Effect of stress on additive manufactured metals and their corrosion properties (SAMCO)

Important results from the project

The main objective of SAMCO was to promote the safe use of additively manufactured (AM) stainless steel (SS) components in the nuclear power industry by investigating the effect of post-treatment methods on the components´ resistance to stress corrosion cracking (SCC). The relationships between residual stresses, thermal oxides and the initiation and propagation of SCC were studied. The results of SAMCO showed that to ensure a high SCC resistance at AM SS-components, either hot isostatic pressing (HIP) or annealing is required.

Expected long term effects

The results, which are summarized in the technical report and six sub-reports, show that the finishing treatments required to ensure high SCC resistance at AM SS-components are either hot isostatic pressing or annealing. Pickling and shot blasting do not affect the SCC resistance but remove the thermal oxides. Differences in results between laboratory and field tests point to the need for new standards for evaluation SCC resistance of AM samples for the nuclear power industry.

Approach and implementation

The experiments were designed to investigate material limitations in terms of SCC after AM. Samples of 316L were printed in the desired shape and orientation. In particular, it was studied how different finishing methods (hot isostatic pressing, annealing, shot blasting or pickling) affected SCC initiation and propagation in AM materials. The SCC performance of AM materials was compared with conventionally manufactured materials. Microstructure, residual stresses and chemistry were analyzed using complementary techniques in the laboratory and at large-scale facility.