Stress corrosion cracking (SCC) is the result of the combined influence of tensile stress and
a corrosive environment on a susceptible material. Austenitic stainless steels including types
304L and 316L are susceptible alloys commonly used in nuclear weldments. An engineered
residual stress field can be introduced into the surface of components that can reliably produce
thermo-mechanically stable, deep compressive residual stresses to mitigate SCC. The stability
of the residual stresses is dependant on the amount of cold working produced during surface
enhancement processing.
Three different symmetrical geometries of weld mockups were processed using low
plasticity burnishing (LPB) to produce the desired compressive residual stress field on half of
each specimen. SCC testing in boiling MgCl2 was performed to compare the LPB treated and
un-treated 304L and 316L stainless steel weldments. X-ray diffraction residual stress analyses
were used to document the respective residual stress fields and percent cold working of each
condition. Testing was performed to quantify the thermo-mechanical stability of the residual
stresses. The un-treated weldments suffered severe SCC damage due to the residual tension
from the welding operation. The results show conclusively that LPB completely mitigated SCC
in the tested weldments and provided thermo-mechanically stable, deep residual compression.
KEYWORDS:
Stress Corrosion Cracking, Low Plasticity Burnishing, Residual Stress, Weldments, Nuclear Reactor, Stainless Steel.