1. Selective Laser Melting of Net-Shaped Oxide Ceramics
State of the Art in Selective Laser Melting of
Alumina Zirconia Ceramics
June 2012
Yves Hagedorn

2. Outline
Introduction
Process Development
Properties of Manufactured Parts
Cost Drivers
Conclusion

3. Introduction SLM of Net-shaped Ceramics
Competences Rapid Manufacturing Department
Process Development
 Qualifying Selective Laser Melting (SLM)
for enlarging the scope of applicable
materials
 Improving component’s quality
 Increasing productivity
 Developing systems and components
Application Development
 Qualifying Selective Laser Melting (SLM)
for series Production
Tooling
Dental applications
Medical implants
Turbo machinery
Mechanical engineering
3

4. Introduction SLM of Net-shaped Ceramics
Selective Laser Melting (SLM) for Ceramics
Principle
3D-CAD Model
in slices
Complex, net-
shaped part in
series material
Powder material
4

5. Introduction SLM of Net-shaped Ceramics
SLM Readily Applied in Industry
Some Industrial Applications
for Metals
Tooling Spacecrafts Medical
© GFE Inno-Shape
Undercuts Complexity Individuality
 Internal structures  Filigree structures  Tool-less production
as cooling channels without joining of customized parts
6

6. Introduction SLM of Net-shaped Ceramics
SLM for Ceramics
Advancements in SLM Allow for
Fabrication of 3D Ceramics
Positive Material SLM Industrial
Properties Manufact. Process Application
+ Mechanical Strength + Tool - Free Medical Applications
+ Wear Resistance + Complex Geometries  Dental Restorations
+ Thermal Resistance + Fast  Implants
+ Bio-Compatible + High Material Yield
+ Esthetics + Cost Efficient High-Tech Applications
 Aerospace
 Automotive
7

7. Introduction SLM of Net-shaped Ceramics
Selective Laser Melting (SLM) for Ceramics
Main Objective
 Development of SLM process for ceramics
Current Application
 Framework for dental restorations from
alumina / zirconia compounds
Exploitation of high material strength
Improved esthetics compared to Cr/Co
® BEGO Medical 2002 8

8. Outline
Introduction
Process Development
Properties of Manufactured Parts
Cost Drivers
Conclusion

9. Process Development SLM of Net-shaped Ceramics
The System Al2O3 / ZrO2
Eutectic System
 Utilization of eutectic powder ratio
Simultaneous crystallization of
alumina / zirconia crystals
Fine-grained microstructure
S. M. Lakiza and L. M. Lopato. J.Am.Ceram.Soc.80 (1997), 893- 902
10

10. Process Development SLM of Net-shaped Ceramics
SLM for Ceramics
Approach
 Complete melting of ceramic material
High densities
High strength
11

11. Process Development SLM of Net-shaped Ceramics
SLM for Ceramics
First results
 High density
 Micro-cracks throughout material
High thermal gradients during
selective melting
Low strength of manufactured
objects (10 MPa)
12

12. Process Development SLM of Net-shaped Ceramics
SLM for Ceramics
Experimental Setup I/II Homogenisation Scanner
optics
 CO2 laser-preheating
Nd:YAG-laser
Focussing optics
Pyrometer
Decrease of thermal gradients
during selective laser melting CO2 -laser beam Powder distribution
(preheating)
Heat Powder reservoir
isolation
Substrate
Crack-free specimens SLM part Building
plattform
13

13. Process Development SLM of Net-shaped Ceramics
SLM for Ceramics
Experimental Setup II/II
14

14. Process Development SLM of Net-shaped Ceramics
Experimental Conduction
Thermal Image
 High-Temperature preheating
Preheating temperature
~ 1800°C
Homogenous temperature
distribution
15

15. Process Development SLM of Net-shaped Ceramics
Experimental Challenges
 High Density
1 > 99 %
 Crack free specimens
2 High-temperature pre-heating
 High Mechanical Strength
3 > 500 MPa (DIN Norm for dental restorations)
 High Surface Quality
4 Rz < 100 µm (own specification)
16

16. Outline
Introduction
Process Development
Properties of Manufactured Parts
Cost drivers
Conclusion

17. Properties of Manufactured Parts SLM of Net-shaped Ceramics
Density & Powder
Spherical Powder
 Excellent flowing ability
Full density
No crack formation
1 mm
18

18. Properties of Manufactured Parts SLM of Net-shaped Ceramics
Microstructure
SEM Image
 Al2O3 matrix (dark)
 Dendritic structure of ZrO2
crystals (bright)
 Tunable fine-grained
microstructure
Complete melting of ceramic material
19

