Hydrogen Induced Stress Corrosion Cracking of Austenitic Stainless Steel Alloyed by Nitrogen

摘要

An investigation has been performed into the effect of alloyed nitrogen in austenitic stainless steel on hydrogen-assisted stress-corrosion cracking. The effect of hydrogen was determined by the cathodic polarization of test specimens, which were loaded to different percentages of R_(p0,2), as well as by the recording of hydrogen elongation curves. On the basis of the observed events on the electrode surfaces in the case of the mutual action of stress corrosion and hydrogen, it was found that NH_4~+ ions were formed on the interface between the passive film and the electrolyte, in which case the H~+ ions from the corrosive medium are used up. This is one of the main reasons for the increased resistance of nitrogen-alloyed stainless steels to the action of hydrogen. The interstitially dissolved nitrogen reduces the SFE, increases the rate at which partial dislocations occur, and slows down the movement of dislocations, or even anchors them. Because of this softening of the material at the crack tip is not possible, thus limiting the possibility of the crack's further growth through the action of hydrogen.