Effect of surface nanocrystallization on stress corrosion cracking behaviors of X80 pipeline steel

Surface nanocrystallization of X80 pipeline steel was realized by ultrasonic surface rolling processing (USRP),and the microstructure of the steel surface was analyzed with optical microscope and transmission electron microscopy. The effects of USRP on the stress corrosion behavior of X80 pipeline steel in NS4 solution was investigated through the slow strain rate tensile tests (SSRT) and scanning electron microscopy. The results show that the USRP refined the grains in the X80 pipeline steel surface to nanometer level. With the negative shift of applied potential,the fracture time,section shrinkage and strain of the X80 pipeline steel significantly decreased,which suggested that the susceptibility to stress corrosion cracking (SCC) increased, and the fractured surface revealed transgranular with the feature of quasi-cleavage. Surface nanocrystallization could extend the fracture time and enhance the stress corrosion resistance of X80 pipeline steel.