Stress corrosion cracking of sensitized type 316 austenitic stainless steel in hydrochloric acid solution―effect of sensitizing time

摘要

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 316 was investigated as a function of sensitizing time (3.6 ks to 1.08 Ms at a sensitizing temperature of 923 K) and test temperature (333-373 K) in 0.82 kmol/m~3 hydrochloric acid (HCl) solution by using a constant load method. From the applied stress dependence of the three parameters (l_(ss), steady state elongation rate, t_(ss), transition time, t_f, time to failure), the relationships between applied stress and the three parameters were divided into three regions that are dominated by either stress, SCC or corrosion. In the SCC-dominated region, the log l_(ss) was a linear function of the log t_f regardless of applied stress and test temperature for each sensitized specimens, showing that l_(ss) became a useful parameter for prediction of t_f. Furthermore, the results obtained indicated that the degree of sensitization increased with increasing sensitizing time, reached a maximum at a sensitizing time of around 360 ks and then began to decrease at 1.08 Ms by Cr healing. On the basis of the results obtained, the effect of sensitizing time on SCC and the IGSCC mechanism were discussed.