19. Properties of Manufactured Parts SLM of Net-shaped Ceramics
High-temperature Creep Creep of Alumina / Zirconia Material
Sintered vs. SLM 30,00%
 Loading with 200 g 25,00%
SLM
20,00%
 Eutectic material ratio
Elongation
15,00%
 Max. elongation ~ 24% 10,00%
Sintered
5,00%
0,00%
1600°C/2h 1650°C/2h 1650°C/4h 1700°C/2h 1700°C/4h
Temperature/time
This Analysis has been performed by Innalox bv, Netherlands
SLM material shows decreased creep compared to sintered material
20

20. Properties of Manufactured Parts SLM of Net-shaped Ceramics
XRD Analysis
Crystallographic distribution
 Tetragonal ZrO2 crystals
 Phase shift ZrO2:
tetragonal  monoclinic
This Analysis has been performed by TNO Science and
Industry, Netherlands
Self healing abilities of ZrO2 persist despite complete melting
21

21. Properties of Manufactured Parts SLM of Net-shaped Ceramics
Mechanical Strength
Test Samples
 Eutectic material ratio
 Dimensions: ø 18 mm x 2.5 mm
 Flexural strength > 500 MPa
 Flexural strength of sintered
material > 1000 MPa
Load
Specimen
Support
Mechanical strength sufficient for r = 5 mm
dental restorations (DIN Norm) 22

22. Properties of Manufactured Parts SLM of Net-shaped Ceramics
Mechanical Strength
Conventionally 10 mm SLM 10 mm
Max. load 2299 N Max. load 1435 N
Material: ZrO2 Material: Al2O3/ZrO2
Rz value: ~ 10 µm Rz value: ~ 100 µm
Minimum load for application  1000 N
Sufficient strength for application despite weaker material and poor
surface quality 23

23. Properties of Manufactured Parts SLM of Net-shaped Ceramics
Surface Quality
Dimensional Accuracy
 Milled part ~ 50 µm
 SLM part ~ 150 µm
5 mm
Accuracy not sufficient for fitting
24

24. Properties of Manufactured Parts SLM of Net-shaped Ceramics
Surface Quality
Scanning Strategy
Hatch
 Large melt pool due to high
temp. preheating
 Contour / hatch Contour
 Impact on surface quality Contour
Contour parameters spacing
Contour spacing
Improved surface quality due to small melt pool size at contour
25

25. Properties of Manufactured Parts SLM of Net-shaped Ceramics
Surface Quality
Contour Parameters I/II
Rz ~ 112 µm 2 mm
Sa ~ 54 µm
Laser output: 150 W
Scanning speed: 250 mm/s
26

26. Properties of Manufactured Parts SLM of Net-shaped Ceramics
Surface Quality
Contour Parameters II/II
Rz ~ 60 µm 2 mm
Sa ~ 14 µm
Laser output: 40 W
Scanning speed: 120 mm/s
Surface quality strongly depends on geometry
27

27. Properties of Manufactured Parts SLM of Net-shaped Ceramics
Demonstration Object
Improved Surface Quality
 Surface roughness Rz < 100 µm
 Further improvements foreseen
(Rz < 50 µm)
10 mm
Employment of SLM for ceramic dental restorations
possible
New challenging applications needed
28

28. Outline
Introduction
Process Development
Properties of Manufactured Parts
Cost Drivers
Conclusion

29. SLM of Net-shaped Ceramics
Cost drivers SLM Ceramics
Assumptions
50
Milled part ~ 30 € Powder (200 €/kg)
Cost of dental restoration in €
40
Electricity (20 kWh)
30
Depreciation (5 years)
20
Manufacturing time (20 h/50 parts)
10
SLM part 22 € Personnel costs (25 Euro/h)
0
-100 -50 0 50 100 150 200 Total investment (450 000 Euro)
Relative change in %
SLM is competitive compared to milled dental restorations
30

30. Outline
Introduction
Process Development
Properties of Manufactured Parts
Cost Drivers
Conclusion

31. SLM of Net-shaped Ceramics
Conclusion
 First Bridges Produced
1 Sufficient strength, fitting subject to improvements
 Great Environmental Gain
2 20 crowns  50 g material
 Great Economical Gain
3 Forming & densification  1 process step
 Possible new Applications
4 Increased thermal stability
32

32. SLM of Net-shaped Ceramics
Thank you for your attention!
The research was partly funded by the
European 6th framework project „Custom
IMD“
Thanks to our project partners!
Dipl.-Ing. Dipl.-Wirt.-Ing. Yves Hagedorn M.Sc.
Tel.: +49-(0)241-8906-674
Fax: +49-(0)241-8906-121
Hagedorn@ilt.fraunhofer.de
www.ilt.fraunhofer.de
33