Environmental Degradation of Additively Manufactured Alloys: Environmental Assisted Cracking, Material Degradation in Irradiated Environments
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee
Program Organizers: Kinga Unocic, Oak Ridge National Laboratory; Luke Brewer, University of Alabama; Sebastien Dryepondt, Oak Ridge National Laboratory; Michael Kirka, Oak Ridge National Laboratory; Jenifer Locke, Ohio State University; Xiaoyuan Lou, Purdue University
Thursday 8:30 AM
February 27, 2020
Room: 7A
Location: San Diego Convention Ctr
Session Chair: Michael Kirka, Oak Ridge National Laboratory; Xiaoyuan Lou, Auburn University
8:30 AM Invited
Stress Corrosion Cracking and Corrosion-fatigue Behavior of Additively Manufactured 17-4PH: James Burns1; Trevor Shoemaker1; 1University of Virginia
Additively manufactured (AM) components are being considered for use in high performance structural applications where environmental cracking behavior is often an important failure mode. As such it is critical to rigorously characterize the stress corrosion cracking and corrosion fatigue behavior of AM components of higher performance alloys such as 17-4PH. To this end the environmentally assisted crack growth rates (both da/dN vs ΔK and da/dt vs K) of wrought and AM 17-4 PH (at the same strength level) are characterized via linear elastic fracture mechanics testing in NaCl environments at various potentials. Differences in the growth rates and cracking morphology are interpreted in the context of a detailed characterization of the microstructure features of both the wrought and AM samples. These quantitative data and microstructure-based understanding will inform the efficacy of using AM components in structural applications and the modifications of the AM processing parameters to enhancing environmental cracking behavior.
8:55 AM
Stress Corrosion Cracking Growth Behavior of Additively Manufactured Alloy 800H in High Temperature Water: Jingfan Yang1; Miao Song2; Raul Rebak3; Xiaoyuan Lou1; 1Auburn University; 2University of Michigan Ann Arbor; 3GE Global Research
Alloy 800H (UNS No. N08810), also known as Incoloy 800 H, offers improved corrosion resistance and high temperature capability over 304/316 grade austenitic stainless steels in a variety of nuclear environments, including light water reactors. This paper reports a comprehensive study of the stress corrosion cracking (SCC) growth behavior of additively manufactured Alloy 800H in 288 C water. Three different heat treatment conditions were evaluated in this study, including stress-relief, hot isostatic pressing followed by solution annealing, and sensitization. These heat treatments present signature microstructural features that will be seen in an actual AM 800H component in service. The in-depth understandings of the unique role of AM microstructure on SCC growth will be discussed in detail, with comparisons to wrought 800H, AM and wrought 316L stainless steel. The effect of sensitization on SCC in AM material will also be revealed.
9:15 AM
Stress Corrosion Cracking Susceptibility of Additively Manufactured 2xxx-series Aluminum Alloys Produced by Selective Laser Melting (SLM): Kevin Chasse1; Preet Singh2; Jamshad Mahmood2; Crosby Owens1; Michael Van Order1; 1Northrop Grumman Systems Corporation; 2Georgia Institute of Technology
Two additively manufactured, 2xxx-series aluminum alloys (1.8 to 7.0% copper) produced by selective laser melting (SLM) were evaluated for stress corrosion cracking (SCC) susceptibility in chloride-containing environments relative to an AA2024-T3 wrought counterpart. Constant extension rate testing (CERT) were conducted in 3.5% NaCl and coupons were characterized following the test. The chloride concentration and effect of an oxidizer, i.e., hydrogen peroxide, were also studied using CERT. Polarization scans were used to assess the electrochemical behavior in the NaCl environments. Results of the experiments implied that the SLM alloys were mildly susceptible to intergranular SCC in chloride environments, but were less susceptible than their AA2024-T3 wrought counterpart. Electrochemical potential and the presence of hydrogen peroxide shifted the corrosion mode to intergranular corrosion and pitting. These SLM alloys are promising for aerospace applications where high strength and good corrosion resistance are required, however, SCC susceptibility could limit their implementation in structural applications.
9:35 AM
On the Implication of Strain Localization on the Fatigue Crack Propagation Under Hydrogen Pressure of LBM Inconel 718: Abdelali Oudriss1; Simon Puydebois2; Pierre Bernard3; Laurent Briottet2; Xavier Feaugas1; 1Université de La Rochelle - Lasie; 2CEA LITEN; 3ArianeGroup
This work aims to study the impact of hydrogen on the fatigue behavior of a nickel-base alloy 718 obtained by additive manufacturing. For that purpose, the microstructure was investigated, and fatigue tests were carried out in air, and under 300bar of H2. First, the striation spacing was examined by SEM on the fracture surface. Then, thin samples were extracted using FIB from regions containing striation to question the deformation mode associated to crack propagation with and without hydrogen. The results confirmed that the crack propagation rate is directly associated with the striation distance irrespective of the considered environment. Additionally, TEM observations have highlighted the fact that inter-shear bands spacing is correlated with the striation distance. Thus, the increase of crack growth rate under H2 is a direct effect of hydrogen which increases the dislocations sources number. These results are discussed in relation to the hydrogen embrittlement mechanisms in terms of hydrogen/plasticity interactions.
