free electron laser nitriding of metals - aps physics electron laser nitriding of metals: from basic...

16. Juni 2006

University of Göttingen

University of Göttingen, 2nd Institute of Physics© Peter Schaaf - www.schaaf.physik.uni-goettingen.de 1

Free electron laser Free electron laser nitridingnitriding of metals:of metals:from basic physics to industrial applicationsfrom basic physics to industrial applications

Peter SchaafPeter Schaaf a)a), M. , M. ShinnShinn b)b), E. , E. CarpeneCarpene a)a), J. Kaspar, J. Kaspar c)c)

Zweites Physikalisches InstitutZweites Physikalisches Institut

APS April Meeting 2006, Dallas,TX

Thin Film or FunctionalCoating: made fast

Substrate, work piece

Reactive ornon-reactiveatmosphereN2

Laser Nitriding

a)

b)

c)

University of Göttingen, 2nd Institute of Physics2© Peter Schaaf - www.schaaf.physik.uni-goettingen.de16. Juni 2006

Applications of Thin Films and Coatings


Preparation/Modification of Thin Films and Coatings

Laser Synthesis of Thin Films and Coatings (Nitriding, Carburizing, Hydriding): experimental principles, interactions, melt, plasma, dynamics, diffusion, solidification, …

Fe-N and Fe-C, Austenitic stainless steelTiN and TiCAlN and AlCSi3N4 and SiC (IBM-Milliped)Laser-Conditioning of MagnesiumLaser-Hydriding Ti-HProduction pc-a:Si(H) (TFT)β-FeSi2 (photovoltaics, optoelectr.)Fe/Ag Multilayers by PLD (GMR, TMR) Polymer-PLD (Applications)Epitaxial recrystallisation (SiC, SiO2)

Excimer LaserExcimer Laser 55 ns55 nsNd:YAG LaserNd:YAG Laser 8 ns8 nsFELFEL 1 1 pspsTi:SapphireTi:Sapphire 150 150 fsfs


Laser Synthesis: temperature, plasma

0 100 200 300 400 500300

1000

2000

3000

4000

5000

6000

7000

Tb

2 J/cm²

2.5 J/cm²

3 J/cm²

6 J/cm²

8 J/cm²

laser pulse

4 J/cm²

Tkrit.

Tm

surfa

ce te

mpe

ratu

re T

s [K

]

time t [ns]

105 10 K/sdTdt

= − ⋅

0 100 200 300 400 5000

200

400

600

800 8 J/cm²6 J/cm²

3 J/cm²

2.5 J/cm²

2 J/cm²

4 J/cm²

mel

ting

dept

h d liq

(t) [n

m]

time t [ns]

liq 5.25m/sd d

dt= −

Fe

plasmaplasma--formationformation

evaporationevaporationablationablation

Excimer Laser: Excimer Laser: λλ=308 nm (4.03 =308 nm (4.03 eVeV))ttpp=55 ns (FWHM), 5x5 mm=55 ns (FWHM), 5x5 mm²²,,H=4 J/cmH=4 J/cm²² (I(I00=70 MW/cm=70 MW/cm²²))

vacuum: vacuum: PLDPLD

but: ambient atmosphere at high pressure prevents ablation, causes high pressures, chemical reactions,take-up into liquid surface, re-solidification, coating forms

FeFe

Laser

Numerical: FDM, incl. evaporation, Knudsen

gas transparent for laser

1-10 bar N2


Fe, 9 bar9 bar N2, 4 J/cm²

surfacesurface

Process: Principle of Laser Synthesis



ImportantImportant: melt pool and plasma dynamics: melt pool and plasma dynamicsPlasma: expansion, but gas pressure, Plasma: expansion, but gas pressure, Laser Laser ⇒⇒ Laser Absorption Waves (LSAW)Laser Absorption Waves (LSAW)LSC LSC –– Laser Supported Combustion WaveLaser Supported Combustion WaveLSD LSD –– Laser Supported Detonation WaveLaser Supported Detonation Wave

Plasma (600 ns) :Laser pulse: 55 ns

surfacesurface

10

20

40

60

150

350

600

10m

m

Hom. Beam0.1 MPa 0.9 MPa

ns600 ( )

