Oxidation Behavior of UHP Fe-Based Model Alloy and SUS310S Steel in Superheated Steam and Supercritical Water Conditions

Abstract

The quest for improvements in cycle efficiency of energy production plants leads to progressively higher operating temperatures and pressures in steam boiler. For this reason, the oxidation resistance of structural materials is the key issue, and hence, the consequences of increased growth rate of the oxides pose serious concern, such as oxide exfoliation. The oxidation behavior of ultra-high-purity (UHP) Fe–23Cr–23Ni–2Mo–0.6Nb wt% model alloy and SUS310S in steam and super critical water at atmospheric pressure and 25 MPa, respectively, and at 973 K (700 °C) is investigated. To elucidate the oxidation behavior, weigh gain measurement and characterization of the resulting oxide were performed. The critical chromium content to form and maintain protective oxide increased with increasing the pressure, 23 wt% in steam and 26 wt% in SCW conditions. Grain refinement was efficient for enhancing the oxidation resistance of SUS310S.