E n h a n c e d a d h e s i o n o f D L C c o a t i n g s o n m e t a l l i ca n d i n s u l a t i n g s u b s t r a t e s

San Diego, April 27th, 2017

Dr. Iván Fernández Martínez

Jose Antonio SantiagoJon MolinaMiguel Monclus

Iván Fernández MartínezAmbiorn Wennberg

Raquel González-ArrabalAntonio Rivera

Juan C. Sanchez-LopezCristina T. Rojas

Victor Bellido-González

Outline

- DLC on metal substrates.

- Metal ion etching description.- Comparison between Ti and Cr.- Experimental results.

- DLC on insulating.

- Plasma “biasing” for glass pre-treatment.

Adhesion is a critical issue…

High T applicationsHigh loadsT sensitive substrates such as bearings

Metal ion etching : Arc Bond Sputtering (ABS)

Metal ion etching : HIPIMS

Titanium : higher metal to neutral ratio

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)

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 (1A/cm2)

Metal etching with low bias values reduces arcing issues!!

Ti (3A/cm2)

300 400 5000

30

60

90

Inte

nsity (

a.u

.)

Wavelenght (nm)

Ti (1+)Ti (1+)Ti (1+)

Ti (2+)

Ti (1+)/Ar(1+)

Ti

1000A

650V

Titanium : higher metal to neutral ratio

1A/cm2

3A/cm2

Low Bias values : Reduced arcing issues!!!

Net deposition

Etching

Etching conditions to prevent amorphous layer formation

1) Ar glow discharge

2) Ti/Cr metal etching

3) WC/CrC layer

4) DLC layer

Ti/Cr extra bonding layer

WC/CrC layer

DLC layer

DLC coating sequence (1 m thick DLC)

DLC

HSS

WCM2 HSS

WC

Ti

Ti interface

Ti metal etching + Ti extra bonding layer: TEM

Local epitaxy between HSS substrate and Ti bonding layer

No external heating

M2 HSS

Ti layer

Ti metal etching + Ti extra bonding layer: SAED

NO Crystalline alignment between substrate and Cr bonding layer

Cr metal etching + Cr extra bonding layer: SAED

1

2

M2 HSS

1

2

Ti HIPIMS etch Cr HIPIMS etchAr glow discharge

1 m thick WC/DLC onto pre-treated HSS M6

Ar etching Ar etching +Ti bonding layer

Ar etching+Ti HiPIMS

Ar etching +Cr bonding layer

Ar etching + Cr HiPIMS

Critical Load (mN) 80 150 220 240 380

Delamination modes

Conformal cracking

Compressive spallation

Ti

Cr

Nanoscratch tests for 1um thick WC:DLC coating on HSS

Composition along the interface : EELS

Ti-L2,3 Fe-L2,3

C-K

Ti-L2,3

O-K

C-K

Central area Ti extra bonding

Ti, Fe signals : 2-3nm overlap implantation?

nm0

15

Are we doing the HIPIMS metal etching correctly?

50N

60N

55N

0 N 200 N

65N

Cr Bonding layer (15nm)

WC (0.2m)

C-DLC (2m)

2.4 m thick DLC layer stack : Ar glow discharge + Cr bonding

HSS (60HRC)

70N

80N

85N

90N

75N

HiPIMS pret.

C-DLC (2m)

WC (0.2m)

Cr Bonding layer (15nm)

HSS (60HRC)

2.4 m thick DLC layer stack : HIPIMS Cr metal etching + Cr extra b.

What about insulating substrates?

T h i n D L C < 1 0 n m o n d i s p l a y c o v e r p a n e l .

Black : Glass reference = 89.2%Red : 3nm DLC = 88.2%Green : 5nm DLC = 88.0%

Anti scratch glass

D L C c o a t i n g o n G l a s s

Hardness in the range of 20GPa for 400nm thick DLC layer

DLC

Glass

Positive ion assistance by plasma “biasing”

Magnetronpeak current

+150V (Plasma OFF)

-20V at plasma ON

Voltage

Magnetronpeak current

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

V/I at magnetron Floating potential at substrate

D L C c o a t i n g o n G l a s s

Substrate can be pre-treated with reactive gases such as oxygen

+485V

Current to floating potential (10mV/A)

Treated

Masked (Treated)

Coated

D L C c o a t i n g o n G l a s s – m o r p h o l o g y c h a n g e

8006004002000

8

7

6

5

4

3

2

1

0

X[nm]

Z[n

m]

8006004002000

12

10

8

6

4

2

0

X[nm]

Z[n

m]

Untreated glass substrate

Oxygen treated glass substrate

RMS roughness : 2.6 nm

RMS roughness : 1.4 nm

S c r a t c h t e s t s : T a b e r a b r a s i o n

DLC Coating description

Total light

transmission (400-

700nm)

Taber test result

15 min O2 plasma cleaning + 6nm DLC 89.2 ≤20 times NG

5 min O2 plasma cleaning + 6nm DLC 91.0 ≤15 times NG

5 min O2 plasma etching + 3nm DLC 91.2 ≤10 times NG

Load 7.5N

15min plasma cleaning with V positive pulses enhances abrasion performance

Conclusions

- Metal etching enhances DLC adhesion on steel.

- Cr shows better performance than Ti

- Plasma “biasing” for glass pre-treatment.