Environmental Degradation of Additively Manufactured Alloys: Aqueous and Atmospheric Corrosion I
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Kinga Unocic, Oak Ridge National Laboratory; Jenifer Locke, Ohio State University; Sebastien Dryepondt, Oak Ridge National Laboratory; Brendy Rincon Troconis, University of Texas at San Antonio; Andrew Hoffman, Catalyst Science Solutions; Xiaoyuan Lou, Purdue University
Wednesday 8:30 AM
March 22, 2023
Room: Sapphire 400A
Location: Hilton
Session Chair: Jenifer Locke, OSU; Xiaoyuan Lou, Auburn University
8:30 AM Invited
Electrochemical Behavior of Laser Powder Bed Fusion FeCrAl Alloys: Rupesh Rajendran1; Rajnikant Umretiya2; Vipul Gupta2; Richard Blair2; Andrew Hoffman2; 1Georgia Institute of Technology; 2GE Global Research
FeCrAl alloys are leading candidate materials for accident tolerant fuel (ATF) cladding applications in light water reactors (LWR) and have shown high resistance to hydrothermal corrosion, high temperature steam oxidation, fretting, and creep behavior. To take advantage of the versatility offered by the additive manufacturing process and to expand on the applications space, C26M (Fe12Cr6Al2Mo) samples were fabricated via laser powder bed fusion (LPBF) process. Previous studies have shown that AM FeCrAl alloys have excellent resilience to high temperature steam oxidation in nuclear reactor accident scenarios. In our work, the electrochemical behavior of the samples was studied in 3.5% NaCl environment using cyclic polarization and electrochemical impedance spectroscopy techniques. The results are compared with equivalent alloys manufactured via cast and forged and powder metallurgical routes to understand how the difference in microstructures as a result of processing routes affect the electrochemical behavior.
9:00 AM Invited
Influence of Feedstock on Corrosion of Additively Manufactured 316L Stainless Steel: Venkata Bhuvaneswari Vukkuma1; Ahmed Darwish1; Steven Storck2; Rajeev Gupta1; 1North Carolina State University; 2Johns Hopkins University Applied Physics Laboratory
The microstructure and properties of the additively manufactured alloys are influenced by the feedstock powder. In this research, 316L stainless steel test coupons have been produced using 316L stainless feedstock procured from multiple sources as well as modified using ball milling with additives. The role of the feedstock on the microstructure was investigated using a scanning electron microscope, X-ray diffraction, and transmission electron microscope. Corrosion behavior was studied using cyclic potentiodynamic polarization tests and constant immersion tests. The microstructure and corrosion of the test coupons were dependent on the characteristics of the feedstock.
9:30 AM
Corrosion Mechanisms of Additively Manufactured 316L Stainless Steels in Chloride Solutions: Thomas Voisin1; Shohini Sen-Britain1; ShinYoung Kang1; Yuliang Zhang1; Zhen Qi1; Nathan Keilbart1; Penghao Xiao2; Seogkoo Cho1; Yakun Zhu1; Rongpei Shi1; Y. Morris Wang3; Roger Qiu1; Brandon Wood1; 1Lawrence Livermore National Laboratory; 2Dalhousie University; 3University of California Los Angeles
Additively manufactured 316L stainless steel (316L SS) using laser powder bed fusion technique (L-PBF) exhibits an excellent resistance to pitting corrosion in chloride solutions. Pitting potential of the L-PBF 316L SS can be up to 4 times higher than the conventional, well annealed counterpart. In this talk, we will first present a detailed multi-scale characterization of the microstructural features unique to L-PBF 316L SS. In a second part, we will present our investigations on the mechanisms associated with pitting on the as-built and well-polished surfaces. We will show that pitting is due to local chemistry variations created during the melting and solidification. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Authors acknowledge the support of the Laboratory Directed Research and Development (LDRD) program (20-SI-004) at LLNL.
