From Lambda Technologies
Alloy 600 penetrations in several pressurized water
reactors have experienced primary water stress
corrosion cracking near the partial penetration Jwelds
between the Alloy 600 and the cladding on the
inside diameter of the components. The
microstructure and tensile properties indicated that
the Alloy 600 was susceptible to primary water stress
corrosion cracking (PWSCC) providing that a high
tensile stress (applied + residual) was present.
The residual stress distributions at the inside diameter
surface and at different depths below the surface were
measured in two Alloy 600 heater sleeve mockups.
Surface residual stresses ranged from 340 to 690
MPa. For the most part, the residual stresses
decreased with increasing depth below the surface.
For the heater sleeve mockups, the percent cold work
(i.e. true plastic strain) and yield strength as a
function of depth were determined. As a result of
pre-reaming and welding the heater sleeves, the
amount of plastic strain and yield strength increased
to a nominal depth of 0.025 cm. The true plastic
strain and yield strength decreased with increasing
depth below the surface.
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