Selective Laser Melting versus Electron Beam Melting

“État actuel des fabrications additives pour les

applications métalliques”

Atelier CNES – 18/19 Novembre 2013, Toulouse, France

Olivier RIGO

Carsten ENGEL

25.11.13 1 © sirris | www.sirris.be | [email protected] |

Special thanks …

Le Fonds Européen de Développement Régional et la Région Wallonne investissent dans votre avenir.


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Sirris | Metal Additive Manufacturing

25.11.13 3

Index

Sirris – short overview

Generalities:

Metal Additive Manufacturing

Technology comparison: LBM vs EBM

Metallurgical aspects

Mechanical aspects

Case studies

Contact

© sirris | www.sirris.be | [email protected] |

Sirris | Driving industry by technology

130 experts & hight-tech infrastructure

Collective centre of the technology industry • Non profit organization • Industry owned

4,700 industrial interventions (advice, projects, services) •within 1,700 different companies •whose 75% are SME’s •24M EUR turnover

Mission: “Increase the competitiveness of companies of the Agoria sectors through technological innovations”

Sirris | 23 years of Additive Manufacturing

AM centre – Leading position in EU 16 engineers and technicians 17 high-tech additive technologies in house Most complete installed base in EU Driving technology companies in applications

Technologies: • Stereolithography (normal & hi-res) • Paste polymerisation for ceramics and metals (Optoform) • 3D Printing of plaster and metal powder • Laser sintering of polymeric powder (PA,…): P360 – P390 • Objet Connex 500: bi-material • Laser sintering of metal powder (parts and mould inserts) • Electron Beam Melting (Arcam A2) • 3D Printing of wax (Thermojet) • Vacuum Casting of Alu, Bronze, Zamak • Laser Cladding (EasyClad) • Laser Beam Melting (MTT) • Bi-material FDM system • Fab@home system (for students) • MCOR technology (color 3Dprinter)



25.11.13 6

Index


Generalities:




Mechanical aspects

Case studies

Contact


Generalities: Metal Additive Manufacturing


Direct

Fabrication

system

Laser

E-Beam

Print head

Nozzle

Post-

processing

Indirect

Binder

Debinding

+ sintering

Post-

processing


Electron Beam

Melting (EBM)

Laser Beam Melting

(LBM)

• Metallic powder deposited in a powder bed • Electron Beam • Vacuum • Build temperature: 680-720°C

• Metallic powder deposited in a powder bed • Laser Beam • Argon flow along Ox direction • Build temperature: 200°C




Electron Beam Melting



Electron Beam Melting

Benefits and drawbacks - EBM

Benefits Drawbacks

Few developed materials, only conductive materials possible

Tricky to work with fine powder

Powder is sintered -> tricky to remove (e.g. interior channels)

Long dead time between 2 productions (8 hours for cooling – A2, A2X, A2XX systems)

Sintered powder = good for thermal conductivity = less supports

Suitable for very massive parts

Less supports are needed for manufacturing of parts

Possibility to stack parts on top of each other (mass production)

Process under vacuum (no gaz contaminations)

High productivity

No residual internal stress (constant 680-720°C build temperature)

Very fine microstructures (Ti6Al4V), very good mechanical and fatigue results (Ti6Al4V)

Expensive maintenance contract



Electron Beam

Melting (EBM)

Laser Beam Melting

(LBM)




25/11/2013 © Sirris | www.sirris.be | [email protected] |

13

Spread powder

Recoater

Laser beam

Melted zones

Previous layers

Initial plate

Argon

Main tank

The building steps


Laser Beam Melting – SLM Solutions 250HL


Benefits and drawbacks - LBM

Benefits Drawbacks

• Flexibility for new material developments

• Possibility to work with fine powders 10µm (d50)

• Easy powder removing from the parts (the parts are not embedded in pre-sintered cake)

• Short dead time between 2 productions (2 hours for cooling)

• Possibility of restarting an interrupted job

• Easy visual inspection of building process during the manufacturing (either with unaided eye or with optical camera)

• Process is wall thickness dependent. (not suitable for massive parts)

• Process involving internal stresses in the parts need additional annealing

• Process requiring strong supports for parts fasten during the manufacturing (not only for heat transfer)

• Need to use build plates of the same material than the powder used in the machine (e.g.: more expensive for titanium powder)

• Cutting tool necessary (eg: a saw) in order to release the parts from the build plate


Technology comparison – EBM – LBM

LBM EBM

Size (mm) 250 x 250 x 350*¹ 210 x 210 x 350*²

Layer thickness (µm) 30 - 60 50

Min wall thickness (mm) 0.2 0.6

Accuracy (mm) +/- 0.1 +/- 0.3

Build rate (cm³/h) 5 - 20 80

Surface roughness (µm) 5 - 15 20 - 30

Geometry limitations Supports needed everywhere (thermal,

anchorage)

Less supports but powder is sintered

Materials Stainless steel, tool steel, titanium, aluminum,…

Only conductive materials (Ti6Al4V, CrCo,…)

CENG 25/11/2013 © sirris 2013 | www.sirris.be | [email protected] | 16

*1 SLM Solutions 250HL *2 Arcam A2

0

2

4

6

8

10

productivity

3D complexity

maximum size

Accuracy Surface finish

mech prop -

density

material range

EBM (Arcam)

LBM (SLM Solutions

Technology comparison – EBM – LBM

CENG 25/11/2013 © sirris 2013 | www.sirris.be | [email protected] | 17

*1 SLM Solutions 250HL *2 Arcam A2


25.11.13 18

Index


Generalities:




