Long-Exposure Air and Steam Oxidation Characteristics of IN 617 Alloys

Abstract

India’s growing power demands and emission norms require more efficient coal-based power plants. The shifting of power plants from subcritical to ultra-supercritical (USC) steam conditions could improve efficiency by 12% and reduce CO2 emissions by 35%. There is a need to develop and qualify materials under ultra-supercritical steam conditions with high temperatures and high pressures in laboratory scale. The sample materials were exposed to high temperatures of 700 °C under air and high pressure steam at 700 °C/243 bars for 1000 h in as-received and grain-boundary-enhanced conditions. Grain boundary enhancement included optimization of a thermo-mechanical process involving cold rolling and annealing of samples. The effect of air and steam oxidation on IN 617, a nickel-based candidate superalloy, was analysed. Steam oxidation was performed on a custom-built PARR 4650 series autoclave, and the oxidized samples were characterised under scanning electron microscopy, to evaluate the oxide scales. The grain-boundary-engineered material performed better than the as-received samples. IN 617 overall fared better under both air and steam conditions, with far less weight gains.

Keywords

• ultra-supercritical
• IN 617
• grain boundary enhancement
• grain size
• oxide layer
• weight gain