Corrosion Behavior of Nickel Base Alloy 800H in High-temperature and High-pressured Water

Susceptibility to stress corrosion cracking(SCC) of nickel based alloy 800H was studied in supercritical water at 550 ℃, 25 MPa, 600 ℃, 25 MPa and 650 ℃, 25 MPa respectively, and its general corrosion behavior in supercritical water at 650 ℃, 25 MPa and in subcritical water at 290 ℃, 15.2 MPa respectively as well. The mechanical properties of alloy 800H were also examined at different temperatures in air. The strain-stress curve of slow strain rate tensile(SSRT) tests shows that the strength of alloy 800H decreases as temperature increases. The ex situ scanning electron microscopy(SEM) observation shows that alloy 800H under the three conditions in supercritical water all exhibits susceptibility to SCC. The SSRT tests in air show that the yield strength and tensile strength of alloy 800H decrease as temperature rises. The results of general corrosion experiment in supercritical waters show that the weight gain of the alloy follows a parabolic law; however, in subcritical water the alloy exhibits mass loss.