Wear resistant and low friction nanocomposite coatings Dr Tomasz Suszko

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 2 Plasma sputtering – short description DC-, triode-, RF-, magnetron sputtering Nonreactive and reactive mode Low friction nanocomposite coatings Chosen results: Mo 2 N/Cu nancristaline films – structure, mechanical and tribological properties Structure, hardness Friction & wear mechanisms in temperature range RT-400°C Lecture outline

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko Plasma - the 4 th state of matter

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 4 Fundamentals of plasma sputtering – DC sputtering (diode sputtering) - + Cathode Anode + substrate Pressure ~10 Pa noble gas (e.g. Ar) Voltage ~1.5 kV Electron emission Sputtering Implantation Defects generation E-m radiation Ionisation coeffcient Electron energy [eV] Disadvantages: Low ion current density (low sputtering rate) High working gas pressure resulting in scattering (low deposition rate) Dielectric materials can not be sputtered High voltage is needed

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko V Target 0.5 kV - + Substrate Ionisation coeffcient Electron energy [eV] Lower working gas pressure – 0.1 Pa (higher deposition rate) +Higher ion current density (higher sputtering rate) –Dielectric materials can not be sputtered Fundamentals of plasma sputtering – triode sputtering

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 6 Ionisation coeffcient Electron energy [eV] Lower working gas pressure – 0.1 Pa (higher deposition rate) +Higher ion current density (higher sputtering rate) –Dielectric materials can not be sputtered Fundamentals of plasma sputtering – microwave assisted sputtering Target 0.5 kV – + Substrate Microwave antenna

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 7 Substrate Fundamentals of plasma sputtering – RF sputtering RF Matchbox The differce in: mobility of electrons and ions areas of electrodes results in negative target selfbias thus, dielectric materials can be sputtered

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 8 Fundamentals of plasma sputtering – motion of the electron in electromagnetic field R L v e cos   v e v e sin 

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 9

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 10

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 11 There is a possibility to control the substrate ion current and the energy of the ions as well – unbalanced magnetron sputtering Substrate Fundamentals of plasma sputtering – magnetron sputtering DC or pulsed power supply Ionisation coeffcient Electron energy [eV] Low working gas pressure – 0.1 Pa +Very high ion current density is possible (high sputtering rate)

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 12 What materials can be sputtered and deposited? Whatever one need? It must be kept in mind that: Compounds, targets are made of, are decomposed to the atomic form and only then can react again on the substrate (not always getting appropriate conditions) Sputtered atoms are scattered along their way towards substrate (the lighter the more intense thus the stoichiometry can change) A sputtered compound can not to easily evaporate (sufficient vacuum can not be obtain)

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 13 End of part one

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 14 Mean free path Secondary electron emmision Ion implantation Sputtering Charging effect Thermoemission Magnetic mirror and trap Larmor frequency and radius Magnetron source (gun) From yesterday

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 15 Fundamentals of plasma sputtering – reactive sputtering Compounds of the target and gas elements For poorly conducting or insulator deposits pulsed power supply is very usefull Pumping system Inert gas (e.g. Ar) Reactive gas (N 2, O 2, CH 4 etc.) Optical signal (optical emission spectroscopy) Gas pressure Gas flows Discharge power (Substrate bias – energy of the ions) (Substrate ion current density) Control unit

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 16 What I won’t speak about is... Plasma enhanced chemical vapour deposition Laser ablation Plasma spraying Ion implantation (clasical or plasma immersion) Plasma nitriding or carburazing etc.

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 17 Plasma maintained by: DC or pulsed discharge (magnetron), Vacuum arc, RF e-m waves Plasma maintained by: DC or pulsed discharge (magnetron), Vacuum arc, RF e-m waves Working gases: Ar (inert gas), N 2 (for nitrides), O 2 (for oxides), CH 4, C 2 H 2 (for carbides and DLC) Working gases: Ar (inert gas), N 2 (for nitrides), O 2 (for oxides), CH 4, C 2 H 2 (for carbides and DLC) Targets made of: Ti, Al, Mo, V, Ag, Cu but also Fe, Ni, Co and Si Targets made of: Ti, Al, Mo, V, Ag, Cu but also Fe, Ni, Co and Si What we use for deposition is...

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 18 Coils supply Pulsed power supply Substrate bias and heating Pulsed power supply Spectrometer Pumping system Optical signal Gases Valve unit Magnetron sources What we develop for process control and data acquisition is...

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 19 F L What we interest in is... Continuous looking for novel anti-wear coatings and development of their deposition methods Phenomena in the tribolgical contact between hard coated surface and a counterpart Structure, elemental and phase composition of the coatings in the initial state (after deposition) Stress, adhesion, hardness of the coatings Friction during tribological tests (especially in elevated temperatures) Tribomutation - chemical and physical changes of the „third body” – elemental and phase composition, structure etc. of that The role of oxides in friction process

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 20 Where can we look for hard compounds?

