Stress Corrosion Cracking Growth in Additively Manufactured 316L Stainless Steel

Additively manufactured (AM) metals have opened exciting pathways for versatility and agility, both in the creation of previously unavailable geometries and with the ability to create rapid repairs nearer to the components which need repairing. For components with metals which were originally selected for stress corrosion cracking (SCC) resistance, AM replacements will need to display equal or slower SCC growth rates to the traditional wrought equivalent. Testing was performed in this work to observe the susceptibility of AM 316L stainless steel (SS) to SCC in both deaerated pure water and aerated, ion faulted conditions at temperatures of 350 – 680°F (177 – 360°C). Testing was split across active load facilities running multi-phase, multi-condition compact tension (CT) specimens and flowing autoclaves with single-condition CT specimens passively stressed in compliance self-loaded ring fixtures. Effects of orientation, temperature, environment, and some different processing conditions will be discussed. Results indicate superior SCC resistance in the AM 316L compared with its wrought counterpart when tested one-on-one in the same autoclave. A clear orientation dependence was observed, with X-Z (i.e. Crack growth in the direction of dendritic grain growth) having the highest growth rates among AM specimens. In general, both wrought and AM 316L displayed significant resistance to crack propagation, which made it difficult to achieve representative crack growth rates for average material behavior. Techniques which were used or will be used in future AM 316L SCC testing to mitigate this crack stalling or poor crack engagement will be discussed. Overall AM 316L SS makes a very promising material for use where typical 304/304L or 316/316L wrought is already employed with regards to its impressive SCC growth resistance.