Adhesion enhancement of DLC hard coatings by HiPIMS metal ion etching pretreatment and its

tribological properties

José Antonio Santiago Varela

Bilbao, October 19th 2016

E-mail: jose.santiago@imdea.org

DLCAim of this work

DLCAim of this work

DLCSuperhard DLC

Proprietary technology: Patent application number GB1605162.5 (March 2016)

• Ion assisted pulsed Magnetron Sputtering

• Tailored Magnetic Field Configuration

• No substrate voltage bias required

DLCCoatings architecture

Argon etching Buffer layer DLC coating

Argon etching Bonding layer Buffer layer DLC coating

Bonding layer (Cr/Ti)

Buffer layer (WC)

DLC coating

Buffer layer (WC)

DLC coating

Argon etching HiPIMS pret. Bonding layer Buffer layer DLC coating

DLC coating

Buffer layer (WC)

Bonding layer (Cr/Ti)

HiPIMS pret.

DLCImplantation

Surface preparation

• Contaminant layers

• Gradual interface

• Dangling bonds

DLCHiPIMS

• High peak powers (500-2000 W/cm2)

• Reasonable average power

• Low duty factors (0.5-5%)

DLCHiPIMS

Ar

300 400 500 600 700 800 900 1000 1100

0.0

0.5

1.0

0.0

0.5

1.0

wavelength (nm)

Norm

aliz

ed inte

nsity (

a.u

.)

W (2+)W (1+)

Ar

DC

HIPIMS

Optical emission Spectroscopy

• Highly ionized plasma• Higher density for coating deposition• Enhanced adhesion with pretreatment

DLCHiPIMS pretreatment

E. Broitman et al, Surf. Coat. Technology 204 (2010) 3349 AP. Ehiasarian et al, Journal of appl. Phys. 101(2007)

Implantationzone

as Bias up to 1200V as regular HIPIMS

Cr bias

Ti bias

Cr magnetron

Ti magnetron

Vb= -750 (V)Jb= 30 (mA/cm2)

Vb= -450 (V)Jb= 150(mA/cm2)

VHiP= 1100 (V)JHIP= 1 (A/cm2)

VHiP= 600 (V)JHIP= 5 (A/cm2)

DLCHiPIMS pretreatment

DLC

Metal ion etching

No biasBias

pretreatment

Substrate

Substrate

HiPIMS pretreatment

DLCHiPIMS pretreatment

300 400 500

0

30

60

90

Inte

nsity (

a.u

.)

Wavelength (nm)

Cr (1+)

Cr (2+)

Cr (0)

Cr (1+)

Cr (0)

Cr (0)

Optical emission Spectroscopy

300 400 5000

30

60

90

Inte

nsity (

a.u

.)

Wavelenght (nm)

Ti (1+)

Ti (1+)Ti (1+)

Ti (2+)

Ti (1+)/Ar(1+)

Cr Ti

DLC

120 A (5-6A/cm2)

HIPIMS pretreatment

DLCSurface modifications

0 100 200 300 400

-100

0

100

200

300

400

500

600V

750V

He

igh

t (n

m)

Displacement (m)

0 100 200 300 400 500

-200

-100

0

100

200

300

575V

He

igh

t (n

m)

Displacement (m)

Low Bias voltage achievable!

Net deposition <750V Bias

Etched zone

Height profile after 1hr etch

Masked zone

Electropolished SS304 substrateCr

Ti

DLC

Roughness rms: 1.5nm Roughness rms: 17.4nm

Under the Mask Out of the Mask

Substrate texturing

Surface modifications

No pretreatment Cr HiPIMS pret Ti HiPIMS pret

Roughness (rms) 1.5 6.9 17.4

DLCSurface modifications

DLCTEM

Chromium

• Polycrystalline Cr bonding layer

• Dense amorphous Cr interface by

HiPIMS pretreatement

• No bubbles, voids or droplets

• Gradual interface coating-substrate

Amorphous Cr

Crystalline Cr

M2 HSS Steel

WC

DLCTEM

• Oxygen from the surface is removed

• Argon concentration is kept at low level

• 10-15 nm Fe-Cr interface

• Low thermal diffussion of Cr

Polycrystalline Cr

Amorphous Cr

M2 HSS Steel

DLCTEM

Titanium

DLC

WC

M2 Steel Substrate

Ti

DLCTEM

WC

Ti deposited

+ HSSTi implanted

Titanium

• Gradual interface coating-substrate

• Epitaxial growth

• Alligment from steel substrate to WC

• Ti implanted into the substrate lattice

• No bubbles, voids or droplets

DLCTEM

Ti deposited (5nm)

a-WC

60 80 100

0

30

60

Fe

Ti

W

C

at

[%]

distance (nm)

Titanium 10nm (implanted + deposited)

Ti implanted + M2 HSS

DLCAdhesion

HiPIMS pretreatmentBonding layerNo interlayer

Chromium

Titanium

HF6

HF6

HF2-3

HF4

HF1

HF1

Daimler-Benz test

DLCAdhesion

Lc=500 mN

Nanoscratch

DLCAdhesion

No bonding layer Ti bonding layer Ti HiP pret Cr bonding layer Cr HiP pret

Critical Load (mN) 80 150 220 240 380

• Conical indenter R= 10 µm

• HSS M2 polished substrate

• Loading rate= 2.5 mN/s

• Scratch length 500 µm

Delamination modes

Conformal cracking

Compressive spallationTi

Cr

DLCAdhesion

Nanoscratch

DLCAdhesion

50N

97N

66N

110N 135N

88N

• Extraordinary adhesion in scratch tests• First cracks. Lc1= 100 N• Delamination load. Lc2= 135 N

Macroscratch

DLCAdhesion

Coating Hardness (GPa) μ Wear rate (m3/Nm)

a-C 30 0.2 10-15

a-C:H (Low H) 25 0.17 10-15

a-C:H (High H) 10 0.10 3·10-15

Pin-on-disk

DLCAdhesion

No interlayer Cr bonding layer Cr HiPIMS pret.

Máx. Sliding speed (m/s) 0.31 0.42 0.55

Test conditions ASTM G99P=10 N; ω= 200 rpm; Ball diameter= 6 mm; v= 0.5 m/s

DLCConclusions

1. HiPIMS metal ion etching pretreatment improves adhesion by controlling:

• Surface morphology

• Chemical composition

• Growth modes

2. Degree of ionization is a key factor for the application of HiPIMS pretreatment

3. Cr HiPIMS pretreatment enhances considerably adhesion of DLC coatings

4. Nanoscratch and nanoimpact testing are valuable tools to assess thetribomechanical response of DLC coatings

José Miguel GARCIA MARTINDavid FUSTER

Raquel GONZÁLEZ ARRABALAntonio RIVERA

Miguel CASTILLOJon MOLINA

Miguel MONCLÚS

Víctor BELLIDO-GONZÁLEZFrank PAPA

Iván FERNÁNDEZ MARTÍNEZAmbiorn WENNBERG

DLCThank youEskerrik asko