Air Oxidation Behavior of Sanicro-25 with Different Surface Finishes

Abstract

Sanicro-25 is a high-temperature material used as the structural material for steam superheaters and reheaters in advanced ultra-supercritical power plants. The air oxidation behavior of Sanicro-25 with various surface roughnesses is being assessed at 650 °C for about 1000 h. Different surface-roughened samples were studied, namely polishing the sample up to diamond finish, grinding up to (80-grit finish and 600-grit finish) and grit blasted. The diamond finish sample showed more weight gain than others, and higher weight gain was observed in the initial oxidation stage. Attributed to different surface preparations leads to defects at different levels, which further alters the diffusion of various elements. The diamond finish sample showed the presence of Cr-rich oxides, and other samples showed the presence of Fe-rich oxides. Smooth surfaces promoted the formation of thick protective oxide scales.