubular flow reactors, were imaged and analyzed by field-emission scanning electron microscopy, combined with an energy-dispersive X-ray spectrometer (FESEM/EDX). The microanalysis was performed on metallographically prepared specimen. To obtain additional information regarding surface morphology, scanning force microscopy (SFM) and microhardness testing were applied at selected specimen.