Lecture 6 - DIRECTED ENERGY DEPOSITION

Question 1

Describe Direct energy deposition

Answer 1

Focused thermal energy is used to fuse

materials by melting as the material is being deposited.

Question 2

list the 3 energy sources for this process

Answer 2

Laser
Electron beam
Plasma arc

Question 3

Laser beams pros cons

Answer 3

pros
- Highly intense
– Highly directiaonal
– Cheaper and more flexible
– Does not require a vacuum environment

cons
– Inert atmosphere required

Question 4

Electron beam Pros/cons

Answer 4

– Fast deposition rates
– Very interesting to space-based applications
• Electron beams are much more efficient at converting
electrical energy into a beam which conserves scarce
resourses.
• Work well in a vacuum
• Powder inherently difficult to use in a zero gravity environment
so wire feed used

Question 5

Plasma beam

Answer 5

Has been used in combination with milling to produce 3D structures.
– Larger heat-affected-zone and process control issues have kept this
approach from widespread commercialization

Question 6

LENS process - draw pic

Answer 6

See notes

Question 7

LENS- Descirbe

Answer 7

Deposits are typically made in
a controlled argon atmosphere (no oxygen)

• Sheath gas compresses
powder stream

Question 8

EBAM- Draw pic

Answer 8

SEE NOTES

Question 9

EBAM - describe

Answer 9

• Electron beam to create melt pool
• Requires a vacuum environment
• Wire fed

Question 10

List 2 feedstocks and describe

Answer 10

Powder
Most versatile feedstock
– Most metals and ceramics are available in powder form
– Not all powder is captured in the melt pool (i.e. less than 100% powder
capture efficiency)

Wire fed
– 100% capture efficiency
– Higher porosity
– Harder to achieve 3D geometry
– Cheaper than powder for identical material

Question 11

Single nozzle vs 4 nozzle

Answer 11

Single nozzle system
– Cheaper to produce
– Slower deposition rate

4 nozzle system
– 90° separation
– Faster deposition rates
– Wider range of alloys

Question 12

LENS describe Mechanical properties/micro structure controll

Answer 12

small melt pool cools fast leading to fine grains similar to wrought products

Can controll microstructre by changing print parameters.

Question 13

Pros of LENS (Laser-Engineered-Net-Shaping)

Answer 13

pros
Fine microstructure results in high hardness equivalent to wrought parts

diverse control of microstructure

Very high density parts

Functionally graded metals

Good “buy-to-fly” ratio as not alot of high performance alloy is wasted

Faster deposition rates than Powder Bed Fusion

Question 14

Cons of LENS (Laser-Engineered-Net-Shaping)

Answer 14

Cons

X Requires an inert atmosphere or vacuum environment

X Poor resolution and surface roughness

X Cannot produce as complex structures as say powder bed process

Question 15

Applications of LENS

Answer 15

Part production
Repair
Adding new features too existing parts

Question 16

(tutorial) Which 4 ASTM F42 process categories can generate metallic parts?

Answer 16

Sheet lamination

Binder jetting

Directed Energy Deposition

Powder Bed Fusion

Question 17

Tutorial
2. Provide one process example of the ASTM F42 direct energy
deposition process category and describe that process. The example
should include a description and diagram to explain the process.

Answer 17

Lecture notes

Question 18

Explain the advantages of the 2 feed stock materials

Answer 18

Previous question

Question 19

4 reasons why direct energy deposition is attractive for the areospace industry

Answer 19

Good buy to fly ratio-often expensive alloys are used to make parts and this utilises them at a high efficiency -cost saving

large range of metals that can be deposited such as titanium alloys-versatile

Very strong parts due to micro structure from small melt pool-stonger = less material used

Functionally graded materials are possible, therfore could potentially reduce weight of parts

Question 20

(Exam)
With the aid of a diagram describe a Direct Energy Deposition
process.

Answer 20

LENS

Laser Engineered Net Shaping (LENS)

• In the LENS process an infrared laser is focused through a nozzle onto the
work part.
• Metal powder is fed into the focal point of the laser where it is melted and
deposited onto the work part.
• A sheath gas is used to ensure the melting reaction takes place without
oxidising the powder and to ensure the powder does not ignite. This also
gives good wetting of the melted material to the underlying layers
• The deposition head then moves to deposit the next layer
Or

Electron Beam Additive Manufacturing (EBAM)
see notes