engleski

Investigations into the stress corrosion cracking of stainless steel alloyed with nitrogen

The resistance to stress corrosion of austenitic stainless steel alloyed with nitrogen (ASS N25) was determined in comparison with AISI 316L steel. The research into stress corrosion cracking was performed by using corrosion elongation curves in a 50% CaCl2 solution, at 100°C, under axial tensile loadings defined as various percentages of Rp0, 2, and with anodic polarization at a current density of 1.0 mA/cm2. The increased resistance of the nitrogen-alloyed steel to stress corrosion is based on the occurrence of NH4+ ions, and the repulsive action of the negatively charged nitrogen atoms towards the Cl- ions on the interface between the passive layer and the corrosion medium. Additionally, the interstitially dissolved nitrogen is able to accelerate the local deformation hardening of the material at the crack tip, for which reason the critical stress needed for stress corrosion to occur, or for further growth of the crack if it has already occurred, is increased.

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