Stress Corrosion Cracking of 23Co14Ni12Cr3Mo Ultra-High Strength Steel in 3.5% NaCl Solution under Constant Load Condition

摘要

The electrochemical responses including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PP) and electrochemical noise (EN) in tress corrosion cracking (SCC) of 23Co14Ni12Cr3Mo ultra-high strength steel were investigated by using constant load (CL) tests. The fracture morphologies were characterized by scanning electron microscopy (SEM). The results showed that under the constant load, the SCC happens, and the reaction resistance of the sample decreases from 9602Ωcm2 to 34.59Ωcm2 with the time increases from 0h to 72h. And as the experiment time increases from 0h to 72h, the self-corrosion potential decreases from -0.426V to -0.626V, while the self-corrosion current increases from 7.02×10-6 A/cm2 to 4.384×10-5 A/cm2 , which shows that as the reaction develops, the corrosion resistance of the sample decreases. Combined the EN response with fracture morphology, the SCC can be divided into three periods: The initial stage of corrosion initiation and development, the middle stage of stress corrosion expansion and the later transient period.