Adhesion enhancement of hard coatings by HiPIMS metal ion etching pretreatment and its tribological properties José Antonio Santiago Varela Bilbao, October 19 th 2016 E-mail: jose.santiago@imdea.org
Aim of this work
Aim of this work
Superhard Ion assisted pulsed Magnetron Sputtering Tailored Magnetic Field Configuration No substrate voltage bias required Proprietary technology: Patent application number GB1605162.5 (March 2016)
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.
Implantation Surface preparation Contaminant layers Gradual interface Dangling bonds
HiPIMS High peak powers (500-2000 W/cm 2 ) Reasonable average power Low duty factors (0.5-5%)
Normalized intensity (a.u.) HiPIMS Optical emission Spectroscopy 1.0 Ar DC 0.5 0.0 1.0 W (2+) W (1+) Ar HIPIMS 0.5 0.0 Highly ionized plasma Higher density for coating deposition Enhanced adhesion with pretreatment 300 400 500 600 700 800 900 1000 1100 wavelength (nm)
HiPIMS pretreatment Implantation zone E. Broitman et al, Surf. Coat. Technology 204 (2010) 3349 AP. Ehiasarian et al, Journal of appl. Phys. 101(2007)
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
HiPIMS pretreatment No bias Metal ion etching Bias pretreatment Substrate Substrate
Intensity (a.u.) Intensity (a.u.) HiPIMS pretreatment Optical emission Spectroscopy 90 60 Cr Cr (0) Cr (0) Cr (0) 90 60 Ti (1+) Ti (1+) Ti (1+) Ti 30 Cr (1+) Cr (2+) Cr (1+) 30 Ti (2+) Ti (1+)/Ar(1+) 0 300 400 500 Wavelength (nm) 0 300 400 500 Wavelenght (nm)
HIPIMS pretreatment 120 A (5-6A/cm 2 )
Height (nm) Height (nm) Surface modifications Cr Net deposition <750V Bias Electropolished SS304 substrate Height profile after 1hr etch 500 400 300 600V 750V 200 100 0 Ti -100 300 575V 200 0 100 200 300 400 Displacement ( m) Low Bias voltage achievable! Masked zone Etched zone 100 0-100 -200 0 100 200 300 400 500 Displacement ( m)
Surface modifications Substrate texturing No pretreatment Cr HiPIMS pret Ti HiPIMS pret Roughness (rms) 1.5 6.9 17.4 Under the Mask Out of the Mask Roughness rms: 1.5nm Roughness rms: 17.4nm
Surface modifications
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
TEM Oxygen from the surface is removed Polycrystalline Cr Argon concentration is kept at low level 10-15 nm Fe-Cr interface Low thermal diffussion of Cr Amorphous Cr M2 HSS Steel
TEM Titanium WC Ti M2 Steel Substrate
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
at [%] TEM a-wc Titanium 10nm (implanted + deposited) Ti deposited (5nm) Ti implanted + M2 HSS 60 30 0 Fe Ti W C 60 80 100 distance (nm)
Adhesion Daimler-Benz test No interlayer Bonding layer HiPIMS pretreatment HF6 HF2-3 HF1 Chromium HF6 HF4 HF1 Titanium
Adhesion Nanoscratch L c =500 mn
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) 80 150 220 240 380 Delamination modes Ti Compressive spallation Cr Conformal cracking
Adhesion Nanoscratch
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
Adhesion Pin-on-disk Coating Hardness (GPa) μ Wear rate (m 3 /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
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) 0.31 0.42 0.55
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
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
Eskerrik Thankasko you