A study was made of the effect of applied stress on the stress corrosion crack morphology resulting from the exposure of Types 304, 309 and 316 austenitic stainless steel wire specimens to boiling 42 weight percent magnesium chloride solution. Crack morphology was dependent on applied stress; depth of crack penetration was inversely related to the applied stress while the crack density (cracks per unit length of specimen) increased with applied stress.
The area of greatest attack and failure was found to be in the material exposed to the vapor phase of the environment, slightly above the liquid-vapor interface. Differences in resistance of Types 304, 309 and 316 to stress corrosion cracking were minor, with Type 316 the most resistant and Type 304 the least. Introduction of air into the boiling solution reduced the time-to-failure. The effect of cold work on stress corrosion cracking resistance was found to be deleterious, with the most severe condition occurring at approximately 10 percent cold work.
The nature of stress corrosion cracking resulted in a rather wide dispersion of time-to-failure versus stress data points. In general, this dispersion increased with decreasing stress level or length of test.
