Environmental Degradation of Additively Manufactured Alloys: Aqueous Corrosion
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 2:00 PM
February 27, 2020
Room: 7A
Location: San Diego Convention Ctr
Session Chair: Jennifer Locke, Ohio State University; Luke Brewer, University of Alabama
2:00 PM
Cyclic Oxidation Behavior in Air at 950ºC of Hastelloy X Fabricated by Selective Laser or Electron Beam Melting: Sebastien Dryepondt1; Marie Romedenne1; Matthew Kuner2; Rishi Pillai1; 1Oak Ridge National Laboratory; 2Georgia Institute of Technology
2:20 PM
Understanding the Anomalous Corrosion Behavior of Additively Manufactured Stainless Steels through Multi-modal Synchrotron Techniques: Jason Trelewicz1; David Sprouster1; Gary Halada1; Hanfei Yan2; Yong Chu2; Eric Dooryhee2; Guhaprasanna Manogharan3; 1Stony Brook University; 2Brookhaven National Laboratory; 3The Pennsylvania State University
Additive manufacturing processes produce materials with hierarchical microstructures containing fusion boundaries at the macroscale, irregular grains and grain boundaries at the microscale, and subgrain dislocation structures at the nanoscale. In 316L stainless steels, corrosion performance has been discussed in the context of chemical heterogeneities formed in the presence of these hierarchical microstructures. However, the large variability in reported measurements underscores the need for statistically significant microstructural data, which is often difficult to access via electron microscopy alone. In this presentation, we explore multi-modal synchrotron x-ray techniques for quantifying hierarchical microstructures and their connection to the underlying chemical distribution in 316L stainless steel. Our results show that the dislocation density depends on the printing conditions with implications for the chemical distribution at the nanoscale. Corrosion rates and pit densities are then discussed to build a connection between printing conditions and corrosion performance vis-à-vis microstructural and chemical information from synchrotron measurements.
2:40 PM
Effect of Surface Contouring on Corrosion of 6061-RAM2 Produced by Laser-based Powder Bed Fusion Additive Manufacturing: Hamidreza Torbati-Sarraf1; Seyed Alireza Torbati Sarraf2; Amir Poursaee1; 1Clemson University; 2University of Southern California
This study provides micro-electrochemical and microscopic evidences on influence of contouring in additive manufacturing (AM) process of 6061-RAM2 material on corrosion resistance. Scanning electrochemical microscope (SECM) was exploited to create a pictorial distribution of dissolution rate from a cross section of cylindrical tensile bars processed by AM. Micro-electrochemical results in 0.01M NaCl and post corrosion microscopic observation revealed that contouring reduces porosity and increases integrity of the surface. This yields to better corrosion performance. However, deep key holes formed due to second melting and solidification of material, induces significant localized corrosion at cross-section of the bar.
3:00 PM
Issues in Localized Corrosion of Selective Laser Melted 316L: Duane Armell Macatangay1; Jonathan Skelton1; Wenhao Lin1; Robert Kelly1; Ji Ma1; 1University of Virginia
Stainless steels such as 316L produced by selective laser melting (SLM) have advantages in terms of design space for structures compared to conventionally processed material. However, the localized corrosion phenomena and mechanisms in SLM materials are not well understood. The microstructure in materials produced by SLM is significantly different from that of its wrought counterpart, resulting in the presence of numerous heterogeneities that can ultimately lead to localized corrosion. This study characterizes the dependence of melt-pool boundary attack and intergranular corrosion and assesses a series of microstructure-based mechanisms responsible for the corrosion of these SLM 316L alloys. Galvanostatic etching, potentiodynamic scans, mass-loss testing, and accelerated testing of wrought and SLM 316L were used to reveal the localized corrosion behavior in these alloys. Additionally, focused ion beam and transmission electron microscopy was utilized to understand the microstructural origins of these observations.
3:20 PM
Corrosion Properties of Additively Manufactured Duplex Stainless Steel: Greg Nigon1; O. Burkan Isgor1; Somayeh Pasebani1; 1Oregon State University
Additively manufactured duplex stainless steel 2205 components were built via selective laser melting and heat treated to obtain the duplex microstructure. Gas atomized duplex stainless steel 2205 powder (D90 <45m) was procured from Carpenter and characterized for morphology and particle size distribution. The parts were built using an OR Creator SLM machine with 250W Laser and nitrogen environment. The process parameters were selected for optimal density and microhardness. Solution annealing was done to obtain the dual phase microstructure. The microstructure was characterized by optical and electron microscopy. Ferrite content was measured by EBSD. Parts produced by SLM were characterized for corrosion properties with 3.5% NaCl used as the electrolyte. Characterization was done using the electrochemical tests of OCP monitoring, polarization resistance, potentiostatic EIS, and cyclic polarization. Comparisons were made between as-built and heat treated samples produced by SLM.
3:40 PM Break
4:00 PM Invited
Role of Microstructure and Surface Finish on the Corrosion of Selective Laser Melted 304 and 316 Stainless Steel: Eric Schindelholz; Michael Melia1; Rebecca Schaller1; Jesse Duran1; Jeffrey Rodelas1; 1Sandia National Laboratories
This presentation examines how the unique microstructural features and surface finish of SLM stainless steels affect corrosion resistance relative to their conventionally processed counterparts. Recent studies on the electrochemical behavior of SLM 316L and 304L in saline solutions will be discussed within the context of hierarchal microstructural and surface features governing corrosion resistance across multiple length scales. Global and local electrochemical methods, such as a capillary microelectrochemical cell, in combination with electron microscopy were used to correlate corrosion behavior to microstructure for both as-printed and polished material surfaces. The deleterious role of bulk material and surface defects, the exceptional pitting resistance enabled by ultrafine second phase inclusions, and the role of less obvious features such as melt pool boundaries will be discussed. Based on these studies, processing and post-processing targets for enhanced corrosion resistance are addressed along with areas for future work.
