Stress corrosion cracking of austenitic stainless steel Type 316 in acid solutions and intergranular SCC mechanism: effects of anion species (Cl? and SO4?2? and sensitizing temperature

摘要

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 316 was investigated as a function of sensitizing temperature (800–1300 K) in 0.82 kmol/m3 sulphuric acid (H2S04) and 0.82 kmol/m3 hydrochloric acid (HC1) solutions at 353 K by using a constant load method. The three parameters (lss, steady state elongation rate; tss, transition time; tf, time to failure) were obtained from corrosion elongation curves and were divided into three regions of applied stress, irrespective of sensitizing temperature and anion species, which are dominated by either stress, SCC or corrosion. In SCC-dominated region, lss became a relevant parameter for prediction of tf although the slope depended on the sensitizing temperature. The maximum applied stress, the minimum applied stress and the value of tss/tf in the SCC-dominated region depended upon sensitizing temperature in both solutions. Specifically, at a sensitizing temperature of ≈950 K the maximum applied stress was smaller in 0.82 kmol/m3 H2S04 and larger in 0.82 kmol/m3 HC1 than that of the solution annealed specimens. In addition, sulphate ions were found to become more aggressive than chloride ions for the SCC susceptibility of the specimens with the most severe sensitization. On the basis of the results obtained, the effects of sensitization on SCC, the role of anion species (S042 and Cl) and an intergranular SCC mechanism were discussed.