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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)