Laser Surface Modification

1
Laser surface coating of bulk metallic glass
composition on high carbon low alloy steel
A. Basu1, J. Dutta Majumdar2, N.B. Dahotre3, I.
Manna2   1Metallurgical Materials Engineering
Department, N.I.T., Rourkela Orissa.
769008 2Metallurgical Materials Engineering
Department, I.I.T., Kharagpur, W.B.
721302 3Department of Materials Science and
Engineering, University of Tennessee, Knoxville,
TN 37996, USA basua_at_nitrkl.ac.in
63rd ATM, 16th November, 2009
2
Bulk Amorphous Alloy
Met-glass is a supercooled liquid with no
long-range periodicity and possessing
near-theoretical strength, large elastic
deformation, high hardness, excellent wear
resistance Klement, Willens, Duwez, Nature, 1960

• Properties of BAAs
• Multi-component alloys
• (dT/dt)Cr ? 103 K/s
• Deep eutectic
• -DHM (enthalpy of mixing)
• h (viscosity) gt 109 Pa-s at Tg
• t (str. relax. time) near TMP

Evolution of Met-glass/BAAs Klement et al.,
Nature (1960) Inoue et al., J. Mater. Sci. Lett.
(1987) Masumoto et al. Jpn.J. Appl.Phy.
(1988) Inoue et al., Mater. Trans JIM
(1991) Peker, Johnson, Appl. Phy. Lett. (1993)
T, K
Liquid

• Mechanical Properties
• High Hardness, Strgth
• High Young Modulus

Crystal
MG
BAAs
t, s
3
Systems
Sl. Year Substrate/deposit Laser Reference
1 1980 Chilled cast iron Nd Glass,pulsed Snezhnoi et al.
2 1980 Cast tool steel /Fe-B (sprayed) CW-CO2 Bergmann-Mordike
3 1981 Fe-2C-12Cr/Fe-B Nb-alloy CW-CO2 Bergmann-Mordike
4 1981 Fe-C/Si-P-B (ternary/quaternary) TEA-CO2 pulsed Borodona et al.
5 1982 Fe-Fe3B, (modulated thin film) NdYAG, pulsed Lin-Spaepen
6 1983 Fe-4 at. B NdYAG, pulsed Lin-Spaepen
7 1984 Mo/Ni (30-60 at), Mo/Co (45 at), Co/Nb (40 at) NdYAG, mode locked Lin et al.
8 1984 Ni-Nb thin film Zr/Cu NdYAG Lin-Spaepen
9 1984 Zr/Cu NdYAG, Q-switched Den Broeder et al.
10 1984 Au- Ti, Co- Ti, Cr- Ti, Zr- Ti Pulsed Affolter-von Allmen
11 1984 Pd-6Cu-16Si CW-CO2 Yoshioka et al.
12 1984 Fe-10Si-15B Pulsed CO2 Kumagai et al.
13 1985 Fe-10Cr-5Mo/12-14 P, C CW-CO2 Yoshioka et al.
14 1985 Pure Ga KrF excimer Frohlingsdorf et al.
15 1987 Mild steel/Ni-Cr-16P-4B CW-CO2 Yoshioka et al.
16 1987 Ni, Cu(Ni), Ti(Ni)/Pd-25Rh-10P-9Si CW-CO2 Kumagai et al.
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Sl. Year Substrate/deposit Laser Reference
17 1988 Nb/Ni-Pt-Pd-Rh CW-CO2 Kumagai et al.
18 1988 Fe-Cr-P-C-Si CW-CO2 Gaffet et al.
19 1990 Review-paper Hashimoto et al.
20 1991 SiC Knotek and Loffler
21 1995 Cu/PdCuSi CW-CO2 and NdYAG Wang et al.
22 1997 AI-Si/Ni-WC Plasma sprayed and laser melted with a CW-CO2 laser Liang and Wong
23 1997 AI-Si/Ni-Cr-B-Si Plasma sprayed and laser melted with a CW-O2 laser Liang and Wong
24 1997 AI-Si/Ni-Cr-AI Plasma sprayed and laser melted with a CW-CO2 laser Liang and Wong
25 1997 Al/Zr60Al15Ni25 Carvalhoa et al.
26 1999 Al alloy/Ni-Cr-Al CW-CO2 Li et al.
27 1999 Ni-Cr-B-Si-C CW-CO2 Li et al.
28 1999 Concrete CW-CO2 Lawrence and Li
29 2000 (Austenitic SS) SiO2 NdYAG Wu and Hong
30 2000 Al alloy/Ni-Cr-B-Si and Ni-Cr-Bi-WC CO2 Wong et al.
31 2000 Al alloy/Ni-Cr-Al CW-CO2 Liang and Su
32 2000 (Austenitic SS) Zr Pulsed NdYAG Wu and Hong
33 2000 Cu/Al2O3 Shepeleva et al.
34 2000 Al-Si/Ni-Cr-Al CW-CO2 Liang et al.
35 2000 (Fe) Fe57Co8Ni8Zr8 CW-CO2 Wu and Hong
36 2001 Fe57Co8Ni8Zr10Si4B13 Xiaolei and Youshi
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SUBSTRATE SAE 52100
Element C Si Mn Cr Fe
Wt 0.95 1.05 0.15 0.35 0.29 0.40 1.50 1.65 Rest
Equivalent grades AISI 52100 (USA), EN 31 (UK),
SUJ 2 (Japan), DIN 100Cr6 (Germany)
BS2S135/535A99 (British), AFNOR100C6 (France)
IS 104Cr6 (India)
Spheroidized annealed
PROCESS LASER COATING Due to possible high
cooling rate ( 106 K/s)
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EXPERIMENTAL
Laser Parameters
Laser 2.5 kW NdYag Beam size 3 mm X 600 µm
Power density 1.39 kW/mm2 Overlap
15 Condition Defocused by 0.5 mm Clad material
Fe48Cr15Mo14Y2C15B6k Power 1.5 and 2.0 kW Scan
speed 2.5 and 3.5 m/min Scan type Single and
double (perpendicular to the first)
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XRD and DSC of PRE-COATED POWDER
XRD of Fe48Cr15Mo14Y2C15B6 powder shows a
characteristic diffuse halo
DSC scan of Fe48Cr15Mo14Y2C15B6 at 200C/min.
Arrow marks the Tg
8
PHASE EVOLUTION STUDY by XRD
Amount of Fe7C decreases with increase in applied
power, scan speed or multiple scan
Laser power 1.5 kW power Scan speed 350
cm/min Type double scan
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SEM and OPTICAL MICROGRAPH (CROSS SECTION)Scan
speed 250 cm/min, scan type single
Laser power 1.5 kW

