Hydrogen Induced Cracking and Stress Corrosion Cracking of Austenitic Stainless Steel under Mode Ⅲ Loading

Hydrogen induced cracking (HIC) of austenitic stainless steel under Mode Ⅲ loading could occur during dynamic charging of hydrogen and the threshold stress intensity was K_ⅢH/K_ⅢX=0.62. The torsional angle, i·e·, the torsional plastic deformation, enlarged continuously during dynamic charging under a constant torque, which corresponded with increasing the external torque Continuously, until the specimen was twisted to failure. In the flat fracture surface of the delayed failure, however, there wera some secondary cracks propagating along the planes inclined at 45°.
Stress corrosion cracking of austenitic stainless steel in a boiling MgCl₂. so lution could occur under Mode Ⅲ loading and the threshold value was K _Ⅲscc/K _ⅢX=0.13. The cracks, however, initiate and propagate along the planes inclined at 45° instead of the original notched plane, where there is no shear stress but the maximum normal stress.