1994 Volume 43 Issue 3 Pages 126-133
Effects of alloying elements on stress corrosion cracking (SCC) resistance of 19Cr-9Ni steel in dilute NaCl solution were investigated. SCC tests were conducted with spot welded specimen in 50ppm Cl- solution at various temperatures, which allowed determination of critical temperature for SCC. Decreasing P content below 30ppm was effective in increasing SCC resistance. Critical temperature for SCC of 19Cr-9Ni steel with 10ppm P was 100°C, which was higher than that of 50°C for SUS 304 (0.07C-19Cr-9Ni-0.028P-0.027N). Addition of Cu had beneficial effect on SCC resistance. Critical temperature for SCC of 19Cr-9Ni-1Cu steel with 20ppm P was 140°C and that of 19Cr-9Ni-2Cu steel with 200-300ppm P was 100°C. Increasing N content had no significant effect on SCC resistance, while Mo showed detrimental effect on SCC resistance. Based on the corrosion morphology observations after immersion tests, competition was observed between SCC and crevice corrosion and SCC was enhanced under the condition which suppressed the dissolution by crevice corrosion. It is thought that beneficial effect of decreasing P content on SCC resistance is attributable to the result that it promotes metal dissolution in a crevice. On the other hand, addition of Cu makes the corrosion potential in a crevice more noble, resulting in increasing SCC resistance by making to shift to more noble potential region of the SCC occurrence.