The susceptibility of a high strength low alloy nanostructured steel to sulfide cracking resistance (SSCC) is assessed. Notch Tensile Slow Strain Rate (NTSSRT) method is used to evaluate the threshold stress intensity values (K_ISSCC)). The objective is to understand the effect of the microstructure on the susceptibility to SSCC, the control condition is a conventional low alloy carbon steel with a tempered martensite micro structure.

The tests were performed in a brine with 1% NaCl buffered at pH 4.5 with H₂S gas with 1% to 100% (mol %) balance N₂ at room conditions. The nanostructured steel results of the K_ISSCC parameter are: 107 Ksi in^0.5 at 1% H₂S to 42 Ksi in^0.5 at 100% H₂S. The control condition exhibited 22 Ksi in^0.5 at 100% H₂S. The evaluation of the relative crack propagation energy suggest that the nanostructured ferrite grains exhibit a much lower susceptibility to SSCC than the tempered martensitic microstructure