Adhesion enhancement of DLC hard coatings by HiPIMS metal ion etching pretreatment and its tribological properties José Antonio Santiago Varela

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1 Adhesion enhancement of hard coatings by HiPIMS metal ion etching pretreatment and its tribological properties José Antonio Santiago Varela Bilbao, October 19 th

2 Aim of this work

3 Aim of this work

4 Superhard Ion assisted pulsed Magnetron Sputtering Tailored Magnetic Field Configuration No substrate voltage bias required Proprietary technology: Patent application number GB (March 2016)

5 Coatings architecture Argon etching Buffer layer coating Argon etching Bonding layer Buffer layer coating Argon etching HiPIMS pret. Bonding layer Buffer layer coating coating coating coating Buffer layer (WC) Buffer layer (WC) Bonding layer (Cr/Ti) Buffer layer (WC) Bonding layer (Cr/Ti) HiPIMS pret.

6 Implantation Surface preparation Contaminant layers Gradual interface Dangling bonds

7 HiPIMS High peak powers ( W/cm 2 ) Reasonable average power Low duty factors (0.5-5%)

8 Normalized intensity (a.u.) HiPIMS Optical emission Spectroscopy 1.0 Ar DC W (2+) W (1+) Ar HIPIMS Highly ionized plasma Higher density for coating deposition Enhanced adhesion with pretreatment wavelength (nm)

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

10 HiPIMS pretreatment Cr bias V b = -750 (V) J b = 30 (ma/cm 2 ) Cr magnetron V HiP = 1100 (V) J HIP = 1 (A/cm 2 ) Ti bias V b = -450 (V) J b = 150(mA/cm 2 ) Ti magnetron V HiP = 600 (V) J HIP = 5 (A/cm 2 ) as Bias up to 1200V as regular HIPIMS

11 HiPIMS pretreatment No bias Metal ion etching Bias pretreatment Substrate Substrate

12 Intensity (a.u.) Intensity (a.u.) HiPIMS pretreatment Optical emission Spectroscopy Cr Cr (0) Cr (0) Cr (0) Ti (1+) Ti (1+) Ti (1+) Ti 30 Cr (1+) Cr (2+) Cr (1+) 30 Ti (2+) Ti (1+)/Ar(1+) Wavelength (nm) Wavelenght (nm)

13 HIPIMS pretreatment 120 A (5-6A/cm 2 )

14 Height (nm) Height (nm) Surface modifications Cr Net deposition <750V Bias Electropolished SS304 substrate Height profile after 1hr etch V 750V Ti V Displacement ( m) Low Bias voltage achievable! Masked zone Etched zone Displacement ( m)

15 Surface modifications Substrate texturing No pretreatment Cr HiPIMS pret Ti HiPIMS pret Roughness (rms) Under the Mask Out of the Mask Roughness rms: 1.5nm Roughness rms: 17.4nm

16 Surface modifications

17 TEM WC Chromium Polycrystalline Cr bonding layer Crystalline Cr Dense amorphous Cr interface by HiPIMS pretreatement Amorphous Cr No bubbles, voids or droplets M2 HSS Steel Gradual interface coating-substrate

18 TEM Oxygen from the surface is removed Polycrystalline Cr Argon concentration is kept at low level nm Fe-Cr interface Low thermal diffussion of Cr Amorphous Cr M2 HSS Steel

19 TEM Titanium WC Ti M2 Steel Substrate

20 TEM Titanium WC Gradual interface coating-substrate Ti deposited Epitaxial growth Ti implanted + HSS Alligment from steel substrate to WC Ti implanted into the substrate lattice No bubbles, voids or droplets

21 at [%] TEM a-wc Titanium 10nm (implanted + deposited) Ti deposited (5nm) Ti implanted + M2 HSS Fe Ti W C distance (nm)

22 Adhesion Daimler-Benz test No interlayer Bonding layer HiPIMS pretreatment HF6 HF2-3 HF1 Chromium HF6 HF4 HF1 Titanium

23 Adhesion Nanoscratch L c =500 mn

24 Adhesion Conical indenter R= 10 µm HSS M2 polished substrate Loading rate= 2.5 mn/s Scratch length 500 µm No bonding layer Ti bonding layer Ti HiP pret Cr bonding layer Cr HiP pret Critical Load (mn) Delamination modes Ti Compressive spallation Cr Conformal cracking

25 Adhesion Nanoscratch

26 Adhesion Macroscratch Extraordinary adhesion in scratch tests First cracks. L c1 = 100 N Delamination load. L c2 = 135 N 50N 66N 88N 97N 110N 135N

27 Adhesion Pin-on-disk Coating Hardness (GPa) μ Wear rate (m 3 /Nm) a-c a-c:h (Low H) a-c:h (High H)

28 Adhesion Test conditions ASTM G99 P=10 N; ω= 200 rpm; Ball diameter= 6 mm; v= 0.5 m/s No interlayer Cr bonding layer Cr HiPIMS pret. Máx. Sliding speed (m/s)

29 Conclusions 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 coatings 4. Nanoscratch and nanoimpact testing are valuable tools to assess the tribomechanical response of coatings

30 Miguel CASTILLO Jon MOLINA Miguel MONCLÚS Raquel GONZÁLEZ ARRABAL Antonio RIVERA José Miguel GARCIA MARTIN David FUSTER Víctor BELLIDO-GONZÁLEZ Frank PAPA Iván FERNÁNDEZ MARTÍNEZ Ambiorn WENNBERG

31 Eskerrik Thankasko you