.40 Cr Steel Stress Corrosion Electrochemical Measurements

SSRT is used for the stress corrosion cracking detection of the 40Cr steel , The fracture behaviours of 40Cr steel in glycerin and seawater and acidic seawater was studied based on the SSRT .With the analysis of the strain-sress curve and sensitivity parameter and scanning electron microscopy (SEM),it was demonstrated that there was distinct sensitivity of 40Cr steel to SCC in acidic seawater ,While no clear tendency to SCC in seawater. By the comparation of the strain-sress curve and sensitivity parameter in different stress rate ,it was confirmed that the right rate is 1.4×10-6 s-1. Meanwhile the fracture character by different polarization potential indicate that the rupture of 40Cr steel acidic seawater was caused by HE.EIS measurements has been used for the detection of scc of 40Cr,EIS measurements wear performed simultaneously on two samples:one stressed with a SSRT and one free of stress ,The time of the crack appearance develoment and rupture of 40Cr steel in acide seawater has been confirmed by the analysis of EIS,It was proved that Bosch model not only been used in passivation system but also used in HE SCC system,it was ascertain in this system the discinplination of the crack of SCC follows the"PDG"theory.It is conside that by the corrosion holl replace the prefabricate of crack.by the comparation of the different passivation system,sodium bicarbonate is choosed as the passivate reagent conside the benefit of the economy and environment,different examination condition showed that throw cathode polarization at this basement, the development of the crack can be controled, the chlorin ion can reduce the electric potential of 40Cr steel.40Cr steel and 35CrMnSi steel are all fabric alloy,they are both used as bolt,by the SSRT,the SCC sensitivity of the 40Cr steel and 35CrMnSi steel is compared,it showed that though as the same material , 35CrMnSi steel through different heat treatment,there is difference in their SCC sensitivity,A51 steel can occur SCC easily,while D44steel has no SCC sensitivity in seawater.although 40Cr steel and 35CrMnSi steel are both used as bolt material, 40Cr steel has no SCC sensitivity in seawater but 35CrMnSi steel(A51 steel) has obvious SCC sensitivity in seawater. fracrure demonstrate that 35CrMnSi steel take on the character of brittleness in seawater.