Material Development for Electron
Beam Melting
Timothy Horn
Tjhorn.ims@gmail.com
Center for Additive Manufacturing and Logistics
http://camal.ncsu.edu
• Material is only used where it is needed • Significant reductions in buy-to-fly ratio • Significant savings in fuel
• No tooling or dies needed to fabricate a part = short runs, small batches, legacy parts • Point of use process - reduced inventory -reduced
carrying and transport costs
• Combine assemblies into single parts
• Extremely complex geometries not possible with traditional methods (geometric lattice structures, conformal channels )
• Structurally optimized components-unique properties (thermal, electrical, biological etc.)
• Material is only used where it is needed
• Significant reductions in buy-to-fly ratio
• Significant savings in fuel
• No tooling or dies needed to fabricate a part = short runs, small batches, legacy parts
• Point of use process - reduced inventory -reduced carrying and transport costs
• Combine assemblies into single parts • Opportunities for materials development
Advantages of Additive Manufacturing
• GRCop-84 • OFE Copper • Niobium • C103 Niobium • Beryllium Alloys • Ti-Al • Nickel Alloys (625, 718, M247) • Tool Steels • Aluminum Alloys (6061, 7075, 2024) • Nitinol (55%, 60%) • Ti6Al4VB • Metal Matrix Composites • Lunar Regolith
•Clean room facility houses bio-plotter
•Direct metal additive fabrication research
Current Research Areas Include: •Structural Optimization
•Biomedical applications/custom implants
•New materials development, parameter optimization, process mapping
•Energy absorption/attenuation, negative Poisson structures •Fatigue/creep and other mechanical properties (characterization) •Surface finish/powder removal/residual stresses
•Machining of components to specified tolerances •Supply chain and Logistics of additive networks
Electron Beam Melting (ARCAM)
• 4kW Electron beam is generated within the electron beam gun
• The tungsten filament is heated at extremely high temperatures which releases electrons
• Electrons accelerate with an electrical field and are focused by electromagnetic coils
• The electron beam melts each layer of metal powder to the desired geometry • Vacuum/melt process eliminates
impurities and yields high strength properties of the material
• Vacuum also facilitates the use of highly reactive metals
• High build temperature provides good form stability and low residual stress in the part
• 20-200 micron layer thickness • 20-300 micron powder
Safe”
• Wafer Supports • Contours
• Hatch
Electron Beam Melting (ARCAM): Parameter Development Strategy
2. Material Properties 3. Powder Properties 1. Feasibility 4. Hardware Changes•
Toxicity, PPE, Exposure Limits
•
X-Ray Generation
•
Regulations (ITAR)
•
Minimum Ignition Energy
Chronic
Beryllium
Disease
(CBD)
www.adinex.be Modified Hartmann Tube: Minimum Energy (Joules) from a capacitor discharge to ignite a dust cloud of known density in 1 out of 10 tries•
Melting Temperature
•
Thermal Conductivity
•
Electrical Conductivity
•
Vapor Pressures
•
Phase Diagrams
•
TTT Diagrams
•
Known Heat Treatments
Electron Beam Melting (ARCAM): Parameter Development Strategy
2. Material Properties 3. Powder Properties 1. Feasibility 4. Hardware Changes•
Powder Morphology
•
Powder Flow
•
Internal Porosity
•
Apparent Density
•
Powder Size Distribution
•
Sintering Characteristics
Type Average Volumetric Flow Rate (cm3/s) Powder A 0.599 Powder B 0.704 Powder C 0.699C
•Apparent Density •Size •Shape •Surface Contamination 99.99% Cu99.99% Cu 99.80% Cu ASTM B855-06
Flow rate is a good indicator of
powder raking, packing, feeding characteristics!
