NSUF 24-5082: Interactions between Neutron Irradiation and Oxide Based Inclusions in Additively Manufactured Austenitic Stainless Steels

Additive manufacturing (AM) provides an innovative process route for producing complex core components in the current and future pressurized water (PWR) and boiling water (BWR) reactor fleets. A number of these components are fabricated from austenitic stainless steels and are exposed to long-term high neutron fluences. While austenitic stainless steel are widely used in the wrought condition, the processing conditions characteristic of AM processes, such as powder bed fusion and directed energy deposition, are significantly different, thus producing different microstructures and mechanical properties.

The use of metal powder feedstocks, however, is introducing a range of additional uncertainties, particularly in the composition, with high levels of oxygen and nitrogen being commonly encountered in as-deposited materials. Oxygen composition can also have a marked effect on the microstructure and material properties in AM materials. Due to their high surface area and low volume, metallic powder feedstocks are prone to absorb oxygen and have a significantly higher oxygen content than their wrought counterparts. Since the oxygen composition is frequently not specified in wrought alloys, it is typically not measured in the powder feedstocks. AM processing of these high oxygen containing powder feedstocks can have implications on the microstructural evolution in as-deposited and post-processed AM materials. The oxygen composition of powder feedstock has led to the formation of oxide inclusions within the microstructures of austenitic stainless steel alloys fabricated through PBF processes.

This project will investigate the effects of neutron irradiation on the microstructure and mechanical properties of AM processed austenitic stainless steels using powder bed fusion and directed energy deposition techniques. Changes in the powder feedstock composition, primarily involving oxygen, nitrogen, and carbon, and the corresponding impact of neutron irradiation on the formation and composition of oxide inclusions and the regions surrounding them will be investigated using a range of tools. By characterizing the regions surrounding these inclusions and correlating microstructures with mechanical properties, the governing mechanisms for neutron damage in AM fabricated materials can be determined. Microstructural evolution from the atomic through the macro scale and the corresponding impact on mechanical properties will be explored to support the development of material standards for inclusion of AM components in existing and future PWR and BWR reactor fleets.

Additional Info

Field	Value
Award Announced Date	2024-08-15T09:40:56.137
Awarded Institution	Pennsylvania State University
Facility Tech Lead	Alina Montrose, Catou Cmar
Irradiation Facility
PI	Todd Palmer
PI Email	[email protected]
Project Type	RTE
RTE Number	None