Intergranular Stress-Corrosion Resistance of Austenitic Stainless Steels in Water/Oxygen Environment: Accelerated Test Procedure

A system for studying the stress-corrosion behaviour of materials loaded in uni-axial tension in water at 289° is described. Using this system,the stress-corrosion of austenitic stainless steels has been investigated in water containing 100 ppm dissolved oxygen. The experimental variables studied included heat-treatment, carbon content, and alloy composition.Annealed Type-304 stainless steel when stressed in uni-axial tension did not show any evidence of cracking even in the presence of high concentrations of hexavalent chromium ions. Sensitised Type-304 stainless steel (24 h at 595°) developed intergranular fracture in 17 hours. The time-to-failure in the sensitised condition was found to be a function of the carbon content of the alloy. Data obtained on carbon-containing alloys indicate that, below 0·03 wt.-% carbon, no stress-corrosion cracking occurs over a test period of 300 hours.Duplex alloys (austenite+ferrite) show no tendency to stress-corrosion cracking even at high carbon levels and after heat-treatment at 595° for 24 hours. Thick welded sections of Type-304 stainless-steel plate behaved in a similar manner to fully sensitised Type-304 stainless steel and developed intergranular fracture in 42 hours. Similar tests showed that welded Type-304L stainless steel was not affectedin this way.