1. Directed Energy Deposition (DED)

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
Based System.

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
– Laser
– 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
other techniques.
Adding features to simple
shapes
• Complex structures which
would otherwise have a
high “buy to-fly” ratio.
• “Rib-on-plates”

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
substrate.
• The beads stick together to create a layer of material.
• A robotic arm on a slider is used to deposit material.

10. Defects and their Material Dependencies -
WAAM

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
of material.
• 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
• Layer
– Thickness
0.25 - 0.5 mm
– Width
0.1 - 5 mm

14. How does it work - Laser Powder BD
• Working distance - laser energy density is high enough to form a
melt pool.
• The powder is melted just as it enters the pool not during flight.

15. Proces control DED - Optical feedback
• Measures
– Size and shape weld pool
– Spectrum
– Cooling rate
– Thermal gradients
• Adjust
– WD, energy source
output, feed rate and
travel speed.
• Prediction of microstructure
– Residual stresses

16. WAAM Quality Performance

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

20. Microstructure of powder BD Al 4047
• Interfaces
• Porosity
• Microstructure
gradients in layer

21. Microstructure checkerboard welding
direction

22. Macrosection - WAAM

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

24. Mechanical Property Differences b/w EBAM
and LBAM
For the same NiCr based alloy after post processing

25. Mechanical Properties - Baseline Ti6Al4V
Process UTS [MPa] EL [%]
Cast 860 - 1100 >8
Wrought 930 - 1100 >10
WAAM 900 - 990 6 to 20
WLAM 870 - 930 12 to 22
LENS (LBD) 896 - 1000 1 to 16
EBAM 840 - 860 2.5 to 4

26. Wire Feed Usage Comparisons
Parameters WAAM WLAM EBAM
Wire Usage Efficiency 90% 2 -4% 15-20%
Build Rate 1 - 4 Kg/hr 100 - 300 g/hr 3-9 Kg/hr
Cost of Investment low high high

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

28. Temp. gradient, G Solidification Rate, R
● Pressing map

29. Post processing
• 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.

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
structures.

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
• Cost
• 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.

35. Opportunities
• 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

36. Applications - Space - LENS

37. Applications - Combat Aircraft - Conventional
● Forging 14 months
● +4 months for machining and finishing
● 90% waste
● Difficulty in machining and recycling waste, because Ti

38. Applications - Combat Aircraft - WAAM
● Can be made in weeks using WAAM
● Cost saving upto 70%
● Topology Optimization possibilities

39. Applications - Commercial Aircraft
• Skin Stiffened Fuselage.
• Near Net Shape

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.

41. Questions
Questions?

42. References
1. https://www.3dnatives.com/en/directed-energy-deposition-ded-3d-printing-
guide-100920194/
2. Additive manufacturing of metallic materials - Michael Zenou & Lucy Grainger
3. Microstructural Control of Additively Manufactured Metallic Materials - Collins
et al.
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.

43. References
1. Titanium Alloys - Ti6Al4V Grade 5. (n.d.). Retrieved May 24, 2020, from
https://www.azom.com/article.aspx?ArticleID=1547
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.
https://doi.org/10.1016/j.msea.2016.07.038
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.
https://doi.org/10.4028/www.scientific.net/MSF.950.44
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

44. References
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).
https://doi.org/10.1115/1.4025773