Renishaw Ti6Al4V metal powder re-use study
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Transcript of Renishaw Ti6Al4V metal powder re-use study
Investigating the effects of multiple powder re-use cycles in
AM
Lucy GraingerProduct Marketing Engineer, Renishaw
Why even investigate powder re-use in AM?
• Feedstock should be reliable for process repeatability and predictability
• Powder properties and machine parameters are closely related
• Reduce potential waste
Why even investigate powder re-use in AM?
Why is titanium so special?
Why titanium?
Ti-6Al-4V alloy
High strength to weight ratio
High corrosion resistance
45 % lighter than steel $$$$$
Why use additive manufacturing?
Subt
ract
ive
Addi
tive
Billet CNC machining Component + waste – high buy-to-fly
Powder Powder bed fusion Near net shape + little waste – low buy-to-fly
What steps contribute to a re-use cycle?
Re-use cycle
Metal powder bed fusionRoutine build + test samples
Remove build plate
Sieving Remaining
un-melted powderRe-use
Return sieved powder to silo
repeat
AM250 system
AM250
Max build volume 250 mm x 250 mm x 300 mmBuild rate* 5 cm³ to 20 cm³ per hour
Layer thickness 20 to 100 µm
Laser beam diameter 70 µm at powder surface
Laser options 200 W
Power supply 230 V 1PH 16 A
Power consumption 1.6 kWh
Gas consumption < 30 l/hr* Build rate is dependent on material, density & geometry, not all materials build at the highest build rate.
Minimising possible contamination
Renishaw AM machines are unique in the way the inert atmosphere in the build chamber is created.
1. A vacuum is created, 35-50mbar:
• This removes air and any humidity from the entire system
2. The chamber is filled with ~600 litre of high purity argon.
3. The atmosphere is maintained at below 1000ppm (0.1%) oxygen and can be set to run below 100ppm (0.01%) for titanium (Ti6Al4v) and other alloys.
Key Benefit: Gas consumption is typically <30 L/hr and laser melting commences approx. 10 minutes after the process cycle starts.
All Renishaw systems are suitable for building reactive materials.
Both chemistry and physical properties of the powder are essential to the quality of the
end product!
Powder chemistry – Titanium alloy grades
Element%
Ti6Al4V Grade 5 Ti4Al4V (ELI)
Oxygen 0.20 0.13
Nitrogen 0.05 0.05*
Carbon 0.08 0.08
Hydrogen 0.0125 0.0125
Aluminium 5.5-6.75 5.5-6.50
Vanadium 3.5-4.5 3.5-4.5
Interstitial
Alloying
*Some grades quote 0.03% max
Physical characteristics of powder
Flow
PSD – Particle size distributionShape/morphology
Density/Packing
Flowability is important for consistent layers, it is directly influenced by PSD, packing and particle shape.
x
Test samples for analysis
Tensile test bars:3 x as built3 x as machined
Density block
Powder capsule60 g of powder approximately
Results - Chemistry
Chemistry - Oxygen
0
500
1000
1500
2000
0 5 10 15 20 25 30 35 40
Oxy
gen
/ ppm
No. of builds
1300 ppm Ti6Al4V ELI max.
2000 ppm Ti6Al4V grade 5 max.
• Initial study over 20 builds• Second study over 38 builds
Chemistry - Nitrogen
0
100
200
300
400
500
0 5 10 15 20 25 30 35 40
Nitr
ogen
/ pp
m
No. of builds
N ppm max
N ppm alternative max
• Initial study over 20 builds• Second study over 38 builds
Experimental results - Physical
Powder morphology
Virgin powder Build number 3Virgin powder
Powder morphology
Virgin powder Build no. 18 Build no. 38
Powder morphology
Build number 38
Particle size distribution and flow
Vol
ume
dens
ity /
%
Size Classes / µm
Little change in particle size distribution over 38 builds
Particle size distribution and flow
0.00
10.00
20.00
30.00
40.00
50.00
60.00
0 5 10 15 20 25 30 35 40
Part
icle
siz
e / µ
m
No. of builds
D90
D50
D10
Particle size distribution and flow
0.00
10.00
20.00
30.00
40.00
50.00
60.00
0 5 10 15 20 25 30 35 40
Part
icle
siz
e / µ
m
No. of builds
D90
D50
D10
Agglomerate
Small particle sintered to larger particle
Particle size distribution and flow
0
5
10
15
20
25
30
35
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 5 10 15 20 25 30 35 40
Flow
/sg-
1
D50
/µm
Builds
Flow
D50
Tensile properties
600
700
800
900
1000
1100
1200
0 5 10 15 20 25 30 35 40
UTS
/ MP
a
Build
Machined
As built
• Density – previous study showed consistently dense components
• Fractography of tensile test bars
• Repeat but over normal running conditions with new powder additions
Further work
• Re-use doesn’t seem to affect the AM process
• General but not significant changes to the powder both chemically and physically
• This is an extreme look at how powder is affected by being used in an AM process, regular topping up of the silo with virgin powder will most likely dampen the effect of the chemical and physical changed to the powder
• There doesn’t seem to be any requirement to dispose of powder - this obviously depends on the requirements of the component.
Conclusions
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