Effect of Environment Solution and Hydrogen Charging Time on Stress Corrosion Cracking of 40CrNi2Si2MoVA Steel

Double cantilever (DCB) specimens and constant load tensile stress corrosion tests were used to study the effects of environmental media and hydrogen charging time on the stress corrosion behavior of 40CrNi2Si2MoVA ultra-high strength steel. The results show that the stress corrosion cracks of 40CrNi2Si2MoVA steel DCB samples in different solution media tend to bifurcate at the pre-crack tip. The angles between the cracks and the pre-crack axis direction increase continuously during the growth process, and finally tend to be perpendicular to the pre-cracks. The Cl⁻ ions have a greater impact on stress corrosion of 40CrNi2Si2MoVA than SO₄²⁻ ions, which can accelerate crack initiation and expansion more significantly. With the increase of hydrogen charging time, the fracture time of 40CrNi2Si2MoVA is shortened, the plasticity of the material decreases, and the brittleness increases. Fracture mode gradually changes from ductile fracture to brittle fracture.