High Temperature Oxidation Behavior of Grain-Refined Inconel 617 for VHTRs

Abstract

Inconel 617 alloy was investigated by exposure at 950°C for 1000 h in air atmosphere. The grain-refined Inconel 617 was obtained by recrystallization after cold rolling of 50%. The grain size was refined from 71μm to 5.2μm. The as-received and grain-refined alloys were oxidized with forming external oxide layer as Cr2O3 and with forming internal oxide as Al2O32O3 along the grain boundary. The formation of Cr2O3 caused the Cr-depleted zone below the external oxide scale. The Cr-depleted zone of grain-refined alloy was thicker than that of the as-received one, while the depth of internal oxide of grain-refined one was shallower. By prolonging the exposure time, the area of internal oxide of grain-refined alloy was gradually decreased. However, as-received one was constantly increased. The internal oxide at the grain-refined alloy had a more homogeneous microstructure.