Contribution of acoustic emission to the understanding of sulfide stress cracking of low alloy steels

The acoustic emission technique was applied to standard tests devoted to evaluate sulfide stress cracking susceptibility of steels for oil and gas industry. The mapping of the density of AE signals vs. their location on the specimen gauge length as a function of time allowed early detection of cracking, and gave meaningful information on incubation times and propagation rates. Sulfide stress cracking initiation was correlated with the presence of critical surface defects. A mechanism involving plastic strain and/or metal dissolution was proposed to account for crack propagation.

► SSC standard test was monitored by acoustic emission.
► Density of AE signals vs. their location and the time of test is represented.
► One obtains quantitative information on both initiation time and propagation rate.
► SSC involves hydrogen embrittlement together with local plastic strain and/or metal dissolution.