Abstract
The Advanced Materials and Manufacturing Technologies (AMMT) program is aiming at the faster incorporation of new materials and manufacturing technologies into complex nuclear-related systems. An integrated approach, combining advanced characterization, high-throughput and accelerated testing, modeling and simulation including machine learning and artificial intelligence will be employed. While 316H (Fe-16-18Cr-10-14Ni-2-3Mo-0.04-0.1C) has been identified as a key alloy to be integrated into the AMMT accelerated alloy qualification approach due its relevance for many current and future nuclear energy reactors, many other alloys could be considered for the advanced fabrication of innovate high-performance nuclear components. Argonne, Idaho, Oak Ridge, and Pacific Northwest National Laboratories (ANL, INL, ORNL and PNNL) are collaborating on identifying the most promising alloy candidates relevant for the AMMT program. A selection criteria matrix was established to evaluate the alloys considering their relative importance and technological readiness levels for nuclear energy applications, with a focus on laser powder bed fusion (LPBF). Due to the broad range of potential candidate alloys, ORNL and INL focused on Ni-based alloys, while ANL and PNNL mainly evaluated Fe-based alloys. PNNL previously published materials scorecards reports on several key alloys and this report is providing a broader overview of Fe- and Ni-based candidate alloys, expending beyond alloys well-known to the nuclear community.
Among the Ni-based alloys, alloys 718, 625 and 282 (Fe-20Cr-20Co-8Mo) were considered the most promising alloys due to their printability, superior properties, significant amount of existing data, availability of commercial powder feedstock, and industry experience in fabricating complex components. All these alloys received great scorecards, while most of the other Ni-based alloys could not be evaluated in detail due to lack of information on additively manufactured (AM) versions of these alloys. Generating data on molten salt resistant Hastelloy N or Haynes 244 should be considered in the future as these alloys might be key to the development of molten salt reactors.
To assess the integration of alloy 282 into the AMMT digital manufacturing framework, ORNL performed the rapid optimization of alloy 282 printing parameters on a Renishaw 250 machine, the fabrication of sufficient materials for extensive characterization and mechanical testing both at ORNL and INL and added the printing data into the digital platform via the Peregrine software. INL conducted an annealing study to determine the optimum heat treatment for LPBF 282 and concluded that 1h at 1180°C would result in grain size after recrystallization that should provide a balance between the creep and fatigue property of the alloy. In additional, a detailed analysis of the LPBF 718 alloy was also conducted, with creep specimens being tested at 600-650°C and characterized by advanced electron microscopy. The alloy superior creep strength confirmed that LPBF 718 is a promising candidate alloy for the AMMT program. All these results were used to provide the AMMT leadership team with clear recommendations on the down selection of reactor materials, as well as establish a roadmap for the qualification of these selected alloys.
