Electrochemical Characterization on the Potential Dependent Stress Corrosion Cracking Mechanism of 10Ni8CrMoV High Strength Steel

Abstract

Stress corrosion cracking (SCC) of 10Ni8CrMoV high strength steel influenced by applied potentials in simulated seawater are investigated by combining slow strain rate tensile (SSRT) tests with electrochemical measurements. The potential region corresponding to different cracking mechanism is divided, and the SCC susceptibility is also discussed. The results show that the potential dependent SCC mechanism can be given theoretically by using potentiodynamic polarization at different scanning rate, cyclic voltammetry and dynamic electrochemical impedance spectroscopy (DEIS) measurements, which includes ductile fracture through slip separation with serious uniform corrosion, transgranular SCC (TGSCC) under anodic dissolution (AD), retarded crack growth under the cathodic protection, and intergranular SCC (IGSCC) under hydrogen embrittlement (HE). With the negative shift of the potential, the SCC susceptibility of the steel increases firstly above the open circuit potential (OCP) and decreases later under the cathodic protection, then increases again below the hydrogen evolution potential. The bainite lath grain boundary of 10Ni8CrMoV steel has opposite effects on TGSCC and IGSCC.