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 21  Chemical sythesis ( DLC, c-BN, AlMgB, C 3 N 4 )  Forming proper physical microstructure Nitride or carbide multilayers (TiN/CrN, TiN/TiAlN i in.) Composites nc-Me x N/a-Si 3 N 4 nc-Me x C/a-C:H np. nc-TiN/a-Si 3 N 4 Composites Me x N/M np. (ZrN/Cu, Cr 2 N/Cu, TiN/Ag) How to obtain hard films

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 22  Shear strength and hardness depend on each other thus friction coefficients are comparable for various izotropic materials. Hardness is not all - there is friction also! Shear strength Hardness F L A large small large Soft materials F L Hard materials A

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 23 F L Self-lubricating materials As a result of rubbing, a thin low-shear- -strengh layer should appear The material should be hard (what ensures small contact area) Composite materials: guaiac wood PTFE impregnated bronzes bearing metals with graphite or MoS 2 inclusions ceramic/carbon fiber composites Izotropic materils: diamond

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 24 RTDinfo - Mag. Europ. Res., 39, 2003 Self-lubricating FILMS Hard coating Enviromental gas Lubricating film

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 25 Mo 2 N as a hard coating MoO 3 as a solid lubricant Cu additive as a mean for hardness enhancement An attempt - Mo 2 N/Cu coatings

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 26 Mo 2 N/Cu nanocrystalline films – s tructure, mechanical and tribological properties Suszko et al., Surf. Coat. Tech., 200, 2006, pp Suszko et al., Surf. Coat. Tech., 194, 2005, pp Outline 1. Deposition method 2. Some remarks on the structure 3. Hardness of the films 4. Friction & wear in temperature range RT-400°C 5. Conclusions

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 27 Deposition method: unbalanced magnetron sputtering pulsed power supply pulsed power supply sample external coils pumps Ar, N 2 Mo Cu optical signal 30 cm Temperature: 200 °C Bias: -30 V

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 28 Structure – XRD spectra Intensity [a.u.] Fe (substrate) 0% at. Cu 1% at. Cu 6% at. Cu 9% at. Cu 21% at. Cu Diffraction angle 2ϑ [°] ← γ-Mo 2 N (111) γ-Mo 2 N (200)→ ← Cu (111) Cu (200)→ Co K α radiation

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 29 Cu content (at. %) Crystallite size [nm] Mo 2 N (200) Crystallite size obtained from Scherrer’s formula AFM image of the pure γ–Mo 2 N nitride The influence of copper content on crystalite size

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 30 Structure Crystallite size and film hardness Cu content (% at.) Crystallite size (nm) Mo 2 N (111) Mo 2 N (200) Cu content (% at.) H (GPa) Load-depth sensitive method DUH 202 (F N 20 mN) Load-depth sensitive method Hysitron (F N 2mN) Traditional method (F N 100—1000 mN)

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko Temperature [°C] Friction coefficient 0 % at. Cu 3 % at. Cu 7 % at. Cu 22 % at. Cu Fixed and scanned temperature TiN Friction coefficient Ball on disc configuration Counterpart: alumina ball Speed: 5 cm/s Normal force: 1 N

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 32 Wear rate coefficient - a definition Worn volume of the sample per work unit done against friction force b) 100°C μmμm μmμm Revolution number Friction coefficient

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 33 Wear behavior: °C Copper content (at. %) Wear rate ( m 3 /J ) °C 300°C RT, 200°C 100°C Wear rate for TiN RT – 0.8· °C – 1.5· °C – 3·10 -15

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 34 Wear behavior – "100°C effect" RT: k F ~ m 3 / 100°C: k F ~2· m 3 /J ! 200°C: k F ~ m 3 /J Raman shift [cm -1 ] Out In Raman shift [cm -1 ] Out In Raman shift [cm -1 ] Out In Mo 2 N 0% Cu

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko at. % Cu 50  m 9 at. % Cu 50  m 22 at. % Cu 0 at. % Cu 50  m 1 at. % Cu 50  m 2.5 at. % Cu Wear behavior – the influence of Cu addtion (100°C friction test) k F ~ m 3 /Jk F ~2· m 3 /J

International Student Summer School „Nanotechnologies in materials engineering” Warsaw - Koszalin 2006 Tomasz Suszko 36 Conclusions Relatively low friction coefficient against alumina is observed in room temperature. 1-3 at. % of Cu additive increases hardness of Mo 2 N coatings. Low wear rate is registered in temperatures bellow 250°C. "The 100°C effect" is observed for samples with low content of copper. This effect is eliminated when films contain >6 at. % Cu. Coatings gradually oxidize in temperature over 300°C.