• Two distinguished zone
• Significant grain coarsening when lased at a
  higher power.

Laser power 2.0 kW
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SURFACE MECHANICAL PROPERTY MICROHARDNESS

• 4 times improvement of base hardness
• Gradual decrease in hardness profile
• With increase in scan speed, surface hardness
  increases and depth of hardened surface zone
  decreases.

11
WEAR

• Test load 4 kg Speed 2.5 mm/s
• Significant improvement in wear resistance was
  achieved
• Kinetics of wear varies with laser parameters.

Ball-on-Plate Wear Tester
2.5 m/min
3.5 m/min
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DEPTH WISE SEM Laser power 2.0 kW, Scan speed
350 cm/min, scan type double
Magnified
Surface
Magnified
Below surface
Away from the surface, the precipitates at the
grain boundaries/interdendritic regions is less.
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DEPTH WISE XRD and WEAR

• Carbide content is most on the surface and
  decrease slowly towards substrate as
  solidification starts near to the substrate.
• Wear resistance is more at surface layer due to
  presence of more amounts of hard phases like
  carbides.

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THERMAL PROFILE MODELLING
At the surface of the sample, the heat balance
between the laser energy absorbed by the sample
and the radiation losses
and
A absorptivity, I laser power intensity, e
emissivity of thermal radiation, tp
irradiation timeT0 ambient temperature s
Stefan-Boltzman constant (5.67 10-8
W/m2K4) Convective boundary condition at the
bottom surface of the sample is given by
h convective heat transfer coefficient, k
thermal conductivity, L sample thickness

• Melting is of amorphous clad precursor only.
• Latent heat of formation of borides, carbides
  etc, are negligible.

Thermal profile on top surface
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SUMMARY

• Attempt to develop amorphous coating by LSC not
  yet successful
• A defect free clad layer/coating with 250 to 600
  mm thickness
• Cellular/dendritic microstructure
• Microhardness improved to as high as 950 VHN as
  compared to 240 VHN of the substrate
• Significant improvement in wear resistance.
• Compressive residual stress in the clad
  layer/coating
• Failure attributed to compositional changes and
  not due to lack of required quenching

Thank you !