STRESS-CORROSION CRACKING OF STAINLESS-STEELS IN NACL SOLUTIONS

The straight-chromium ferritic stainless steels, two-phase ferritic-austenitic stainless steels and high-nickel solid solutions (like alloys 800 and 600) investigated are resistant to stress corrosion cracking at stress intensity (K//1) levels less than equivalent to 60 MN multiplied by (times) m** minus **3**/**2 in 22 pct NaCl solutions at 105 degree C. Martensitic stainless steels, austenitic stainless steels and precipitation hardened superalloys with about 18 pct chromium may be susceptible depending on heat treatment and other alloying elements. Molybdenum additions improve the resistance of austenitic stainless steels significantly. The fracture mechanics approach to testing of stainless steels yields results which are consistent with service experience and testing smooth specimens. The Copson curve is reproduced by plotting the stress corrosion threshold stress intensity (K//I//S//C//C) vs the nickel content of stainless steels with about 18 pct chromium.