Environmental Degradation of Additively Manufactured Alloys: High Temperature and Environmental Effects
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee, TMS: Additive Manufacturing Committee
Program Organizers: Kinga Unocic, Oak Ridge National Laboratory; Jenifer Locke, Ohio State University; Sebastien Dryepondt, Oak Ridge National Laboratory; Xiaoyuan Lou, Auburn University; Elizabeth Trillo, Southwest Research Institute; Andrew Hoffman, GE Research; Brendy Rincon Troconis, University of Texas at San Antonio

Tuesday 8:00 AM
March 1, 2022
Room: 201C
Location: Anaheim Convention Center

Session Chair: Kinga Unocic, ORNL; Sebastien Dryepondt, ORNL; Andrew Hoffman, GE Research, US

8:00 AM  
Long-term High-temperature Oxidation Performance of Inconel 625 Processed by Laser-assisted Additive Manufacturing: Grace De Leon Nope1; Juan Alvarado-Orozco2; Guofeng Wang1; Brian Gleeson1; 1University of Pittsburgh; 2CIDESI
    After achieving consistent microstructure of additive manufactured (AM) parts of Ni-based alloys, research efforts have focused on assessing mechanical and oxidation performance. Consistent oxidation performance at high temperatures is essential to continue the qualification of AM parts for their implementation in industrial applications. Previous work has demonstrated better oxidation resistance at short-term of wrought Inconel 625 than its AM counterpart. This study aims to investigate the long-term oxidation performance of AM Inconel 625 after isothermal exposure in lab air at 800C and 950C for up to 5000 h. Oxidation behavior of as-built AM, homogenization heat-treated AM, and wrought samples will be evaluated and compared. Oxidation kinetics, internal attack (i.e., internal oxidation and void formation), and chromia/alloy interfacial defects will be correlated to the microstructure prior to oxidation.

8:20 AM  
Metal Dusting Resistance of Additively Manufactured Ni-based Alloys: Influence of Post-processing Surface and Heat Treatments: Emma White1; Clara Schlereth1; Benedikt Nowak2; Heike Hattendorf2; Mathias Galetz1; 1DECHEMA Forschungsinstitut; 2VDM Metals
    Metal dusting (MD) attack occurs in carbonaceous atmospheres (ac>1) and temperatures of 400-800C, common in the downstream cooling stages of processing and syngas plants, and after an incubation period, causes rapid disintegration into fine coke particles. AM is of interest for MD applications as it could be used to replace corroded components on-demand, and where complex geometries would be beneficial. Advanced Ni-based alloy 699XA has been developed for MD environments and recently been adapted for AM processing. Alloy 699XA builds were tested under industrial MD conditions at 620C for 1000 hours with different surface conditions and heat treatments. The build post-processing effects on the pit formation and MD resistance will be discussed in relation to the onset mechanisms and the results compared with conventional wrought Ni alloys. This ‘topAM’ has project received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 958192.

8:40 AM  Invited
Hydrogen Trapping at Grain Boundaries and Dislocation Structures in Additively-manufactured Stainless Steel 316L Evaluated via SIMS/EBSD: Kaila Bertsch1; Peter Weber1; Shohini Sen-Britain1; Chris San Marchi1; Thomas Voisin1; Morris Wang2; Brandon Wood1; 1Lawrence Livermore National Laboratory; 2University of California- Los Angeles
    Stainless steel (SS) 316L is frequently used in hydrogen-rich environments due to its superior resistance to degradation and embrittlement. Additively manufactured (AM) SS 316L exhibits distinctive cellular microstructures with segregation that can fundamentally change the material response. Qualifying AM SS 316L components requires defining the interactions of these novel microstructures with hydrogen. In this study, hydrogen trapping was compared in deuterium gas-precharged AM SS 316L components in the as-fabricated state, after recrystallization annealing, and after annealing + prestraining to create equiaxed dislocation cells. EBSD orientation mapping of grain structures and orientations and backscattered electron imaging of AM dislocation structures was combined with ToF-SIMS/NanoSIMS compositional mapping to reveal the spatial distributions of hydrogen. The trapping ability of the AM dislocation structures with segregation were compared to that of conventional dislocation structures and that of high- and low-angle grain boundaries to evaluate the response of AM SS316L to use in hydrogen environments.

