• Cerjak, Horst-Hannes
• Böllinghaus, Thomas
• Roos, Eberhard
• Dorsch, Thomas
• Enzinger, Norbert
• Saarinen, Kari

Abstract

After publication of the court’s expert results1 , it became an important point to consider stress corrosion cracking as a governing mechanism in the catastrophic failure of the Cleuson-Dixence pressurised shaft in December 2000. Therefore the already running investigations to quantify steel S890 concerning strength, toughness, microstructure and weldability was expanded to enable also the investigation of the fracture behaviour of steel S890 and its weldments in several distinguished environments. Several laboratory tests were performed to characterise the crack initiation and crack propagation in air, water and in simulated worst case situation in H2 S saturated water. Three and four point bending specimens in water with different pH values as well as the worst case situation were performed to characterise the crack initiation behaviour. Slow strain rate tests were performed in different environments with different microstructures to characterise the susceptibility of S890 and its weldments to stress corrosion cracking under several environmental conditions. To validate the results of fracture mechanical CT tests in air and water WOL specimens were exposed to water and to H2 S saturated water. These tests showed, that stress corrosion cracking can be excluded as the governing mechanism of the catastrophic failure of the CD pressurised shaft.<br/>After this substantial program also some original material containing cracks was made<br/>available. These original cracks were characterised and found to be hydrogen induced cold<br/>cracks instead of stress corrosion cracking confirming the previously obtained results

Topics

• microstructure
• crack
• strength
• steel
• Hydrogen
• susceptibility
• pH value
• stress corrosion