chloride-induced stress corrosion cracking of austenitic stainless steel david spencer 3rd year phd...

Chloride-Induced Stress Corrosion Cracking of

Austenitic Stainless SteelDavid Spencer

3rd Year PhD Student

Nuclear Department

Area of Concern

Submarine PWR Primary Circuit

• Austenitic Stainless Steel – 304L

• Chloride Ions – Cl-

• Tensile Stress – Applied or Residual

Crack Propagation

Crack propagating along metallic grain boundaries

Metallic Grains

Grains

Crack propagating across grains

Transgranular

Intergranular

Initial Development• Previous finite element study had shown that

anomalous crack propagation occurred at prior plastic strains of around 5%

• New atmospheric test developed to emulate chloride contamination on the exterior of primary circuit

• Conditions under which severe transgranular SCC occurred established

• Full factorial study planned to distinguish between the interacting factors controlling crack propagation rates.

Bent Beam Test

Test Configuration

2.5 Days 180MPa 3% Strain

Initiation at Pitting

Shallow Crack Propagation

Typical Crack Front

Crack tip propagating to within 0.2mm of the far side of the specimen

Factorial Investigation

Inputs Levels

Stress 60 MPa 120MPa

Strain 0% 0.5% 1% 2% 5%

Temp 60ºC 75ºC 90ºC

Humidity 30% 70%

FIB Milled Section of Crack Tip

Any Questions?

thanks to:

Dr Ian Giles

Dr Paul Chard-Tuckey

Dr Mike Edwards

Corrosion Enhanced Plasticity Model

The corrosion enhanced plasticity model Magnin et al.(1996)