9:10 AM  
Sensitization of Austenitic Alloys Made by Laser Powder Bed Fusion: Jingfan Yang1; Laura Hawkins2; John Snitzer1; Xiang Liu2; Miao Song3; Lingfeng He2; Xiaoyuan Lou1; 1Auburn University; 2Idaho National Laboratory; 3University of Michigan
    This talk gives an overview of the current understandings of sensitization behavior of Alloy 800H and 316L stainless steels that are manufactured by laser powder bed fusion additive manufacturing (AM). The degree of sensitization (DOS) and carbide evolution will be discussed as the function of temperature, time, and microstructure. Different from conventional cast/wrought materials, the fast laser solidification resulted in non-equilibrium heterogeneous microstructures, including hierarchical boundary structures, ultrafine dislocation structures, and inhomogeneous element segregation, which further impact elemental diffusion, carbide nucleation and growth kinetics. AM austenitic alloys exhibited different sensitization/desensitization kinetics and corrosion behavior as compared to their wrought counterparts. The underlying sensitization mechanisms, including transport phenomena and carbide precipitation at elevated temperatures will be discussed. The mechanistic explanation focuses on the roles of dislocation cellular structures, boundary types, and carbon level.

9:30 AM Break

9:45 AM  
Pulsed Transient High Heat Flux Testing of Coated Alloys in Extreme Environments: Sanjay Sampath1; John Saputo1; Felipe Caliari1; 1State University of New York
    Many engineering applications currently seek to implement additively manufactured alloys in moderate to high temperature environments. In some cases, these alloys are directly exposed to combustion processes with a potential for severe environmental degradation alongside relatively large mechanical loads. While traditional test methods seek to understand a singular material behavior under controlled conditions, in reality these effects are often highly coupled and require a holistic multifunctional test method to understand the role of environmental degradation on the system. Here a test method for extreme environments coupling highly transient thermal loading with heating rates on the order of 10,000 C/min, heat fluxes on the megawatt scale, and a tunable continuously varying combustion environment is highlighted. The impact of this environmental degradation on alloys and coated alloy systems is explored in this context with the potential for coatings to extend the useful temperature range of both traditional and additively manufactured components demonstrated.

10:05 AM  
Transpiration Cooling of Additively Manufactured Porous Metallic Structures in High Heat Flux Environments: Kaitlyn Mullin1; John Martin2; Christopher Roper2; Carlos Levi1; Tresa Pollock1; 1University of California Santa Barbara; 2HRL Laboratories
    High heat flux environments, like those of atmospheric re-entry and fusion reactors, impose severe thermal gradients and high local temperatures. These conditions demand materials with exceptional thermal and structural durability. A scalable heat transfer method, such as transpiration cooling, can be integrated to manage these extreme heatloads. The employment of additive manufacturing (AM) enables fabrication of highly customized structures for optimal heat transfer. In this talk, transpiration cooling of a porous metallic AM architecture with a liquid water coolant will be presented as an effective means to disperse localized heat and maintain structural durability. A high heat flux testing facility, featuring a high powered laser, was developed to characterize structure cooling performance under extreme heatloads. The resulting thermal and oxidation behavior of the structure under these conditions will be discussed. Such tests provide insight to further tailoring the cooling efficiency and mechanical properties of these structures.

10:25 AM  
How Part Surfaces Influence Corrosion for a Laser Powder Bed Fusion 316L Stainless Steel: Michael Melia1; Erin Karasz1; Kasandra Escarcega Herrera1; Jason Taylor1; Samantha Rosenberg1; Paul Kotula1; Michael Heiden1; Jeffrey Rodelas1; 1Sandia National Laboratories
     The as-printed surface of 316L stainless steel parts produced via laser powder bed fusion (LPBF) is tortuously rough and chemically heterogeneous. This leads to variability in the materials surface properties such as susceptibility to local corrosion. This presentation explores the characterization and quantification of local corrosion susceptibility as it relates to roughness and surface chemistry for LPBF 316L samples. The oxide surface films that formed during the LPBF process were characterized with scanning transmission electron microscopy and energy dispersive spectroscopy, revealing a Si/Mn/Cr rich amorphous oxide that covers nearly the entire as-printed surface, which can lead to a significant increase (>500 mV) to the materials breakdown potential. The machined surface where a part was removed from the build plate was also investigated, showing a reduction in corrosion resistance by 2 orders of magnitude depending on cutting technique.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2021-7650A.