4:25 PM
Interaction between Additive Manufacturing Defects, Powder Contamination, and Two Corrosive Environments: Holly Martin1; Daniel Bogen1; Jeremy McKnight1; Brett Conner1; 1Youngstown State University
Small quantities of needed parts, for equipment that is no longer in production, can be made using additive manufacturing, at less cost and waste than large scale manufacturing methods. Defects caused by processing parameters that create voids and contamination from previously run powders can both produce locations that concentrate mechanical stresses and corrosive ions. Determining how these defects, both voids and contamination, interact with the base AlSi10Mg metal in corrosive environments is important, especially if these parts are planned for long-term applications. The research presented here will compare the behavior of parts produced using optimal parameters to parts with defects from either processing parameters or Inconel contamination in two corrosive environments – saltwater immersion and salt-fog. The various defect sizes and environments will be compared to determine how the processing parameters affect corrosion behavior and how corrosion affects mechanical behavior.
4:45 PM
Corrosion and Protection (Conversion Coating and Plasma Electrolytic Oxidation) of Ti6Al4V Processed by Powder Bed Fusion – Additive Manufacturing Electrochemical and EIS Study: Joseph Hazan1; Menachem Bamberger1; 1Technion, Israel Institute of Technology
Green conversion coatings has been developed using oxyanion like permanganate additive (a conversion layer former) to (H2SO4). An anodic oxide film by anodization (plasma electrolytic oxidation) has been also performed. The structure obtained for these two protective coatings consists of an outer (porous) layer, observed at high frequencies and an inner (barrier) layer at low frequencies in the impedance diagram. An electrical equivalent circuit describing the coated alloy is proposed. Electrochemical corrosion results in the corroding electrolyte (NaCl 3%) of Ti6Al4V will be presented and compared to that of a rolled (Ti-0.15 % Pd) foil. Finally, semi conductive properties of the passive film formed on the additive manufactured titanium alloy have been investigated. Mott-Schottky plots (CSC-2 vs. E) have been drawn and the donor concentration ND and the flat band potential EFB have been determined from the linear part and interpreted as regards passivation of the Ti alloy.
5:05 PM
Corrosion Behavior of 304L Stainless Steel Produced by Laser Powder Bed Fusion: Christopher Faraj1; Ho Lun Chan1; Jacob Benoun1; Vilupanur Ravi1; Zachary Hilton2; Joseph Newkirk2; 1California Polytechnical University, Pomona; 2Missouri University of Science and Technology
Austenitic 304L Stainless Steel (UNS S30403) is a favorable candidate for additive manufacturing (AM) because of its excellent weldability and is used in many industries including but not limited to chemical processing, medical, commercial and domestic applications. In this project, the microstructure and corrosion behavior of AM 304L Stainless Steel (SS) and its wrought counterpart were studied under three conditions: as-fabricated, heat treated at 700°C for 250 hours and heat treated at 800°C for 250 hours. Test coupons were electrochemically characterized in accordance with ASTM G59 and ASTM G61 protocols in a 3.5 wt% NaCl solution. Microstructural characterization was performed using optical & scanning electron microscopy and energy dispersive spectroscopy (EDS). The results of the electrochemical and microstructural characterization will be presented and discussed.
5:25 PM
Corrosion Behavior of Newly Developed High Toughness Mixed-phase Steels: Neetu Verma1; S. Sangal1; K. Mondal1; 1IIT Kanpur
Advanced steels based on bainitic or mixed-phase microstructures by proper choice of alloying represent promising candidate in alternative to conventional pearlitic steel for railway applications. In the present work, 0.61%C-1.71%Si-0.86%Mn steel has been used for the development of mixed-phase morphologies consisting of bainite, pro-eutectoid ferrite and retained-austenite by employing novel heat treatment strategies (continuous cooling followed by isothermal heat treatment). Corrosion behavior of these steels has been carried out in freely aerated 3.5wt.% NaCl solution. Dynamic-polarization, linear-polarization and immersion testing followed by detailed microstructural characterization of the surface before and after corrosion as well as the rust layer with the help of scanning electron microscopy, optical profilometry and Raman spectroscopy have indicated better corrosion resistance of the mixed-phase steel to pearlitic rail steel. The presence of higher degree of α-FeOOH in the rust phase as well as not-so-severe galvanic corrosion in the mixed-phase steels attribute to their better corrosion resistance.
5:45 PM
The Effects of Solution Chemistry on the Corrosion Behavior of Cold Sprayed AA7075: Ozymandias Agar1; Nicholas D’Attilio1; Luke Brewer1; 1University of Alabama
This presentation will describe how changes in solution pH and salinity affect the corrosion behavior of cold sprayed AA7075 materials. Cold spray is being developed to repair corrosion damage on aircraft structures, but the corrosion behavior of the deposited material is still under investigation. Samples of aluminum alloy 7075 were cold sprayed using helium gas onto wrought 7075-T651 substrates. Potentiodynamic testing was done in a variety of artificial seawaters modified from ASTM D1141 with pH ranges from 6.2 to 9.6. The chloride concentrations were varied from 0.3-0.9 molar. Potentiodynamic testing was performed in accordance with MIL-STD 889C with highly consistent results. Quiescent immersion testing with the same solutions is underway to examine pitting behavior. The polarization behavior of the cold sprayed material roughly matched that of wrought AA7075-T651 over the range of pH values tested. The cold sprayed materials tested thus far have outperformed wrought material in terms of pitting.