Laser Direct Manufacturing of Nuclear Power Components Dr. Jyotsna Iyer, Dr. Scott Anderson, Gautham Ramachandran, Georgina Baca, Scott Heise, Dr. Slade Gardner 3 November 2014 Acknowledgment: “This material is based upon work supported by the Department of Energy , Office of Nuclear Energy, Idaho Operations, under Award Number DE-NE0000542” Disclaimer: “This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.”

Nuclear Energy in the U.S. 104 reactors in the U.S. providing 20% of our electricity 4 new plants under construction in U.S., >60 globally, >150 on order Current Light Water Reactors (LWR) cost $10B-$12B/unit Costly on-site construction Next generation Small Modular Reactors (SMR) estimated $800M-$2B/unit DOE SMR program funding ~$400M B&W and NuScale selected for concept development Factory fabrication, rapid installation Advanced materials and manufacturing are significant industry drivers Advanced/Affordable Manufacturing methods are key enablers for competing in $700B global market

Lockheed Martin Proprietary Information DOE Nuclear Energy Enabling Technologies (NEET) Advanced Manufacturing Methods (AMM) Contract: DE-NE0000542 POP: 36 months, GFY13 - GFY15 DOE Team: Alison Hahn (HQ), Jack Lance (HQ), Bradley Heath (HQ) LM Team: Gautham Ramachandran, Dr. Scott Anderson, Dr. Jyotsna Iyer, Georgina Baca, Scott Heise, Dr. Slade Gardner Dr. Eric Faierson, Quad City Manufacturing Laboratory Scope HIGHLIGHTS Purpose: Position U.S. to compete in $B international market for nuclear power via enabling technology that significantly reduces development and operational costs and manufacturing lead time for nuclear reactors Project Objectives: Demonstrate >50% cost and schedule reduction using additive manufacturing methods. Develop, advanced radiation tolerant alloys via nanophase modification during additive manufacturing for reduced life cycle costs. LM CE&T Energy IPT funding cost-share and supporting industry engagement and growth opportunities Net-Shape Manufacturing Demo Articles built in <18 hours, no assembly/joining required – Fuel rod spacer grids manufactured using 316L SS and Inconel600 Technical Approach Build manufacturing demonstrations of complex parts demonstrating design flexibility and shortened design-to-manufacturing cycles Employ nanophase alloy modification via Laser Direct Manufacturing (LDM) to create enhanced radiation tolerance in the components Demonstrate the cost and schedule benefits through case studies and business case analyses Lockheed Martin Proprietary Information

Background for Alternate Nuclear Materials Selection Generations II-III Sodium Fast Reactor Molten Salt Reactor Gas Fast Reactor Lead fast Reactor Superficial-Water-Cooled Reactor Very High Temperature Reactor 1400 Temperature (°C) 1200 100 800 600 400 200 50 150 Displacements Per Atom (dpa) N13137-02 Fuel Rod Cutaway Fuel Pellets Fuel Assembly UO2 MOX Clad Fuel pellet Fuel rod Spacer grid Water flow

Table of Comparison Criteria for Selection of Alternative Nuclear Materials Alternate Nuclear Materials Low neutron absorption Elevated temperature mechanical properties Creep resistance Long-term stability Compatibility with reactor coolant Resistance to irradiation-induced damage (greater than 200 dpa) Radiation hardening and embrittlement Void swelling Creep Helium-induced embrittlement Phase instabilities BASELINE: Traditional ferritic/martensitic steels (HT-9) or later generations of F/M steels OPTION 1: ODS steels to examine effect of direct manufacturing methods on nanoscale oxide domains OPTION 2: Inconel 800 series of materials to study the effect of processing parameters offered by direct manufacturing methods to improve performance under irradiation OPTION 3: Among the refractory alloys, the Mo (TZM) alloys. These have a high operating temperature window and also, the most information on irradiated material properties Based on customer feedback at Technical review, materials down-selected to 316SS, ODS steels and Inconel alloys