9:55 AM
Environmental Effects on the Stress Corrosion Cracking Behavior of an Additively Manufactured Stainless Steel: Jonathan Pegues1; Michael Roach2; Nima Shamsaei1; 1Auburn University; 2University of Mississippi Medical Center
Additive manufacturing is rapidly becoming a more viable means of advanced manufacturing of structural parts across a wide range of applications including biomedical, aerospace, nuclear, and defense sectors. Stainless steels, with their exceptional toughness and resistance to corrosive environments, are a popular choice for additive manufacturing across several industries. The performance of these additive manufactured stainless steels in various environments, however, has not been fully characterized. To overcome this lack of knowledge, the stress corrosion cracking behavior of 316L stainless steel is investigated in dry nitrogen, distilled H2O, and 3.5% solution of NaCl. To understand the significance of the effect each of these environments has on the stress corrosion cracking behavior, a one-way ANOVA analysis is performed on the resulting strength and ductility ratios. Additionally, two way ANOVA analysis is also utilized to understand the interaction between test solution and test temperature.
10:15 AM Break
10:35 AM Invited
SCC and IASCC of Printed 316L for Use in the Nuclear Industry: Michael Mcmurtrey1; Xiaoyuan Lou2; Gary Was3; 1Idaho National Laboratory; 2Auburn University; 3University of Michigan
Additive manufacturing (AM) is an area of interest to the nuclear industry for its benefits over traditional manufacturing, such as the ability to create complex geometries without welds. However, the behavior/properties of AM metals are poorly understood, especially with respect to irradiation effects. For stainless steel nuclear components, irradiation assisted stress corrosion cracking (IASCC) is particularly important. This work examines the IASCC behavior of proton irradiated AM 316L steel (direct energy deposition and powder bed AM specimens) and wrought 316L steel strained in simulated BWR NWC water (288°C, 0.2 µS/cm). TEM, SEM, confocal microscopy and X-ray microCT were used to examine the specimens. This work found that the wrought 316L was more susceptible to IASCC than the AM steel, however, significant IASCC was observed in the AM steel when tested with the tensile axis parallel to the build direction. HIPing was found to improve the IASCC resistance of AM steel.
11:00 AM Invited
Additive Manufacturing (AM) of Steels for Extreme Environments- Opportunities and Challenges: Niyanth Sridharan1; Theresa Mary Green2; Stephen Taller2; Kevin Field1; 1Oak Ridge National Laboratory; 2University of Michigan Ann arbor
Generation IV reactors use advanced designs with high fuel burnups which can lead to damage levels greater than 200 dpa. FM steels are candidate materials for such high dose applications because of their swelling resistance which has lead to significant interest within DOE and commercial businesses to explore the feasibility of advanced manufacturing (AM) of these materials. Due to the nature of the AM process, there is prima facie reason to hypothesize that FM steels fabricated via AM will have significantly different degradation mechanisms and kinetics compared to their wrought counter parts. This talk will focus on some of the fundamental and engineering aspects of degradation mechanisms (ion beam damage in particular) in commercial FM steels fabricated using state-of-the-art additive manufacturing techniques. In addition, this talk will also set the stage for future R&D activities towards development of FM steel variants tailored specifically for high dose applications using AM techniques.
11:25 AM
Comparison of Voids Swelling in Additively Manufactured and Cold-worked 316L SSs After Self-ion Irradiations at Elevated Temperatures: Miao Song1; Li Jiang1; Youxing Chen2; Xiaoyuan Lou3; 1University of Michigan; 2University of North Carolina, Charlotte; 3Auburn University
Additively manufactured 316L SSs were originally thought to possess better irradiation resistance compared to its coarse-grained counterpart. However, recent results from proton and Fe ion irradiations both show an enhanced swelling in additively manufactured 316L SSs over its coarse-grained counterparts. These observation leads to the confusion about the role of coldwork or substructure in voids swelling. Here, we investigated six structure variants of 316L SSs including variants with 0, 10%, 20% and 40% coldwork, variants with ultrafine grained structure, variants with cell structure produced by additive manufacture. These alloys were irradiated with Fe2+ ions to 50dpa at elevated temperatures. Voids welling were systematically characterized by the STEM dark field technique. While revisiting the effect of coldwork on swelling, this study also provides new insight in the similarity or not of cold worked structure and additively manufactured structure with a specific emphasis on voids swelling behavior in ion irradiated 316L SSs.