2. Learning goals
• Finding out what DED is and it’s types
• Discovering where and when it’s used
• Determining why you should or shouldn’t use it
• How the technique works
3. What is Directed Energy Deposition (DED)
• Uses a focused energy source to melt materials and deposit them on
the workpiece, layer by layer.
• The sequence layer deposition is similar to that of an Extrusion
4. Materials Used and their Delivery Systems
• Materials Used
– Ceramics and Polymers.
– Typically metallics, either wire or powder feed form
• Fe, Ti, Al
• Inconel, Monel, Ti-6-4, Stainless Steels
• Energy sources
– Electron beam
– Plasma or Electric arc
– Hybrid - Arc and Laser.
5. What is DED - types & energy systems
• Wide range of techniques, terminologies and vendors
– Wire Arc (WAAM) & Wire Laser (WLAM)
– Electron Beam AM (EBAM) - EBW
– Beam Deposition (BD) - LENS, LDW
6. Where, When and why DED
• Any metal that can be welded can be 3D printed with DED
• Non-vertical material deposition is possible.
• Build substrate can be a empty flat plate or an existing part
onto which additional geometry will be added.
sources; Left RAMLABS - Right DMG MORI
7. Where, When and why DED
Creating complex shapes
• Cannot be manufactured by
Adding features to simple
• Complex structures which
would otherwise have a
high “buy to-fly” ratio.
8. How does it work - WAAM
• WAAM uses an arc welding process to 3D print metal parts.
• It uses a wire feeds exclusively.
• Material type and power source available determines usage of an
electric or a plasma arc technique.
9. How does it work - WAAM
• The wire, on melting, is extruded in the form of beads on the
• The beads stick together to create a layer of material.
• A robotic arm on a slider is used to deposit material.
11. Electron Beam AM (EBAM)
• An electron beam is used instead of a laser, in a vacuum chamber.
• Uses wire or powder feed.
• High speed electron stream bombards the material feed.
• Kinetic energy, turns into heat upon impact, causing fusion.
12. How does it work - EBAM
• No bead creation, direct melting
• 60 KeV KE of Emitted Electrons
• Power concentration
– 1kW - 10 MW/mm^2
• Powder size
– 45 - 100 μm
• Beam Current Range
– 1 - 50 mA
• Layer thickness
– 0.07 - 0.15 mm
13. How does it work - Laser Powder BD
• Inert carrier gas
• Powder size
– 20 - 50 μm
• Laser Power
– 1 - 36 kW
0.25 - 0.5 mm
0.1 - 5 mm
14. How does it work - Laser Powder BD
• Working distance - laser energy density is high enough to form a
• The powder is melted just as it enters the pool not during flight.
15. Proces control DED - Optical feedback
– Size and shape weld pool
– Cooling rate
– Thermal gradients
– WD, energy source
output, feed rate and
• Prediction of microstructure
– Residual stresses
17. Temperature gradient & cooling rate DED
• Each pass creates a track of rapidly solidified material
– Heat input affects the layers underneath.
• Microstructure can be different between layers and within layers
• Microstructure determines the performance of metals
18. Microstructure of a weld - HAZ
● Temperature gradient, G
● Cooling rate / Solidification velocity, R
19. Microstructure of a weld - anisotropic
Like any other AM technology print direction dominates the
microstructure of the material
23. Major Differences b/w EBAM and LBAM
• Electron beams are more efficient at converting electrical energy
into a beam compared to most lasers.
• EBAM is able to produce denser parts with lesser porosity.
For an NiCr based alloy
27. Parameters that affect layer height
Tm - Melting point
To - Interpass Temperature
LH - Layer height
EWW - Effective wall width
α - Thermal Diffusivity
TS - Travel Speed
- Net power into the material
Layer Height WAAM - 1-2 mm
29. Post processing
• The first step is support removal or removal of the part from
• The next and most important step is Heat Treatment.
– to relieve residual stresses - Annealing
– to produce desired microstructure - Ageing or Solution Treatment
• The final step is finishing operations.
30. Post processing
Key Differences b/w Wire Arc/Laser & BD
• Wire Arc/Laser AM are Not Near Net Shape processes.
– Relatively, part shrinkage is a major problem.
– Parts need to be designed larger than required to compensate
• BD processes are Near Net Shape processes.
– May or May not require surface finishing.
31. Size of structures and design constraints
• Ability to produce small scale features. (overall bad for DED)
– Better in Beam Deposition
– Worse in WAAM / WLAM
• Constraint on part size in WAAM / WLAM
– Large scale parts can be realized using WAAM & LBD
– limited in EBAM because of vacuum chamber requirements
32. Wire V/s Powder
• Greater variety and availability of Wire V/s Powder.
• Wire is cheaper than powder.
• Wire is safer than powder and is easier to handle.
• Powder allows for greater resolution and more complex
33. Advantages - summary
• Design freedom
• Composition and Functional gradients are possible.
• In situ alloying
• Large buy-to-fly ratio
• High deposition rate compared to Powder bed deposition (PBD)
34. Challenges - summary
• Post processing required
• Energy intensive
• Powder BD suffer from porous structures, WAAM less so
• Interphase and Interfaces.
