Compatibility of Nickel-Based Alloys with Supercritical Water Applications: Aging Effects on Corrosion Resistance and Mechanical Properties

Abstract Corrosion-resistant Ni-based alloys are thought to be strong candidates as a structural material for chemical processes using supercritical water (SCW). In recent years, Cr was considered as the most important alloying element to improve corrosion resistance in SCW. However, high Cr content can cause a phase transformation in Ni-based alloys because of poor phase stability at elevated temperatures for SCW processes from 400°C up to 650°C. The change in the microstructure of the alloy can lead to degradation in corrosion resistance and mechanical properties. In this study, thermal aging effects on corrosion resistance and mechanical properties of various Ni-based alloys were investigated through a corrosion test in SCW containing 0.01 mol/kg sulfuric acid (H2SO4) at 400°C/30 MPa and using Charpy impact tests. A reduction in impact toughness was observed for all the alloys tested, and the reduction in corrosion resistance was more significant for alloys with higher Cr content. The importance of sus...