1. 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-NE ”
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.”

2. 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

3. Lockheed Martin Proprietary Information
DOE Nuclear Energy Enabling Technologies (NEET) Advanced Manufacturing Methods (AMM)
Contract: DE-NE
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

4. 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) N
Fuel Rod Cutaway
Fuel Pellets
Fuel Assembly
UO2 MOX
Clad
Fuel pellet
Fuel rod
Spacer grid
Water flow

5. 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

6. 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 (
Synthesis and Characterization of Austenitic ODS alloys (

7. Process Parameter Variation During Part Fabrication – Inconel 600

8. 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

9. 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

10. 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

11. 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

12. 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 # )
with phenol cure. (PhenoCure- part# )
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

13. 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

14. 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

15. 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

16. Back up slides

17. 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

18. 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 (
Synthesis and Characterization of Austenitic ODS alloys (

19. Literature Notes for Austenitic ODS Steel Composition(

20. Optical Image of Polished Cross-Section
Several Inconel 600 samples were metallographically cross-sectioned and polished
Examination of microstructure on sample 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
Top
Mid
Bot
~ 1cm Mt
JAB STAR Labs