Study of Stress-Corrosion Cracking on 304 Stainless Steel by Wedge Opening Loading Method and Acoustic Emission Technique

One wedge opening loading system was setup to study the stress-corrosion cracking of 304 stainless steel. Acoustic emission sensors were attached on the surface of the sample in order to allow real-time recording of acoustic activity occurring in the material during the test. The whole process of the WOL test mainly included tearing of the residual ligaments, localized macroscopic deformation ahead of the crack tip and crack propagation, crack opening and further localized deformation in the front of the crack tip. The cracking mode in present study is a mixture of intergranular stress corrosion cracking and transgranular stress corrosion cracking. Most of acoustic emission signals are characterized as the signal of continuous waveform. Cumulative hits of continuous acoustic emission signals were mainly caused by the macroscopic deformation ahead the crack tip and the intergranular stress corrosion cracking whereas the occurrence of the burst signals could be attributed to the ligament tearing caused by transgranular cracking. Crevice corrosion resulted in the acidification of the crack tip and the occurrence of the corrosion pits on the crack surface.