3112

0

02⎥⎦

⎤⎢⎣

⎡⋅−=ρ

γ IvLSDw

LSD-modelincreased gas pressureincreased gas pressure ⇒⇒ plasma expansion more slowly –Plasma pressure higher and lasts longer!pp: 1 bar : 500 bar – 9 bar : 1050 bar

surfacesurface1 bar : vLSD = 9.7(16) km/s9 bar : vLSD = 6.6(16) km/s

1 bar : vLSD = 10.4 km/s9 bar : vLSD = 5.0 km/s

Theory Experiment

0 20 40 60 80 1000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

v

9 bar N2

1 bar N2

pulse duration

9 bar N2

1 bar N2

raw beam

hom. beamplas

ma

front

pos

ition

zfro

nt [

mm

]

time t [ns]


TiN

•Irradiation of Ti in N2•Free-Electron Laser FEL


Overview: TiN coatings

FEL2:Ti-37 22 18

Ti:Sapphire+CPA750 nm150 fs

Excimer Laser308 nm55 ns

Nd:YAG1064 nm, 532 nm6 ns

FEL3100 nm, 1050 nm< 1 ps


Faster and better with FEL ?

Time ( s )

Time ( µs )

Time ( ps )

Micropulse

Macropulse

1 ps

16 ms250 µs

27 ns37.4 MHz

FELNewport News,Virginia, USA

3.1 µm2 kW

flexible in timing

upgrade: 10 kW, UV (300 nm), 2005

F2-Ti-23

10 mm


FEL: TiN Synthesis

b

a

100 µm

bSample

Macrotm (µs)

Macrofm (Hz)

shiftδ (µm)

Fluenceφm (J/cm2)

Ti-a1 250 60 200 123

Ti-a2 250 60 100 123

Ti-a3 250 60 50 123

Ti-b1 500 30 100 246

Ti-c1 750 30 100 369

Ti-d1 1000 10 200 492

Ti-d2 1000 10 100 492

Ti-d3 1000 20 200 492

Ti-d4 1000 30 200 492

Ti-d5 1000 30 100 492

Line scan: velocity u=0.5 mm/s, line width D=0.4 mm, shift δ (50, 100, 200 µm)

formation of TiNconcentration gradientindependent of parametersstructure of surface?D

v

0 100 200 300 4000

10

20

30

40

50

60

Ti-a2: 250 µs/60 Hz Ti-d2: 1000 µs/10 Hz Ti-d3: 1000 µs/20 Hz

FEL - Ti in 1 bar N2

nitro

gen

conc

entra

tion

[at.%

]

depth [nm]

Always TiN


FEL TiN: Surface by SEM

50 µm 50 µma2: 250 µs, 60 Hz, 100µm c1: 750 µs, 30 Hz, 100µm

50 µm 50 µmd5: 1000 µs, 30 Hz, 100 µm d1: 1000 µs, 10 Hz, 200µm


Ti18: 250µs, 60Hz, 100µm: No Texture

JJöörg Kaspar, IWS Dresdenrg Kaspar, IWS Dresden

EDX

~ 23 at.% N

~ 16 at.% N

~ 8 at.% N

Surface very rough, melting pearls, network of fine cracks, melting depth 30-40 µm, TiN 5-15 µm, primary solidification of TiN at the surface, TiN has a nitrogen rich kerneland less nitrogen cover, α‘-Martensite in between


Ti23: 1000µs, 10 Hz, 200µm, (100) Texture

JJöörg Kaspar, IWS Dresdenrg Kaspar, IWS Dresden

EDX: ~30 at% N

EDX: ~10 at% N

melting zone 20-30µm, TiN 0-25µm, Very smooth surfaces, very few melt pearls, significant solidificationlines, fine cracks.cracks only within TiN. TiN cover smaller.TiN perpendicular to the surfaces, dendritic solidification


GIXRD: Texture, Rocking curves

30 40 50 60 70 80 90 100

100

1000

10000

100000

5 10 15 20 25 30 35 400

10000

20000

30000

40000

50000

α-Ti(N)(102)