• Requires intensive study into process parameters
• Not all powder materials are captured in the melt pool
• Reproducibility of parts.
• Topological optimization and part redesign. (DfAM)
• These technologies, apart from manufacturing, can also be used
for the repair and refurbishing of existing parts.
• Supplemental and possibly an Alternative source of revenue
40. Other Upcoming Metal AM/DED Technologies
1. Cold Spray Additive Manufacturing - application of cold
spraying able to fabricate freestanding parts or to build
features on existing components.
2. SLEDAM - Selective LED-based melting (SLEDM) — the
targeted melting of metal powder using high-power LED
light sources (TU Graz)
3. Hybrid Wire AM where a combination of Arc and Laser
welding is used.
2. Additive manufacturing of metallic materials - Michael Zenou & Lucy Grainger
3. Microstructural Control of Additively Manufactured Metallic Materials - Collins
4. Additive Manufacturing Technologies - Rapid Prototyping to Direct Digital
Manufacturing - Gibson et al.
5. Additive manufacturing of metallic components – Process,structure and
properties - T. DebRoy et al
6. Working distance passive stability in laser directed energy deposition additive
manufacturing - J.C. Haley et al.
7. An investigation on the effect of deposition pattern on the microstructure,
mechanical properties and residual stress of 316L produced by Directed
Energy Deposition - A. Saboori et al.
8. Observations of particle-melt pool impact events in directed energy deposition
- J.C. Haley et al.
1. Titanium Alloys - Ti6Al4V Grade 5. (n.d.). Retrieved May 24, 2020, from
2. Åkerfeldt, P., Antti, M. L., & Pederson, R. (2016). Influence of microstructure on
mechanical properties of laser metal wire-deposited Ti-6Al-4V. Materials
Science and Engineering A, 674, 428–437.
3. Peyre, P., Dal, M., Pouzet, S., & Castelnau, O. (2017). Simplified numerical
model for the laser metal deposition additive manufacturing process. Journal of
Laser Applications, 29(2), 022304. https://doi.org/10.2351/1.4983251
4. Acoff, V. L., Baker, J., Fonseca, D. J., Nastac, L., Weaver, M. L., & Dissertation,
A. (2014). Tuscaloosa , Alabama.
5. Arthur, N. K. K., & Za, N. C. (2019). Laser Based Manufacturing of Ti6Al4V: A
Comparison of LENS and Selective Laser Melting.
6. Wu, B., Pan, Z., Ding, D., Cuiuri, D., Li, H., Xu, J., & Norrish, J. (2018). A review
of the wire arc additive manufacturing of metals: properties, defects and quality
1. Edwards, P., O’Conner, A., & Ramulu, M. (2013). Electron beam additive
manufacturing of titanium components: Properties and performance. Journal of
Manufacturing Science and Engineering, Transactions of the ASME, 135(6).
Notas do Editor
what, where, why, when and how
The term Directed Energy comes from the use some of energy sources, such as a laser, electron beam or plasma arc, focused into a narrow region or beam to melt the feedstock material while it’s being deposited.
And Similar to that of an FDM process, the material is deposited in linewise manner for a particular layer.
Ceramics and Polymers ( Relatively lesser usage)
Most commonly used are Metals, alloys and other metallic derivatives like oxides, in a powder or wire feed form.
A wide variety of Metal DED AM processes can be achieved from the combination of these processes.
We will focus on 3 main processes:
Electron Beam AM
And Beam Deposition – commercially known as Laser Energy Net Shaping or LENS
before we go in to how these two techniques work and their process parameters, we would like you to know where and when you would use these techniques
Any metal that can be welded can be printed with DED
Material can be deposited vertical or non vertical when using an multi axis machine, which allows for potential use in space.
dependent on your CNC work space large components can be manufactured and Material can be deposited on an existing metal block or on a flat build plate.
Adding features to simple shapes to form complex structures which would otherwise have a high “buy to-fly” ratio makes sense.
Moving on to our 1st technology
WAAM is a DED technology and uses an arc welding process to 3D print metal parts.
Wire fed materials as it is standard for welding applications and thus has a wide range of suppliers and properties.
The material deposition technology is similar to that of GMAW or PAW welding,
Depending on the power source available and to some extent the material in use, the arc deposition process is selected.In both cases, inert gas is used in tandem with wire melting to prevent oxidation.
More details about the welding process
The wire, on melting, is extruded in the form of beads on the substrate.
The beads stick together to create a layer of material.
The build plate is set as the anode and the wire as the cathode
The different kinds of defects possible from WAAM are SF, deformation, porosity, residual stresses, delamination, oxidation and cracking.
Titanium and it’s alloys show the best performance out of all the other materials. The high proneness to oxidn results in discoloration as shown on slide 6.
An electron beam is used instead of a laser and Because of the nature of electron beams, a vacuum setup is required in order to be able to accurately control the diameter and flow of electron beams.
It works by using High speed electron streams that bombards the material feed and the Kinetic energy from them, turns into heat upon impact, causing fusion.
