Chloride-Induced Stress Corrosion Cracking of Austenitic Stainless Steel

1. Chloride-Induced Stress Corrosion Cracking of Austenitic Stainless Steel David Spencer 3rd Year PhD Student Nuclear Department

2. Area of Concern Submarine PWR Primary Circuit • Austenitic Stainless Steel – 304L • Chloride Ions – Cl- • Tensile Stress – Applied or Residual

3. Crack propagating across grains Grains Metallic Grains Crack propagating along metallic grain boundaries Crack Propagation Transgranular Intergranular

4. 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.

5. Bent Beam Test

6. Test Configuration

7. 2.5 Days 180MPa 3% Strain

9. Initiation at Pitting

10. Shallow Crack Propagation

11. Typical Crack Front Crack tip propagating to within 0.2mm of the far side of the specimen

14. Factorial Investigation

17. FIB Milled Section of Crack Tip

18. Any Questions? thanks to: Dr Ian Giles Dr Paul Chard-Tuckey Dr Mike Edwards

19. Corrosion Enhanced Plasticity Model The corrosion enhanced plasticity model Magnin et al.(1996)