Environmental Degradation of Additively Manufactured Alloys: Part I: 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 8:30 AM
February 28, 2022
Room: 201C
Location: Anaheim Convention Center

Session Chair: Jennifer Locke, OSU; Brendy Rincon, UTSA

8:30 AM Introductory Comments

8:35 AM  Invited
Corrosion of Additively Manufacture Magnesium Alloys: Nick Birbilis1; Zhuoran Zeng1; 1The Australian National University
    The production of additively manufactured magnesium alloys was achieved by laser powder bed fusion (LPBF). Herein, Mg-Al alloys that also include compositions with a hyper-loading of solute, are presented. The microstructure and corrosion behaviour of the specimens was characterised, and also contrast to the conventional alloy counterparts. The LPBF prepared specimens were shown to possess a unique microstructure comprising of fine grains and a crystallographic texture that was unique to cast or wrought Mg-alloys. Opportunities for optimisation of magnesium alloys using the LPBF process, including unique alloy compositions and the opportunity to directly generate components in net shape, are elaborated.

9:05 AM  
Effect of Post Processing Treatments on Corrosion Behavior of Laser Powder Bed Fusion(LPBF) 7050 Aluminum Alloy: Rupesh Rajendran1; Crosby Owens2; Preet Singh1; 1Georgia Institute of Technology; 2Northrop Grumman Corporation
    Recent advancements in nano-particle or inoculant addition has mitigated the problems of hot tearing and solidification cracking, which resulted in limited adoption of high-strength, additively manufactured(AM) 7xxx aluminum alloys produced by laser powder bed fusion(LPBF) process. However, a considerably small number of studies have focused on the corrosion behavior of such alloys. This work aims to explore the influence of microstructure on the corrosion behavior of AM 7050 aluminum alloy as a result of post-processing treatments. AM 7050 alloy in as-built, hot isostatically pressed, and differently heat-treated conditions are characterized and subjected to exposure and localized electrochemical tests like scanning vibration electrode technique(SVET). Potentiodynamic polarization and electrochemical impedance spectroscopy techniques are employed to understand the general electrochemical behavior. The overall corrosion susceptibility is compared to an equivalent wrought 7050 alloy, the results of which will be beneficial for consideration of these alloys for aerospace applications from a corrosion standpoint.

9:25 AM  
Corrosion Properties of AM A20X: Jamie Stull1; Courtney Clark1; Timothy Gorey1; Colt Montgomery1; Robin Pacheco1; Don Johnson1; Daniel Hooks1; 1Los Alamos National Laboratory
     As metal additive manufacturing (MAM) advances there are still limitations to the type of materials that can be manufactured. Aluminum alloys are one of the more difficult materials to build with AM. To address this issue there are new alloys of aluminum that are being developed. One of these is A20X, while chemically it is much different than the typical AlSiMg aluminum alloys, it has superior mechanical properties which are currently being studied. The change in chemical composition may aslo affect the roughness and corrosion properties compared to other AM alloys. In this study we will present the surface roughness of these alloys including SEM images of the as-built surface and compare to that of 316L SS, which is commonly printed across many machines. We will also present results on the susceptibility to corrosion of the as-built and electropolished material.

9:45 AM Break

10:00 AM  Invited
Impact of Chemistry and Microstructure on Corrosion Properties of Designed High-performance Stainless Steel Powder for Additive Manufacturing: Dana Frankel1; Abhinav Saboo1; Marie Thomas1; Jason Sebastian1; 1QuesTek Innovations LLC
    The unique microstructures resulting from selective laser melting (SLM)-based additive manufacturing (AM) of 17-4 stainless steel can lead to significant differences in corrosion performance of the additively manufactured material compared to typical wrought 17-4. QuesTek has developed an integrated computational materials engineering (ICME)-informed modeling framework to predict AM 17-4 microstructure and properties, applying this framework to design a modified 17-4 alloy with enhanced reliability and performance in the as-built and direct-aged conditions compared to standard commercial 17-4 powders. The presentation will describe results from corrosion testing including potentiodynamic polarization, salt fog testing, and rising step load (RSL) to assess the general corrosion properties, pitting behavior, and stress corrosion cracking performance for the designed 17-4 custom powder AM builds, commercial 17-4 powder AM builds, and wrought 17-4 under different heat treatment conditions. Insights regarding the relationship between chemistry, microstructure, and corrosion performance in both AM and wrought material will be discussed.

10:30 AM  
Surface Finishing Effects on the Corrosion Properties of Additively Manufactured 316L Stainless Steel: Courtney Clark1; Timothy Gorey1; Jamie Stull1; Don Johnson1; Randy Edwards1; Enkeleda Dervishi-Whetham1; Daniel Hooks1; 1Los Alamos National Laboratory
     Metal additive manufacturing (AM) continues to rapidly develop with advancements in mechanical and structural characterization of materials. However, characterization of material surface finish and its impact on material performance remains deficient. Early studies have shown that the surface quality of metal AM parts is extremely different compared to traditionally manufactured parts, and it is thought that these differences result in deviations of the observed corrosion properties. Among these are as-printed surface roughness, stability of the passive film, chemical composition of surface oxides, and microstructure.This study investigates the effects of varying surface finish on the corrosion properties of AM 316L stainless steel samples produced by direct metal laser sintering. To improve the surface finish and corrosion performance of the as-printed material, techniques including polishing, passivation, coatings, and heat treatment have been applied to 316L coupons. Fluctuations in corrosion performance due to build parameter modifications were also examined.

10:50 AM  
Exploring the Stress-corrosion Cracking Susceptibility of Additively Manufactured 316L in Boiling Magnesium Chloride: Erin Karasz1; Jason Taylor1; David Autenrieth1; Philip Reu1; Kyle Johnson1; Michael Melia1; Philip Noell1; 1Sandia
    Additively manufactured metal parts can exhibit high levels of residual stress leading to stress-corrosion cracking (SCC) susceptibility. We explore the relationship between residual stress and SCC susceptibility in laser powder bed fusion 316L stainless steel using an ASTM G36-94 boiling magnesium chloride experiment. The residual stress of the surface perpendicular to the build direction was controlled by cutting samples from the build plate at varying heights, ranging from 250 to 50 MPa in this study, and by heat treatments (600, 800, and 1200 C). All as-built samples showed SCC susceptibility. Samples heat-treated at or over 800 C exhibited reduced residual stress from their as-built counterpart and were free of SCC after >300 hours of immersion in boiling magnesium chloride. Annealing at 600 C showed similar SCC susceptibility to their as-built counterpart. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. SAND2021-7573 A