Mechanical aspects

Case studies

Contact


Metallurgical aspects – LBM & EBM

Electron Beam

Melting (EBM)

Laser Beam Melting

(LBM)



25/11/2013

© sirris 2013 | www.sirris.be | [email protected] | 19

Experimental procedures

Electron Beam

Melting (EBM)

Laser Beam Melting

(LBM)

• Random scanning strategy • Vacuum • Pre-heating of the subtrate: 680-720°C

• Complex lasing strategy: 79° rotation between two successive layers • Argon flow along Ox direction • Pre-heating of the subtrate: 200°C

Characteristics of theTi6Al4V ELI powders

Process Ti (wt%) Al(wt%) V(wt%)

LBM Bal 5,9 4,2

EBM Bal 3,3 4,4

Reference axis for EBM and LBM


Results and discussion

Laser Beam Melting

Perpendicular to the building direction

• Equiaxed morphology (around 50μm of diameter) • Width does NOT significantly change along the height

No evolution of the thermal gradient intensity, no evolution of the grain

width



Laser Beam Melting

Parallel to the building direction

• Elongated grains characteristic of an epitaxial growth aligned with the heat flow

• No epitaxial growth apparent

Explanation: Tilt of the primary β grains

Suggestion: combined effect of part geometry and a modification of the direction of the maximum heat flow that had possibly been brought about by the Argon flow



Perpendicular to the building direction

• Equiaxed morphology as for LBM

Electron Beam Melting (EBM)

Parallel to the building direction

Explanation: • Random scanning trategy • Thermal homogeneity due to substrate preheating (680-720°C) • No argon flow

Hoped this would allow a significant reduction of internal stresses and then improve mechanical

properties

• Epitaxial growth: • No Tilt (≠LBM)




• Typical morphology of a Widmanstätten microstructure • Pre-heating of the substrate induces slower cooling rates thus favouring a diffusive transformation to α

Cooling rate is directly influenced by the preheating of the substrate: the lower the preheating, the faster the cooling rates and the finer the resulting microstructure

Characteristics:

• Uniform, Fine Grain

• Columnar

• Lamellar Alpha Phase

• Larger Beta Grains




Two types of porosities (spherical and non- spherical) due to entrapped argon in powder particles (amount porosity in GA is about 0.2-0.1%) or un-melted areas can be observed.



25.11.13 26

Index


Generalities:




Mechanical aspects

Case studies

Contact


Mechanichal comparison

Electron Beam

Melting (EBM)

Laser Beam Melting

(LBM)

• Layer Thickness: 70µm • Job 130503a • As built sample without additional post treatment

• Layer Thickness: 50µm • Job 130423a • Laser Beam • Argon flow along Ox direction


Tensile test:

According to standard ASTM E111-04 and

NF EN 10002 standards




Mechanical properties comparison (Tensile testing)

1126

1202

1029

1094

Rp0.2 (Mpa) Rm (Mpa)

Yield strenght/UTS

(Oy samples)

LBM (50µm anealed) EBM (70µm)

3,1

9,9

LBM EBM

A (%)



Mechanical properties comparison (Tensile testing)

1079

1120

974

1032

Rp0.2 (Mpa) Rm (Mpa)

Yield strenght/UTS

(Oz samples)

LBM (50µm anealed) EBM (70µm)

4,1

10,8

LBM EBM

A (%)


Mechanichal comparison

Electron Beam

Melting (EBM)

Laser Beam Melting

(LBM)

• Layer Thickness: 70µm • Job 120124a • As built sample without additional post treatment

• Layer Thickness: 30µm • Job 121214b • Laser Beam • Argon flow along Ox direction



Whöler fatigue curve with a stress ratio of 0.1 and 4 different levels tensile test probes (3 each) : 10-50 kcycles (level 1) 100-200 kcycles (level 2) 500-800 kcycles (level 3) 1-2 exp 6 kcycles (level 4)

Mode: strain-strain Control: force Form: sinusoidal R: 0.1 End process criteria: break or 10^7 cycles


Fatigue test:

According to standard ASTM E466-07


Mechanical properties comparison (Fatigue testing)

EBM Oz Post-machined samples

LBM Oz Post-machined samples



Mechanical properties comparison (Fatigue testing)


LBM Oz Post-machined samples

Ref 2 Roll formed TiAl6V4



Hip treatement in order to improve fatigue properties



EBM Oz Post-machined samples + HIP



Orientation impact?

EBM Ox Post-machined samples + HIP


EBM Oz Post-machined samples + HIP



Surface roughness impact


EBM Oz As-Built sample




25.11.13 38

Index


Generalities:




Mechanical aspects

Case studies

Contact


Case study 01: Massive ESA-CSL part

EBM

Dimensions: 208*175*38mm (L*W*H)

Machining



Case study 02: ESA-CSL-AlmaSpace

LBM Machining

Machining EBW



Case study 03: Design of an “improved”

support geometry for an antenna

Support mass : 223 g 57.5% mass reduction Initial mass ~ 400 g

LBM




25.11.13 42

Index


Generalities:




Mechanical aspects

Case studies

Contact


+32 498 91 94 71

[email protected]

Olivier RIGO

25.11.13 © sirris | www.sirris.be | [email protected] |

Olivier.rigo1

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Selective Laser Melting versus Electron Beam Melting

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Selective Laser Melting versus Electron Beam Melting