Material Down selection for DM Demonstration Alloys: Inconel 600, Inconel 718, Incoloy 800, 316L SS, ODS Steels Oxides: Yttrium, Cerium - Mix of nano- & micron- sized oxide particles selected for mixing 3 x 3 Grid 10 x 10 Grid 10 x 10 Grid Emerging literature in Austenitic ODS alloys Development of Austenitic ODS Strengthened Alloys for Very High Temperature Applications (http://energy.gov/sites/prod/files/2013/09/f2/Stubbins_Austenitic%20ODS%20NEUP.pdf) Synthesis and Characterization of Austenitic ODS alloys (http://www.mme.iitm.ac.in/murty/?q=node/96)

Process Parameter Variation During Part Fabrication – Inconel 600

Process Parameter Effect on Fabricated Part Density – Inconel 600 8.47 g/cc is nominal Inconel 600 Density Laser power of 195W makes the fabricated article almost insensitive to scan speed

Process Parameter Effect on Fabricated Part Density – Inconel 718 8.19 g/cc is nominal Inconel 718 Density Laser power of 165W most consistent for Inconel 718; more scatter in density data

Microstructure Characterization QCML manufactured 56 of Inconel 600 samples Fourteen were selected Five samples were selected for microstructure characterization Sample #12 was selected for mounting in both the x-y & z directions for a total of six samples Metallography Procedure Mount/ grind/ polish Micrograph (photographs) Scanning Electron Microscopy (SEM) Etch Micrograph SEM Samples produced at the higher speed rate and lower power demonstrate more voiding based micrographs

Backscattered Electron Imaging of Sample 600-195-1400 Top Bottom INCONEL alloy 600 is a stable, austenitic solid-solution alloy. The only precipitated phases present in the microstructure are titanium nitrides, titanium carbides (or solutions of those two compounds commonly called cyanonitrides), and chromium carbides. Titanium nitrides and carbides are visible in polished microspecimens at magnifications of 50X or greater. They appear as small, randomly dispersed, angular-shaped inclusions. The color varies from orange-yellow for the nitride to gray-lavender for the carbide. These nitrides and cyanonitrides are stable at all temperatures below the melting point and are unaffected by heat treatment. At temperatures between 1000° and 1800°F (540° and 980°C), chromium carbides precipitate out of the solid solution. Precipitation occurs both at the grain boundaries and in the matrix. Because of the grain-boundary precipitation, the corrosion behavior of INCONEL alloy 600 is similar to that of other austenitic alloys in that the material can be made susceptible to intergranular attack in some aggressive media (sensitized) by exposure to temperatures of 1000° to 1400°F (540° to 760°C). At temperatures above 1400°F (760°C) the predominant carbide is Cr7C3. Below 1400°F (760°C) the Cr23C6 carbide is also present. Middle BSE imaging revealed the solidification/grain microstructure Microstructure appeared similar in the three locations examined No titanium nitride particles were detected (titanium nitride particles are typically found in wrought material) Black areas in images are voids

Microstructure Comparison of Inconel 600 Bar Stock Sample vs Additive Manufactured Sample QCML manufactured 56 of Inconel 600 samples Fourteen were selected Five samples were selected for microstructure characterization Metallography procedure Mount/ grind/ polish Micrograph (photographs) Scanning Electron Microscopy (SEM) Etch Micrograph SEM Mounting details: the mounting material is an epoxy resin (EpoMet G – part #20-3380-064) with phenol cure. (PhenoCure- part# 20-3200-080) Specifically: 5mils of Buehler EpoMet G powder (black) 20-25mils of Buehler PhenoCure powder (red) The press used is called Buehler SimpliMet 3000 Automatic Mounting Press The parameters are:  150C with 4200psi – 2min 30sec heat time and 5min cool down. SEM: do we have? Field Emission, JEOL JSM7001-FLV Scanning Electron Microscope (SEM). In addition to secondary, backscattered and low vacuum imaging, this SEM has a Scanning Transmission Electron Detector (STEM) that produces an image somewhat similar to one obtained with a Transmission Electron Microscope (TEM). In high vacuum, on clean gold samples, the specified resolution is 1.2 nm at 30kV and 3 nm at 1kV. Other materials will have less resolution. The magnification range is from 40X to 1,000,000X. Low vacuum mode allows for examination of non-conductive materials without coating with gold. The SEM also offers quick chemical analysis using Energy Dispersive Spectroscopy (EDS). This unit is made by Thermo Fisher (NORAN System Six). The x-ray detector is a 30mm2 Si(Li) crystal, with 134eV resolution at Mn. Etchant used: 30 second Electrolytic Oxalic Acid Etch Inconel 600: Sample 500X BSE 10kV not etched Inconel 600: Bar Stock Sample 500X BSE 10kV not etched Noticeable Grain Structure differences due to manufacturing process