TiN(220) TiN(311)

α-Ti(N)(101)

TiN(111)

TiN(400)

TiN(200)

Log(

Inte

nsity

)

2 theta

Ti-a2 Ti-d1 Ti-d5

inte

nsity

theta

1000 µs, 10 Hz, 200 µm

1000 µs, 30 Hz, 100 µm

250 µs, 60 Hz, 100µm

Strong texture for long macropulsesand small overlap

no texture for short macropulses and large overlap

TiN(200)

10 100 6001E-3

0.01

0.1

0.721

0 = perfect (200) texture

perfect polycrystal = no texture

text

ure

para

met

er η

overlap σ0,0 0,5 1,0 1,5 2,0

0

2

4

6

8

10

12

Har

dnes

s [G

Pa]

depth [µm]

Ti-d1 Ti-d2 Ti-d3 Ti-d4 Ti-d5

Rocking curve

hardness

no texture (polycryst.)

δσ

⋅⋅

=v

fD2

fully textured (single cryst.)


FEL TiN: Pole Figures

Symmetric -> columnar growth, fiber texturevery strong texture, well aligned columns

0

100

200

300

400

500

600

0

30

60

90

120

150

180

210

240

270

300

330

0

100

200

300

400

500

60070 72 74 76 78

0

100

200

300

400

500

600

TiN

(311

) pea

k in

tens

ity

Ti-d1 Ti-d5

TiNx(311) Bragg peak (asymmetric scan: γ=25.24°)

Inte

nsity

2 theta

Ti-d3 (Ti-25)

scan: 5° × 5°

ϕ: 0-360°

χ: 0-80°


Simulation of Melting and Solidification

0

1000

2000

3000

40000 200 400 600 800 1000 1200 1400

0 200 400 600 800 100012001400

50

40

30

20

10

0 0 20 40 600,00,20,40,60,81,0

surfa

ce te

mpe

ratu

re [K

]m

eltin

g de

pth

[µm

]

time [µs]

Ti-N

tmacro=750 µs

N fr

actio

n

depth [µm]

TiNx

Strong dependence of the melting temperature on the nitrogen content

nitrogen concentration gradient:

re-solidification starts at surface

free (200) surface is most favorable


Comparison: Simulation and cross section

0 250 500 750 1000 1250 150060

50

40

30

20

10

0

mel

ting

dept

h [µ

m]

time [µs]

10 µm

SEM

E. Carpene, PS, MRS Proc. 780 (2003) Y5.8.1E. Carpene, M. Shinn, PS, Appl.Phys. A (2005)


FEM - Simulations

melting depth:TiTiN

diffusion depth (1/e):1 Pulse2 Pulses2 Pulses(corr.)

Phase diagramme:

Tm = f(N%)

23% solubility0,0 0,5 1,0 1,5 2,0 2,5 3,0

100

80

60

40

20

0

dept

h [µ

m]

time [ms]

pulse duration

vS= 2-3 cm/s

0,0 0,5 1,0 1,5 2,0100

80

60

40

20

0vS= 1,5-2,5 cm/s

dept

h [µ

m]

time [ms]

pulse duration

0 100 200 300 400 500100

80

60

40

20

0

dept

h [µ

m]

time [µs]

pulse duration

1,0 1,1 1,2 1,3 1,412

8

4

0

dept

h [µ

m]

time [ms]


TiN: hardness – comparison laser

Femtoseconds – verysoft (nanocluster)

FEL highest hardnessand thickest coating

Ti

Excimer = „smooth“ (Ra < 0.5 µm)Nd:YAG: Ra ~ 1-2 µmFEL: smooth (cracks)

0.01 0.1 1 100

2

4

6

8

10

Nd:YAG

Excimer Laser

FEL

Untreated Titanium Femtosecond Pulses

Har

dnes

s HU

1 [G

Pa]

Depth [µm]


FEL TiN: Surface by SEM

50 µm 50 µm

veryvery promisingpromising forfor

implantimplant surfacesurface structuringstructuringa2: 250 µs, 60 Hz, 100µm c1: 750 µs, 30 Hz, 100µm

Kieswetter K, Schwartz Z, Hummert TW, Cochran DL, Simpson J, Dean DD, Boyan BD.

