Understanding The Effect of Shot Peening on Stress Corrosion Cracking of 316L Stainless Steel in High Temperature Water

Shot peening is commonly employed as a surface treatment to introduce compressive residual stresses and reduce susceptibility to stress corrosion cracking. In this work, the effect of SP was compared to surfaces that were polished to oxide polishing suspension to evaluate the effect of strain distribution on stress evolution and cracking of 316L stainless steel. Environmentally assisted cracking tests were conducted in high temperature, lithiated (2 ppm of Li added as LiOH) hydrogenated water (3 ppm of H₂) at 300 °C, using tapered samples that were subjected to strain rate tensile test until 4.5% average plastic strain achieved over ~850 hours.


Microstructural characterization of SP samples indicated a surface compressive stress up to 617 MPa and the material’s hardness increased significantly up to a depth of ~140 µm. However, microstructural characterization of SP did not reveal any phase transformation from austenite to martensite, but only the presence of an ultra-fine-grained layer (~2 µm thick) at the surface.

Post-test characterization of the SSRT samples revealed that SP did not significantly enhance SCC resistance of 316L SS. On the contrary, comparing the results with OPS polished samples, the SP treatment exhibited a detrimental effect, lowering SCC resistance of 316L SS, on the zone with greater strain value during the slow strain rate tensile test. This was evident from a higher crack density on the SP surface compared to the polished surface. The cross-section analysis showed that the crack formed in the tapered sample were intergranular in nature. These results are discussed in the context of plastic deformation, work hardening, and stress redistribution from compressive to heavily tensile regions during deformation, impacting SCC susceptibility.