No bead creation, direct melting of material.
A heated tungsten filament emits electrons which are collimated and accelerated. They can be focused upto 0.1 mm diameter using a focus magnetic coil. The EB gun is fixed and beam is moved around using a deflection magnetic coil. The layer thickness that determines part resolution is 0.07 - 0.15 mm .
A layer is generated by a number of consecutive overlapping tracks. The amount of track overlap is typically 25% of the track width (which results in re-melting of previously deposited material) and typical layer thicknesses employed are 0.25–0.5 mm.
Typical small molten pool and relatively rapid traverse speed combine to produce very high cooling rates (typically 1,000–5,000C/s) and large thermal gradients. Depending upon the material or alloy being deposited, these high cooling rates can produce unique solidification grain structures and/or nonequilibrium grain structures which are not possible using traditional processing.
Inert gases such as
Ar, N, He.
There is a region above and below the focal plane where the laser energy density is high enough to form a melt pool.
If the substrate surface is either too far above or too far below the focal plane, no melt pool will form.
The powder is melted as it enters the pool and solidifies as the laser beam moves away. Under some conditions, the powder can be melted during flight and arrive at the substrate in a molten state; however, this is normally undesired because the formation and deposition of molten droplets is hard to control. but most importantly these droplets do not always fuse with the substrate and can lead to porosity in the final product.
This process is also similar for WLAM, with the replacement of powder with wire.
WAAM & BD processes microstructure are similar to powder bed fusion processes
, wherein each pass of the laser or heat source creates a track of rapidly solidified material.
High cooling rates and a distinct thermal history lead to features typically found in AM, such as grains elongated in the build direction, dendritic solidification structures and pronounced crystallographic textures
When metals are rapidly molten and solidified the crystal structure goes through a number of phase changes which determine the crystallographic microstructure of the metal.
The biggest determining factor for the performance of metallics is the microstructure.
Therefore the Heating and cooling rates for the layer that is being deposited is fital, are
Pt . 1: which conserves scarce electrical resources; electron beams work effectively in a vacuum but not in the presence of inert gases and are thus are well suited for the space environment.
Laser Beam AM
Variation in Microstructure for the same NiCr (Probably Inconel) based alloy
LBAM gives better properties for strength with temperature , however EBAM gives better fatigue properties, due to lesser porosity. LB has such a scatter pattern due to varying porosities and problems with the reproducibility of the part.
Interpass temperature is the temperature at which subsequent weld runs are deposited.
From the qns above, it can seen that EWW (Effective wall width), due to the squared term, has a strong correlation to heat conduction (Q˙ , Cp, TS) and theHowever, Layer height has a very small effect on heat transfer. Layer heights in WAAM is generally b/w 1 - 2 mm therefore setting limits on the possibilities of Hybrid lattice structures.
The first step is support removal or removal of the part from the substrate.
The next and most important step is Heat Treatment.
to relieve residual stresses - Annealing
to produce desired microstructure - Ageing or Solution Treatment
The final step is finishing operations.
Key Differences b/w Wire Arc/Laser & BD is Wire Arc/Laser are Not Near Net Shape processes and BD processes are Near Net Shape processes
Ability to produce small scale features is overall bad for DED. However b/w the 2 BD is better.
This is due to the need for more dense support structures for complex geometries and the fact that the larger melt pools in DED result in a reduced ability to produce small-scale features, greater surface roughness, and less accuracy.
However on Part size, the only constraint is for the robotic arm to reach the buildplate/ previous layer. WAAM and LBD are meant for Large scale parts.EBAM can’t do so due the limits on vacuum chamber.
Greater variety and availability of Wire V/s Powder.
Wire is cheaper than powder.
Wire is safer Safer, as there is no chance of powder explosion or breathing powder in
Powder allows for greater resolution and more complex structures.
The main adv
The main challenges are:
Problems b/w layer Interfaces and microstructure Interphases
Reproducibility of parts
Topological optimization and part redesign. (DfAM)
These technologies, apart from manufacturing, can also be used for the repair and refurbishing of existing parts.
If this side of the technology is further explored, it will provide a supplemental and possibly an alternative source of revenue for the machine
This a rocket combustion chamber and the nozzle.
An initial substrate is the base of the divergent nozzle made using SS by another process. The isogrid stiffeners and the upper combustion chamber is made solely using LENS (LBD). The finish is sufficient and only the inside of the combustion chamber needs additional finishing.
Part that sits on the back of an F-35 , made by Lockheed Martin
Forging takes 14 months + +4 months for machining and finishing
90% waste of the part material is wasted.
Additionally it is difficult to machine and recycle Titanium and it’s chips
Now a similar part for the Eurofigher Typhoon made by WAAM3D company.
It’s dimensions are (2.5x1.5m)
Can be made in weeks using WAAM
Cost savings come from non recuring tooling costs, No waste of materials in machining and Drastic reduction in lead times
Another WAAM replacement for a commercial aircraft fuselage.
These are some of the newer, upcoming metal AM technologies that we didn’t go deeper into.