Stress corrosion crack of new ultrahigh strength steel

The behavior of stress corrosion crack of two kinds of ultrahigh strength steel, 23Co14Ni12Cr3 and 40CrNi2Si2MoVA, in 3.5% NaCl solution are investigated with the constant load tensile stress corrosion method. The microstructure and fracture surface of the two ultrahigh strength steels are analyzed by metalloscopy and scanning electron microscopy (SEM). The results of constant load tensile stress corrosion test show that at the same stress level the fracture time of steel 23Co14Ni12Cr3 is longer than that of 40CrNi2Si2MoVA, which means 23Co14Ni12Cr3 possesses better corrosion resistance. The fracture morphology analysis shows that the fracture surface of the two ultrahigh strength steels has the characteristic of intergranular fracture and dimple fracture under the joint action of stress and corrosive solution.