Diamond-like carbon (DLC) coatings DLC AND INDUSTRY ...€¦ · 2 H 2 gas HiPIMS W 2 C bond layer,...
Transcript of Diamond-like carbon (DLC) coatings DLC AND INDUSTRY ...€¦ · 2 H 2 gas HiPIMS W 2 C bond layer,...
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2015 PPG Undergraduate Research Fellowship ProgramARL
DLC AND INDUSTRY
00.10.20.30.40.50.60.7
0 25 50 75 100 125 150 175 200Co
effic
ien
t o
f fr
ictio
n (
μ)
Distance (m)
DLC on Ti-6Al-4V substrate
Characterization of Diamond-like Carbon
Coatings for Industrial Applications
Sarah K. Newby, Advised by Dr. Douglas E. WolfeMaterials Science and Engineering Dept, Engineering Science and Mechanics Dept.
Applied Research Laboratory, The Pennsylvania State University, University Park PA 168022015 PPG Undergraduate
Research Fellowship Program
Applied Research Laboratoryat the Pennsylvania State University
Tribology Test Results
Coating μ Sample change Ball change
Uncoated 0.541 -0.00159 g -0.00002 g
Cathodic Arc 0.261 -0.00003 g -0.00004 g
PECVD 0.178 -0.00000 g -0.00003 g
Sputtering 0.389 -0.00051 g -0.00005 g
HiPIMS 0.183 -0.00004 g -0.00001 g
Tribology Test Conditions
Temperature 25 ⁰C
Humidity 31-32%
Load 2N
Wear track radius 3.00 mm
Speed 5.00 cm/s
Distance 200 m
Mating Material 100Cr6
-1820
-771
-82
-1477
-2200
-1900
-1600
-1300
-1000
-700
-400
-100
Resid
ual S
tress (
MP
a)
CA PECVD Sput. HiPIMS
0
10000
20000
30000
40000
50000
60000
20 30 40 50 60 70 80 90
Inte
nsity (
Counts
)
Two-theta (Degrees)
Cathodic Arc
25 35 45 55 65 75
Rela
tive Inte
nsity
Two-theta (Degrees)
Cathodic Arc
PECVD
HiPIMS
Hardness (GPa)
Coating Silicon (111) 17-4 PH SS Ti-6Al-4V
Cathodic Arc - - -
PECVD 14.38 22.01 20.21
Sputtering 1.29 1.15 1.05
HiPIMS 26.13 22.33 26.09
Reduced Modulus (GPa)
Coating Silicon (111) 17-4 PH SS Ti-6Al-4V
Cathodic Arc - - -
PECVD 112.65 169.59 161.62
Sputtering 18.88 15.50 15.35
HiPIMS 196.54 187.40 194.74
112.7
18.9
196.5169.6
15.5
187.4161.6
15.4
194.7
14.4
1.3
26.122.0
1.2
22.3 20.2
1.1
26.1
0
10
20
30
40
50
0
50
100
150
200
250H
ard
ness (
GP
a)
Reduced M
odulu
s (
GP
a) Reduced Modulus Hardness
WEAR
TRACK
800 1400 2000
Raman Shift (cm-1)
Preliminary G and D Peak Analysis
Coating Pos(G) FWHM G Pos(D) FWHM D I(D)/I(G)
Cathodic Arc 1550 277.5 - - -
PECVD 1530 120.4 1354 310.1 0.85
Sputtering 1574 151.7 1360 254.7 1.01
HiPIMS 1555 135.3 1349 453.0 0.84
Diamond-like carbon (DLC) coatings
can provide significant cost savings to
industry as they provide:
• Wear resistance
• Corrosion resistance
• Low coefficient of friction
• Tailored hardness
• Multifunctionality
• Improved performance in
extreme environments
Objective:Characterize DLC coatings from
four deposition processes to
identify the operational range
and material properties for
maximizing wear resistance.
Fabrication Methods
Wear Resistance
Surface Morphology
Residual Stress
Mechanical Properties
Phase and Bonding
Optical profilometry of PECVD and magnetron sputtering wear track taken with 25x objective.
