SUMMARY

316 stainless steel (SS) used in nuclear applications are subjected to high temperature low cycle fatigue (LCF) and creep-fatigue (CF) cycles. Conventionally manufactured 316 SS at this high stress-temperature environment have been studied by many with the use of CF damage interaction diagrams featured in various high temperature code cases: RCC-MRx, ASME, R5, etc. On the other hand, material acceptance challenges are present for additively manufactured (AM) materials. These materials can have large variation in microstructure depending on AM methodology, machine, and building specifications. This can lead to material behaviors that are different from materials manufactured through conventional methods. Currently, no material acceptance criteria for high stress-temperature environments have been placed on AM components.
This study explores the LCF and CF behavior of directed energy deposited (DED) AM 316H SS to develop a rapid test material acceptance criteria for this type of AM material. Preliminary LCF and CF studies on wrought 316L SS are conducted at a temperature range of 550 to 700°C, where a strong focus is placed on a testing temperature of 650°C. Tensile or compressive peak dwells of up to 30 minutes are used. Preliminary test results are used to establish a test matrix for DED AM 316H SS of varying build parameters. Tested samples are analyzed with the TF and DE damage life prediction models and microscopy techniques in the mesoscopic-microscopic scale to develop the material acceptance criteria.