Examination of Microstructure of Edge Transition Top Edge: Terminating Side (a) (b) Top Edge:500X Terminating Side Side (c) Top Edge Transition: 500X Sample 14 – equiaxed grain size at edge – equiaxed having approximately equal dimensions in all directions —used especially of a crystal grain in a metal. (Read paper). Most likely the growth initiating side. Initiating Side Side a) Inconel 600 Micrographs show (b) top edge (c) transitions (d) interior of sample at 500X (d) Away from edge: 500X

Test Coupons Ready for Mechanical Testing This build layout produces 45 test coupons in a single build at 1100mm/s and 195W The test coupons are cylinders with 0.5" diameter by 3" length.  15 cylinders are in horizontal orientation 15 cylinders are in vertical orientation 15 cylinders are at 45 degrees with respect to the horizontal. Inconel 600 longitudinal, transverse, and 45deg specimen blanks after LDM This build layout produces 45 test coupons in a single build and is the maximum number that can be produced in a single build on the available build platform. The test coupons are cylinders with 0.5" diameter by 3" length.  15 cylinders are in horizontal orientation, 15 cylinders are in vertical orientation and 15 cylinders are at 45 degrees with respect to the horizontal. Can we write about the mechanical test: Samples heat treated (900C for 1-2hr) to remove after fabrication to prevent warping

Next Steps Mechanical & microstructural characterization of test coupons for Alloy 600 Test specimen build for Alloy 718, Alloy 800 Characterization of Alloy 718 & Alloy 800 test specimens Test coupon build for Alloy 718 & Alloy 800 Mechanical & microstructural characterization of test coupons for Alloy 718 & Alloy 800 ODS steel mechanical blending & trial runs

Back up slides

Metallurgy of AM Technologies Weldable alloys are readily manufactured via AM Titanium alloys, stainless steels, alloy/tool steels, nickel-based alloys (Inconel), cobalt-based alloys Enables unique control of microstructure Very fine grain sizes due to high solidification rates Can produce microstructures not possible using conventional manufacturing methods Equivalent or superior mechanical properties to wrought alloys

Material Down Selection for DM Demonstration Mix of nano- and micron- sized oxide particles selected for mixing with 316SS Emerging literature in Austenitic ODS alloys Development of Austenitic ODS Strengthened Alloys for Very High Temperature Applications (http://energy.gov/sites/prod/files/2013/09/f2/Stubbins_Austenitic%20ODS%20NEUP.pdf) Synthesis and Characterization of Austenitic ODS alloys (http://www.mme.iitm.ac.in/murty/?q=node/96)

Literature Notes for Austenitic ODS Steel Composition (http://energy.gov/sites/prod/files/2013/09/f2/Stubbins_Austenitic%20ODS%20NEUP.pdf)

Optical Image of Polished Cross-Section Several Inconel 600 samples were metallographically cross-sectioned and polished Examination of microstructure on sample 600-195-1400 was conducted using backscattered electron imaging (BSE) Sample was not yet etched BSE images were taken in the three locations shown below Optical Image of Polished Cross-Section Sample 600-195-1400 Top Mid Bot ~ 1cm Mt 14.046 8-7-14 JAB STAR Labs