Thermal Degradation Behavior of Inconel 617 Alloy

Abstract

Inconel 617 alloy is a candidate material for potential use as an intermediate heat exchanger (IHX) and as a hot gas duct (HGD) in high-temperature gas-cooled reactors (HTGRs) for H-2 production. This alloy supports severe operating conditions of a pressure over 8 MPa and temperature that exceed 950 degrees C in He gas with some impurities. In this work, the oxidation behavior of Inconel 617 alloy was studied after exposure at 1050 degrees C for 2000 h in both air and He atmospheres. The external oxide scale was mainly composed of Cr2O3 and small amount of TiO2. The internal oxide was observed just below the external oxide scale and was distributed on the grain boundaries. The internal oxide was confirmed as Al2O3. The Cr-depleted zone and internal oxide in both environments became thicker as the exposure time increased. The Cr2O3 in air at 2000 h was thinned in terms of its scale by CrO3 evaporation and delamination. The Cr2O3 in He was constantly maintained.