Environmental Degradation of Additively Manufactured Alloys: Part II: Low Temperature/Aqueous Corrosion, Stress Corrosion Cracking, Pitting, Metal Dissolution
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, Purdue University; Elizabeth Trillo, Southwest Research Institute; Andrew Hoffman, GE Research; Brendy Rincon Troconis, University of Texas at San Antonio

Monday 2:00 PM
February 28, 2022
Room: 201C
Location: Anaheim Convention Center

Session Chair: Elizabeth Trillo, SWRI; Xiaoyuan Lou, Auburn University

2:00 PM  Invited
AM Stainless Steel 316L in Corrosive Environment: Features Controlling Pitting and Metal Dissolution : Thomas Voisin1; Rongpei Shi1; Shohini Sen-Britain1; Zhen Qi1; Yuliang Zhang1; Seongkoo Cho1; Yakun Zhu1; Josh Kacher2; Ibo Matthews1; Y. Morris Wang3; Roger Qiu1; Brandon Wood1; 1Lawrence Livermore National Laboratory; 2Georgia Institute of Technology; 3University of California Los Angeles
     We will present our recent investigations of the performance of additively manufactured 316L stainless steel (AM316L SS) in corrosive solution (NaCl, HCl). Testing different AM316L SS, we show that the rapid solidification-induced chemical heterogeneities and the process-induced high surface roughness do not prevent the as-built material from far exceeding the pitting potential of the conventional 316L SS. Corrosion properties seem to vary with microstructure and oxide thickness. We will first introduce the multi-scale microstructural features that are present in the as-built and annealed AM 316L SS. The second part will intend to answer what is controlling the pitting nucleation and the subsequent metal dissolution. We use a multi-scale experimental and theorical approach with in situ electron microscopy, galvanic corrosion testing, atom force microscopy, ion mass spectroscopy, and phase-field simulations. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

2:30 PM  
Environmental Susceptibility of EBM Ti-6Al-4V as a Function of Print Direction in Seawater: Matthew McMahon1; Nicholas Pizzolato1; Fatou Cisse1; Eric Dau1; William Golumbfskie1; 1Naval Surface Warfare Center, Carderock Division
    Ti-6Al-4V is a popular alloy for aerospace, oil and gas, biomedical, and naval applications due to its high corrosion resistance, light weight, and high strength. This alloy has proven compatible with additive manufacturing processes such as electron beam melting (EBM), which through powder bed heating can produce parts with relatively low residual stress and high toughness compared to similar AM methods. These attributes make EBM a desirable AM processing route for marine components, though numerous questions remain concerning differences in environmental susceptibility in comparison to legacy processing methods. This effort aims to understand the corrosion and stress corrosion susceptibility of EBM Ti-6Al-4V in seawater conditions as a function of print direction. Emphasis will be placed on porosity and surface characteristics for evaluation of flow-assisted corrosion, pitting, and stress corrosion susceptibility. Comparison will be drawn to conventional castings in order to identify optimization opportunities for marine EBM Ti-6Al-4V components.

2:50 PM  
Tribo-corrosion Degradation of Additively Manufactured Multi-principal Element Alloy.: Jibril Shittu1; Maryam Sadeghilaridjani2; Mayur Pole3; Sundeep Mukherjee3; 1LLNL; 2Arizona State University; 3University of North Texas
    Tribo-corrosion degradation accelerates material degradation in a multitude of environments beyond the single effect of wear or corrosion. In a bid to extend the service life of structural conventional alloys, multi-principal element alloy (MPEA) developed with additive manufacturing (AM) offers a plethora of possibilities in current and emerging structural applications. With the possibility to suppress elemental and phase segregation coupled with microstructural refinement achieved with AM, reduced wear rate, enhanced regenerative passivation, noble corrosion potential and ultimately better tribo-corrosion resistance of current MPEAs are viable potentials. This presentation will compare the tribo-corrosion response of single-phase FCC CoCrFeMnNi HEA LENS additively manufactured, and vacuum-arc melted, in 3.5 wt.% NaCl solution at room temperature. Highlight of this study promotes the potential of utilizing additive manufacturing of MPEA for use in extreme environments that require a combination of tribo-corrosion resistance, mechanical durability, extended service life and net shaping with low dimensional tolerance.

3:10 PM  
Microstructure and Corrosion Behavior of 309L Stainless Steel Clad onto Carbon Steel Using Wire-fed Directed Energy Deposition: Scott Bozeman1; O. Isgor1; Julie Tucker1; 1Oregon State University
    This work uses a wire-fed directed energy deposition (DED) additive manufacturing technique to apply relatively thin (~0.5 mm) 309L stainless steel claddings onto 1018 carbon steel substrates to increase corrosion resistance and save material cost. First, we determine the impacts of processing parameters (laser power, travel speed, wire feed, stepover, and cover gas) on clad morphology, microstructure, and metallurgical bonding. Parameter sets free from cracks, pores, and inclusions are then down-selected for further material testing. Chemical composition and hardness profiles are measured across the clad-substrate interface. The claddings are electrochemically tested in boric acid electrolytes to simulate corrosion in nuclear power systems. Localized corrosion testing at the clad-substrate interface is performed to assess galvanic corrosion of the dissimilar metal couple. The electrochemical behavior is connected to the interfacial composition gradients and the unique microstructures formed during cladding.