1. le centre collectif de l’industrie technologique belge

2. High Value Manufacturing
Density/porosity control of sintered 316L stainless steel
parts shaped by additive manufacturing
15-11-2012
le centre collectif de l’industrie technologique belge

3. Table of contents
• Porous metallic parts
• 3D-printing Prometal process
• Sintering cycle
• Characterization
• Property ranges of 316L powders
• Examples
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4. Porous metallic parts
• Shaping by powder metallurgy  lots of parameters
• Porosity range from a few % to 90%
• Application list:
• Filtration
• Distributing/dispersing/damping
• Airing/cooling
• Lightening
• Catalysts supports
• Prosthesis
• But simple geometries (Pressing, MIM)
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5. Porous metallic parts
• Additive manufacturing  no limit in shape + integrated
functionalities
• SLM  1 step
 no control of porosity
• 3D-printing  indirect route: shaping + sintering
 possibility to control porous characteristics
R10:
1000x500x280mm RXD:
60x40x15mm
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6. 3D- Printing Prometal Process
3. Sintering
Complete
Partial
1. Curing 2. Debinding - presintering
(green part) (brown part) (3’. Infiltration)
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7. Sintering cycle
• From a powder tap to full dense material
• Passing by porous state
• Opened to 92% density, then closed
• Evolution functions of:
• Initial state
• Packing density
• Particle size distribution
• Particle shape
• Sintering conditions
• Temperature
• Time
• (Atmosphere)
•  Stop at different stage to keep or eliminate porosity following
target application
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8. Characterization
• Density – porosity (opened and closed)  Archimedes (3 weightings)
• Permeability k  Darcy (flux Q through thickness L and surface A under DP)
Q.L.µ
k=
A.∆P
• Pore size (bubble point and Hg porosimetry)  Washburn
− 4.γ . cos θ
d=
P
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9. Property ranges for 316L powders
100 40
22µm
• Effect of sintering T° 95 31µm
20-53µm
35
(90min at T°) for 4
45-90µm
90 30
Opened porosity (%)
Relative density (%)
spherical powders 85 25
80 20
75 15
70 10
65 5
60 0
1180 1200 1220 1240 1260 1280 1300 1320 1340 1360 1380 1400 1420 1440
Temperature (°C)
0,9
Porous part Dense part 0,89
0,88 1315°
• Effect of sintering time 0,87 C
Density (-)
0,86 1335°
at 3 T° for 31µm 0,85
C
1345°
powder 0,84
0,83
C
0,82
0,81
0 50 100 150 200 250 300 350
Time at sintering temperature (min.) 9

10. Property ranges for 316L powders
35 1,00E-12 • Pore size and permeability
22µm
functions of opened
porosity for 4 spherical
31µm
30
20-53µm
powders
Mean pore size (µm)
45-90µm 1,00E-13
25
Permeability (m²)
20
1,00E-14
15 • Link between parameters:
• Powder size sets pore size
10
1,00E-15 • Thermal cycle sets final
density/porosity
5
•  all defines permeability
0 1,00E-16
Main challenge: shrinkage
0 5 10 15 20 25 30 35 40
•
control!
Opened porosity (%)
Pore mean size
Permeability 10

11. Property ranges for 316L powders
45-90µm powder
Gas atomised particles Water atomised particles
Sintered 90min at 1395°C
65% density – 35% opened porosity 47% density – 53% opened porosity
Mean pore size 35µm Mean pore size 30µm
Permeability 10-12m² Permeability 10-12m²
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12. Examples
Ø 70mm
Pores 30µm
Perméa. 10-12 m²
L 270mm
Ø 50mm Pores 17µm
Pores 30µm Perméa. 5.10-13 m²
L 30mm
Perméa. 10-12 m²
Ø 300mm
L 90mm
Pores 35µm
Pores 35µm
Perméa. 10-12 m²
Perméa. 10-12 m² 12

13. Thank you for your attention !
Bruno.Verlee@sirris.be
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