SCC damage identification of 718 alloy, obtained by laser powder bed fusion (LPBF) in simulated PWR medium

Abstract

The maturity of additive manufacturing technologies makes them potentially applicable to the manufacture of parts that can be integrated into nuclear reactors. Nevertheless, as far as their durability is concerned, it is important to take into account the possible damage that these parts could undergo in service, in particular when they are subjected to brittle degradation. The resistance to Stress Corrosion Cracking (SCC) of alloys used in the nuclear sector is continuously studied and optimized, but this is not yet the case for alloys developed by additive manufacturing for which little data is available. The present study aims to identify the similarities and differences in terms of resistance to SCC between an Alloy 718 obtained by the Laser Powder Bed Fusion (LPBF) process and its rolled counterpart in Primary Water Reactor (PWR) media. From an experimental point of view, this comparison is based on the behavior of loaded blades in three- point bending at a very slow displacement rate up to a similar total deflection. The results obtained with characterization at different scales, showed that LPBF 718 has a better resistance to SCC than Std 718. They also allowed to highlight the microstructural elements affecting the stress corrosion resistance and offer interesting prospects regarding LPBF Alloy 718 in nuclear applications.