Surface roughness modulates the local production of growth factors and cytokines by osteoblast-like MG-63 cells. Journal of Biomedical Material Research 1996; 32 (1): 55-63.

50 µm50 µm

d5: 1000 µs, 30 Hz, 100 µm d1: 1000 µs, 10 Hz, 200µm


Real Human Implant (hip joint)3D image of a laserstrcutured hio joint (drillingholes of D=200 µm)

Aim: durable osseo-integration and implant stability

Way: Surface must be a good stimulus for boneingrowth (good microcontacts=osseo-integration) very stable bone-implant-connection

chemical modification for chemical resistivity

Laser-Structuringof an hip-joint


Femtosecond pulses (Ti:sapphire laser)

nitrogengas (N2)

150 150 fsfslaserlaserpulsepulse

plasmatp=1.5·10-13 s (pulse duration):⇒ non-thermal treatment

(Coulomb explosion)

• affected depth ~ 10 nm• plasma only after laser pulse• highly ionized vapor

TiTi--sapphire, 780sapphire, 780--850 nm850 nm150 150 fsfs, 1.5 bar N, 1.5 bar N22

tp<< te ⇒ Telec >> Tlatt

Ti:Saphir mit CPA, tTi:Saphir mit CPA, tpp=150 =150 fsfs, , λλ=800 nm=800 nm


Applications: Cylinder Liners

J. Lindner, AUDI AG


In series production: V6 engine

Treatment: mirror inside cylinder; rotating engine block, in series production, 5 Excimer simultaneous, 2 min/engine

J. Lindner, AUDI AG


Application: Cylinder liners (grey cast iron)

After honing

After laser treatmentReduction of oil consumption (30x)increase in efficiency and power


Application: Cam Shafts


FEL: from basic to applied physics


Summary

Reactive Laser treatments enable flexible, clean and fast ways for the production of new materials, thin films and coatingsEasy and fast modification and functionalizing of thin films andcoatings by laser beams.But: sensitive adaptation of material, laser, and laser treatment for the specific application.Combination of several methods for resolving complicated processes and optimization of processing necessary.FEL is very attractive for fast (competitive) surface treatmentsNanostructuring, Pulse tailoringMany Perspectives for thin films


CooperationsFEL, Jefferson Lab, Newport News, Virginia, USAAUDI AG, Daimler Benz, INA Wälzlager, IBM, StihlProf. H.-W. Bergmann (†), Uni Bayreuth, Metall. WerkstoffeProf. A. Emmel, FH Amberg-Weiden, FB MaschinenbauProf. M. Bamberger, Dr. W.D. Kaplan, Technion Haifa, IsraelProf. J. Wilden, TU Illmenau, FertigungstechnikBIAS Bremen, LZH HannoverFraunhofer ILT, IPT, RWTH AachenIWT, IWS Dresden, MPI HalleLURE Paris, ESRF, Grenoble, BESSY, ANKAProf. H.-J. Spies, TU Freiberg, WerkstoffkundeProf. M. Somers, TU Kopenhagen, Materials ScienceProf. E. Mittemeijer, Dr. G. Dehm, MPI StuttgartUni München, Nancy, Leuven, Krakow, Padova, Trento, Jena, Durban, Dortmund, Bratislava, Brno, Budapest, Helsinki, Erlangen, Belgrad, …


Thanks to ….Funding:

DFGUni GöttingenDAAD, EC

Co-workersand Group:

E. Carpene, M. Kahle, A. Müller, F. Landry, M. Han, S. Wagner, C. Illgner, S. Dhar, S. Cusenza, IWT Dresden: J. KasparFH Amberg: A. Emmel, R. Queitsch

FEL@Jefferson Lab: Fred Dylla, Gwyn Williams, Jo Gubeli, Kevin Jordan

•• Your interest and patienceYour interest and patience


You are welcome to visit Göttingen

New Physicsbuilding

free electron laser nitriding of metals - aps physics electron laser nitriding of metals: from basic...

Documents