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0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% <60 60-100 100-220 220-500 Size Range (microns)
P e rc e n ta g e ( b y w e ig h t)
•
Powder Morphology
•
Powder Flow
•
Internal Porosity
•
Apparent Density
•
Powder Size Distribution
•
Sintering Characteristics
Electron Beam Melting (ARCAM): Parameter Development Strategy
2. Material Properties 3. Powder Properties 1. Feasibility 4. Hardware Changes•
Powder Quantity
•
Raking characteristics
•
Thermal considerations
•
Powder Quantity
•
Raking characteristics
Electron Beam Melting (ARCAM): Parameter Development Strategy
Preheating Parameters: Smoke Test
•
Beam Focus Offset (mA)
•
Line Offset (mm)
•
Line Order
•
Beam Current (min, average,
ramping) (mA)
•
Beam Speed (mm/s)
•
Box Size
•
Average Current
•
Number of Reps
1
2
3
Line Offset
Line Order
Beam Speed (mm/s) 400, 800, 1500, 2000 Beam Current (mA) 8-20
Speed Function*
T=Working temperature (750C)
Z = melt depth (mm) P = beam power (W)
θm = temperature rise to melting point (C)
κ = thermal conductivity (W/mm- C) d = beam diameter (mm)
v = beam velocity (mm/sec) ρ = density (gm/mm^3) c = specific heat (J/gm- C)
dv c
P Z m 1 . 0 UI E dv Electron Beam Melting (ARCAM): Parameter Development Strategy
Melting Parameters: Hatch
Porosity Secondary Parameter Search: •Contour Parameters •Hatch Settings •Temperature Stability •Turning Point Function •Thickness Function Melt pool
quality continually observed by operator!
(72 to 79 % IACS for cathode)
•Field Testing: Verified performance under high power RF conditions
Electron Beam Melting (ARCAM): Applications-High Purity Copper
•High average power Normal Conducting Radio Frequency (NCRF) photoinjectors.
•Accelerators for high-energy electron-beam applications • Requires 99.99% pure copper
• (Conductivity >100% IACS ~5.8 x10^7 S/m )
•A key problem limiting the duty cycle of NCRF photoinjectors is inefficient cooling
Two medium-beta SNS cryomodules in assembly at JLab Fundamental Power Coupler HOM Coupler Medium Beta Cavity
•Superconducting Radio Frequency (SRF) Accelerators are now considered the device of choice for many applications in high energy and nuclear physics. - Energy Recovery Linacs (ERLs) Linear Colliders (ILC) Neutrino Factories Spallation Neutron Sources.
•After the Accelerating Cavity, the Fundimental Power Coupler (FPC) is considered the most important component in the SRF accelerator. - The FPC transfers power from the RF source to the accelerating cavity
•Vacuum, Cryogenic, and High Power Electromagnetic Environment •Must also dissapate hundreds of kW of average power
Electron Beam Melting (ARCAM): Applications-High Purity Niobium
Pressure Monitored by RGA
•Stanford Research Systems
•Quadrupole mass spectrometer sensor
•Upstream particle filters •Small Quantity of Powder
•Very High Temperature: 2477 °C
Average RRR Average Tc Average ΔTc
Sample A 18 9.19 0.09
Sample B 19 9.16 0.12
Samples are superconducting:
• RRR values ~ ½ of reactor grade bulk material.
• Transition temperatures are ~ 0.11 K below bulk value.
• Sample B has a slightly lower Tc on average than sample A
• Transition Width (ΔTc) is consistent with other measured bulk
samples
• Sample A has clean transitions for all four samples measured.
• Sample B has a two step transition for the two samples measured.
Electron Beam Melting (ARCAM): Nitinol Ni-Ti
Increasing Beam Current
<24°C = Martensitic 37°C= Austenitic
Electron Beam Melting (ARCAM): GRCop-84
•
2009: Development of new
pre-alloyed parameter set
•
2013: High Niobium Ti-Al- Mercury
Center
Electron Beam Melting (ARCAM): Ti-6Al-4V B
•
One of the key problems with EBM fabrication of
Ti-6Al-4V is the large columnar β grain growth
Jump safe
Melt safe
•
Could Boron additions help control microstructure in
EBM produced Ti-64?
~40
Layers
refine or disrupt the columnar
microstructure of EBM fabricated parts
•
TiB2 did not go into solution
•
Resulted in relatively poor mechanical
properties
• In 2012 ATI was able to provide us with pre-alloyed Ti-6Al-4V with trace amounts of Boron.
• The Ti-6Al-4V powder shows a typical lath structure, the Ti-6Al-4V-1B powder has a homogenous structure that exhibits dendritic patterns.
• Properties of Ti-6Al-4V and Ti-6Al-4V-1B samples fabricated with the Arcam Electron Beam Melting process using the available process parameters for Ti-6Al-4V
Ti-6Al-4V
Ti-6Al-4V-1B
We would like to thank ATI for developing and providing the Ti-6Al-4V +B powder used in these tests!
Electron Beam Melting (ARCAM): Ti-6Al-4V B
•
Develop predictive models for process
parameters
•
Development in process monitoring
technologies
Acknowlegements:
Dr. Denis Cormier
Dr. Tushar Mahale
Dr. Ola Harrysson
Dr. Harvey West
Pedro Frigola
Kyle Knowlson
Dr. Andrzej Wojcieszynski
Jean Stewart