Uncoated Cathodic Arc PECVD Sputtering HiPIMS
Measured with Laser interferometry
KLA Tencor Flexus 2320Bragg-Brentano XRD
Grazing Incidence XRD
• All DLCs were found to
be amorphous
• Diffraction from bond
coat observed
• Broad peak between 30-45 degrees corresponding
to HiPIMS bond layer, W2C
• PECVD shows distinct crystal titanium bond coat
which is supported by a thicker bond layer
• Thicker bond coat allows greater compliance to
absorb stress and minimize coating cracking
• Sputtering (orange): No bond coat observed
• FWHM (G) measures
sp2 structural disorder
• I(D)/I(G) measures
the size of the
graphite planes
Silicon (111) substrate 17-4 PH SS substrate Ti-6Al-4V substrate
“Po
p-in E
ven
ts”
“Po
p-in E
ven
ts”
“Po
p-in E
ven
ts”
PECVDPECVDPECVDCA CA CASput. Sput. Sput.HiPIMS HiPIMS HiPIMS
Cathodic Arc PECVD Magnetron Sputtering HiPIMS
Thickness: ~0.7 μm Thickness: ~1.7 μm Thickness: ~3.5 μm Thickness: ~1.7 μm
FE-SEM micrographs of DLC on Si(111) fracture surfaces
• Macroparticles seen on surface of cathodic arc deposited DLC.
• Macroparticles may have contributed to added lubricity and low
coefficient of friction.
• PECVD DLC is a dense coating with fine microstructure.
• Magnetron sputtered DLC shows surface porosity and columnar
microstructure.
• HiPIMS DLC shows surface morphology densification, but still
some evidence of surface porosity.
1 μm 1 μm 1 μm 1 μm
2 μm2 μm2 μm2 μm
DLCDLC
DLC
DLC
Si substrate
Si substrate
Si substrate
Si substrate
Cathodic
Arc PECVD
Plasma Enhanced
Chemical Vapor Deposition
Magnetron
SputteringHiPIMS
High Power Impulse
Magnetron SputteringA high current, low
voltage electric arc is
used to vaporize and
ionize target material
which is then
attracted to a biased
substrate. This
process can eject
macro-particles.
Uses glow discharge to
transfer energy to a gas
mixture. This results in the
decomposition of the gas
molecules into highly
excited species and allows
for gas reactions to occur
at lower temperatures.
Plasma deposition
process where sputtered
material is ejected due to
bombardment of ions.
Incorporation of
magnetic field helps to
retain secondary
electron emission near
the surface of the target.
Based on magnetron
sputtering. Uses high power
densities in short pulses with
a low duty factor. High degree
of ionization creates a dense
plasma in front of the target,
allowing ionization of large
fraction of sputtered material.
The PPG Undergraduate Research Fellowship Program is supported by the PPG Research Foundation through the Materials Research Institute
Cathodic Arc
PECVD
Sputtering
HiPIMS
PECVD
Magnetron Sputtering
HiPIMS
Sputtering
Ternary phase diagram of amorphous carbons. J. Roberson, Diamond-like Amorphous Carbon (2002)
• Low hardness value for magnetron sputtered DLC is a function of the microstructure. These properties most likely contributed to poor wear resistance.
• Compressive stress is favorable for wear resistance
applications (inhibits crack propagation and formation).
• Too much compressive stress can lead to delamination
(often seen when depositing thicker DLC coatings).
Coating Deposition Rate
Cathodic Arc 0.30 μm/hr
PECVD 0.75 μm/hr
Mag. Sputt. 1.40 μm/hr
HiPIMS 0.52 μm/hr
Design ArchitectureCathodic Arc Ti bond layer, graphite target
PECVD Ti bond layer, C6H6 gas
Mag. Sputt. Ti bond layer, graphite, C2H2 gas
HiPIMS W2C bond layer, graphite, C6H6
514.5 nm Raman Spectroscopy
G
G
G
GD
D
D
1800 grating
FWHM(G) = sp3
I(D)/I(G) = sp3
Conclusions:• All DLC coatings reduced the
coefficient of friction by factor of 3-4x
as compared to the uncoated
substrates for the conditions studied.
• PECVD DLC and HiPIMS DLC both
have excellent wear resistance.
• Magnetron sputtered DLC wore down
and exposed the substrate in all
tribology tests.
• DLC deposited by cathodic arc
resulted in the largest compressive
stress.
• Low compressive stress of
magnetron sputtered DLC could be a
result of:
• Surface cracking (observed in
SEM)
• Microstructure (porosity, columnar)
• Less sp3 bonding (observed in
Raman)