9:50 AM
Local Corrosion Initiation Sites of Additively Manufactured Selective Laser Melted 316L Stainless Steel: Alex Mirabal1; Ilker Loza-Hernandez1; Daniel Hooks1; Jamie Stull1; 1Los Alamos National Laboratory
Additive manufacturing (AM) is capable of producing unique, complex structures rapidly. The fast local melting of metal AM parts cool quickly due to the small area, providing unique microstructures, pores, and larger surface roughness compared to cast. AM microstructures change mechanical and chemical properties, such as strength, toughness, and corrosion, compared to traditionally manufactured parts. Variations in build parameters and composition creates a complicated, feature dependent, corrosion response. Mapping local corrosion, by scanning vibrating electrode technique (SVET), correlates position dependent local potential with ion concentrations. <br><br>Corrosion events can be linked to features on the surface, including grains, particles on the surface, cracks, and/or material composition. An AM 316L parallelogram demonstrated skin dependent corrosion. In situ SVET measurements confirm the corrosion dependence on surface roughness features. Mechanisms of local corrosion will be discussed regarding surface features. The understanding of the contribution of corrosion causing features will inform print parameter selection.
10:10 AM Break
10:30 AM
Localized Corrosion of Additively Manufactured Stainless Steel in Atmospheric Environments: Peter Renner1; Erin Karasz1; Kasandra Escarcega-Herrera1; Michael Heiden1; Michael Melia1; 1Sandia National Laboratories
Susceptibility to localized corrosion of laser powder bed fusion (L-PBF) stainless steels has been a topic of intense research for the past several years however little has been published on their atmospheric corrosion response. For many cases, atmospheric corrosion conditions will be more common than full immersion conditions and present environment variability that are hard to replicate. Pit characteristics of L-PBF and wrought stainless steel samples will be compared after exposure to different combinations of constant humidity (40/76% relative humidity) and salt loading (20/300 µg/cm2 of NaCl and artificial sea water). The impact chemical heterogeneities, inherent to the L-PBF as-printed microstructure and surface, have on local corrosion susceptibility will be explored. Atmospheric corrosion response of as-printed surfaces will be presented and reveal a distinct corrosion attack morphology from their polished counterparts of the same material.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2022-8864 A
10:50 AM
Structure and Semiconducting Properties of the Passive Film Formed on Additively Manufactured 316L Stainless Steel: Gary Halada1; Jason Trelewicz1; Mingxi Ouyang1; Nylette Lopez1; Jurek Sadowski2; Ryan Hulchanski3; 1Stony Brook University; 2Brookhaven National Laboratory; 3Clarkson University
The ultrathin passive layer formed on stainless steel is critical to corrosion performance, acting as a kinetic and electronic barrier to ingress of aggressive ions such as Cl. Understanding this layer, and in particular its homogeneity and its transport properties, enable us to determine the impact of additively manufactured alloy microstructure and post-print heat treatment on electrochemical properties and hence performance in service conditions. 316L stainless steel printed via Laser Powder Bed Fusion with variations in print parameters and post-print heat treatment (which result in variations in dislocation density and surface stress) are polarized in 0.1M HCl and the resulting passive layer studied via Mott-Schottky analysis, laboratory-based X-ray Photoelectron Spectroscopy, and synchrotron-based X-ray photoemission electron microscopy and low energy electron microscopy. The results show a correlation between passive film structure, electronic and transport properties, and underlying alloy print-formed microstructure which can facilitate design of AM alloys for enhanced environmental performance.
11:10 AM
Corrosion Behavior of 7050 and 7075 Aluminum Alloys Processed through Reactive Additive Manufacturing: Vikrant Beura1; Antriksh Sharma1; Yashaswini Karanth1; Kiran Solanki1; 1Arizona State University
In this work, a laser powder bed fusion (L-PBF) based reactive additive manufacturing (RAM) method has been used to process aluminum 7075 and 7050 alloys. Titanium and boron carbide was added as reactive particles during processing resulting in a crack-free, refined, and random textured microstructure. X-ray diffraction, Scanning and Transmission Electron Microscopy (SEM/TEM), and Energy Dispersive Spectroscopy (EDS) techniques were used for microstructure characterization. RAM 7075 showed precipitation of sub-micron to nanoscale Zn-Cu, Cu-Fe, and Mg-rich phases, while RAM 7050 showed Mg-Cu and Mg-Zn rich phases along the grain boundaries. A comparative corrosion response between wrought and RAM alloys was studied by electrochemical measurements such as potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and atomic emission spectroelectrochemistry analysis (AESCE). A reduction in corrosion resistance was observed with precipitation of excessive reactive particles in RAM alloys compared to wrought counterparts. Post-corrosion microstructures were analyzed to elucidate the underlying corrosion mechanism.