Additive Manufacturing: Mechanisms and Mitigation of Aqueous Corrosion and High-temperature Oxidation: Corrosion Assessment of Additively Manufactured Parts I
Program Organizers: Amir Mostafaei, Illinois Institute of Technology; Yashar Behnamian, University of Alberta; Bryan Webler, Carnegie Mellon University

Wednesday 8:00 AM
October 20, 2021
Room: A112
Location: Greater Columbus Convention Center

Session Chair: Amir Mostafaei, Illinois Institute of Technology; Bryan Webler, Carnegie Mellon University

8:00 AM
SCC Behavior of IN 718 in BWR Conditions: Amanda Leong¹; Jinsuo Zhang¹; George Pabis²; ¹Virginia Tech; ²Nova Tech
    Additive manufactured Inconel 718 hold down springs can potentially serve as a replacement for 3-leaf spring. The design of AM hold down spring can be easily to modified to accommodate different fuel assembly and reactor designs, minimizing the upper core wear, reworking, and number of parts. This work discusses the stress corrosion cracking (SCC) behavior of hardened additively manufactured IN 718 in Boiling Water Reactor (BWR) environments at 288°C. The behavior of the material’s crack-propagation rate as a function of crack-tip stress-intensity was examined. Dissolved oxygen concentration in the environment has small effects on the crack-propagation rates. The material’s crack-propagation rates plateau at an average of 4x10⁻⁶ mm/s with max stress intensity factor measured at 63.6Mpa√m. Most cracks observed were intergranular cracks (IG) with some transgranular crack (IG) branching out from IG cracks.

8:30 AM
Environmentally Assisted Cracking of AM718 Wire Arc Additively Deposited AM 718 – Role of Processing and Microstructure: Ramgopal Thodla¹; Badri Naraynan²; Hannah Sims²; Ben Schaeffer²; ¹DNV; ²Lincoln Electric
    Environmentally assisted cracking (EAC) of AM 718 fabricated using wire arc additive manufacturing processes was studied under cathodic polarization. The effect of deposition path parameters for the arc deposition on starting microstructure and defect generation was assessed using systematic exploration of the operating space. The additive deposits were subjected to different heat treatments to optimize the microstructure for corrosion performance. The Kth values measured using rising displacement test methods were compared with those of wrought material tested under similar conditions. Crack growth rate measurements under constant K conditions over a range of potentials was also compared with the crack growth rate measured on wrought 718 under similar conditions. The EAC results were co-related with key elements of the microstructure of AM 718 i.e. ’/” strengthening precipitates, grain boundary  phase as well as other Laves phases present in the microstructure.

9:00 AM
Performance Evaluation of Oxidized Inconel 625 Made by Laser-assisted Additive Manufacturing: Grace De Leon Nope¹; Juan Alvarado-Orozco²; Guofeng Wang¹; Brian Gleeson¹; ¹University of Pittsburgh; ²CIDESI
    Inconel 625 (IN625) fabricated by additive manufacturing (AM) processes can exhibit pronounced niobium and molybdenum segregation in comparison to its wrought counterpart. Such a result can impact chromia-scale establishment behavior and subsurface microstructure evolution during high temperature exposures. This study focuses on evaluating the oxidation resistance and associated fatigue performance of IN625, comparing wrought and two AM processes (laser powder bed fusion and direct energy deposition). The results show that during high-temperature oxidation, the manufacturing process affects the amount of delta phase formation beneath the chromia scale as well as the internal attack depth and composition. The contributions of these subsurface features on fatigue crack initiation and growth are assessed. Elucidating the relationships between AM microstructure and crack growth will aid in advancing AM part design.

9:30 AM
Assessing the Printability and Oxidation Resistance of AM Built Al_xCoCrFeNi with Directed Energy Deposition: Jose Loli¹; Bryan Webler¹; Maarten De Boer¹; Jack Beuth¹; ¹Carnegie Mellon University
    Directed energy deposition (DED) systems enable in-situ composition control by alloying multiple powders together in a melt pool. This capability can be used to study the variation in printability and material properties. In this work, we focus on the material system AlCoCrFeNi which is a high entropy alloy that has been successfully printed in powder bed and DED systems. On arc-melted samples, this alloy has been characterized and has demonstrated good high temperature oxidation resistance. The printability response of Al_x(CoCrFeNi)_1-x (where x = 8, 12, 15, 20) is studied in detail by exploring different process parameters with the Trumpf TruLaserCell 3000 system to minimize defect formation. Additionally, the high temperature oxidation behavior of these additively manufactured samples is evaluated. Determining how composition variation affects ideal printing parameters and material properties is important to fully characterize new alloys in additive manufacturing. Our approach also expands the capabilities towards new material discovery.