Stress Corrosion Cracking Of High-strength Steel Research Articles

Mixed-Mode Stress-Corrosion Cracking of High-Strength Steel: the Role of Cyclic Load History

Mixed-Mode Stress-Corrosion Cracking of High-Strength Steel: the Role of Cyclic Load History

Stress corrosion cracking of high-strength steels

The threshold stress intensity of stress corrosion cracking (SCC) in the NaCI solution, K ISCC , has been measured for five low alloy steels. The effects of yield strength, alloy elements, microstructure and grain size on K ISCC were studied. The results showed that K ISCC decreased exponentially with increasing yield strength, σ ys , i.e., K ISCC = 1.38 10 6 exp(-8.26 10 -3 σ ys ) for 40CrMoV steel and K ISCC = 1.42. 10 6 exp(-4.66. 10 -3 σ ys ) for 30CrMnSiNi steel. For low-alloy high-strength steels with σ ys = 1400 MPa, the effect of alloy elements, microstructure and grain diameter larger than 7 μm on K ISCC was little. The threshold stress intensity of hydrogen-induced cracking during dynamical charging for 40CrMoTi steel decreased linearly with the logarithm of the concentration of diffusible hydrogen, C 0 , i.e., K IH = 31.3-9.1InC 0 . This equation was also applicable to SCC of a high-strength steel in aqueous solution, and in this case, C 0 is constant. The critical hydrogen enrichment concentration, C th , necessary for SCC of high-strength steel in water decreased exponentially with the increase in yield strength. It was possible to deduce the relationship between K ISCC and σ ys , i.e., K ISCC = Ak 1 exp(-k 2 σ ys ), where A = 3RT √πρ /2(1 + v) V H , k 1 and k 2 are constants, which depend upon the compositions and microstructure of the steel as well as the test conditions.

Investigation of the Mechanism of Stress Corrosion Cracking in High Strength Steels

Abstract An analysis is given of the modern outlook on the mechanism of cracking in high strength steel in the case of stress corrosion cracking (SCC). It is shown that numerous experimental data cannot be interpreted in terms of hydrogen embrittlement when it is considered as the only mechanism of crack growth. A phenomenon is described of multiple effects of cathodic polarization on the rate of crack growth in cracking of high strength steels. A new mechanism of SCC is suggested, whose main feature is found in that it not only allows for, but is in fact based upon the possibility of SCC of high strength steels by several mechanisms: local anodic dissolution, hydrogen embrittlement, and adsorption strength reduction. The mechanism entails alternation of rate-limiting processes, depending on various metallurgical and electrochemical factors, and on crack growth rate, which affect the kinetics of formation of barrier layers at the crack tip. A definition of critical growth rate is introduced, which is then investigated as function of a number of factors.

Investigation of stress-corrosion cracking of high-strength steels in certain media

Investigation of stress-corrosion cracking of high-strength steels in certain media