Stress Corrosion Cracking Behavior of Thermally Aged 316L SS in Simulated Oxygenated/Hydrogenated High Temperature and Pressure Water in Nuclear Power Plants
The crack growth rate(CGR)of stress corrosion cracking(SCC)of thermally aged 316L stainless steel(SS)for 2000 h in simulated primary high temperature and high pressure water of 1.5×10-3 B and 2.3×10-6 Li at 320℃and 13 MPa is tested using direct current potential drop(DCPD)system and high temperature and high pressure corrosion test system.Results show the CGR of thermally aged 316L SS is decreased gradually with the dissolved oxygen(DO)content in the solution decreasing from 2×10-6 to 10-6,5×10-7,10-7 and 5×10-9.When the DO content decreasing from 5×10-7 to the lower,the CGR of SCC is decreased significantly.The CGR is further decreased,when the solution is changed from DO to dissolved hydrogen(DH).Scanning electron microscopy(SEM)and electron back scattering diffraction(EBSD)are used to observe the fractures and crack propagation paths of the tested specimens.SCC fracture mainly presents a typical characteristic of intergranular stress corrosion cracking(IGSCC).The change of DO/DH mainly affects the mass transfer process of cracks tip and the repassivation process of the bare surface at cracks tip,which further affects the CGR.The thermal aging of 316L SS for 2000 h has a small effect on its microstructure and CGR of SCC in high temperature and high pressure water.
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