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Tribology And Wear Out Of Mechanisms Verhaert Space

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Tribology & wear out of Mechanisms. Presentation on Innovation Day 07 by Verhaert Space

Tribology & wear out of Mechanisms. Presentation on Innovation Day 07 by Verhaert Space

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  • 1. © VERHAERT SPACE Tribology & wear-out of mechanisms VERHAERTINNOVATIONDAY – OCTOBER 12th, 2007 www.mastersininnovation.com Tribology and wear-out of mechanisms Luc Bierque Luc.bierque@verhaertspace.com www.verhaertspace.com Commercially confidence – This presentation contains ideas and information which are proprietary of VERHAERT SPACE, it is given in confidence. You are authorized to open and view the electronic copy of this document and to print a single copy. Otherwise, the material may not in whole or in part be copied, stored electronically or communicated to third parties without prior agreement of VERHAERT SPACE. www.mastersininnovation.com 12.10.2007 Slide 1 CONFIDENTIAL
  • 2. © VERHAERT SPACE Tribology & wear-out of mechanisms www.mastersininnovation.com Introduction 12.10.2007 Slide 2 CONFIDENTIAL
  • 3. © VERHAERT SPACE Tribology & wear-out of mechanisms Introduction (1/3): Purpose It’s important to keep wear out under control, think at: www.mastersininnovation.com • Downtime of production. • People involved in repair and maintenance • Loss of mission (space application) However, beating wear is much more than the introduction of high-tech solutions, it is very important to apply the correct methodology/approach. 12.10.2007 Slide 3 CONFIDENTIAL
  • 4. © VERHAERT SPACE Tribology & wear-out of mechanisms Introduction (2/3): What affects wear? • Contact load/stress www.mastersininnovation.com • Hardness • Existence of oxidation films • Temperature • Ambient/working pressure (e.g. adhesive wear in vacuum) • Working conditions: corrosion, speed, vibrations • The surface microstructure and surface condition • The choice of material pairs • … 12.10.2007 Slide 4 CONFIDENTIAL
  • 5. © VERHAERT SPACE Tribology & wear-out of mechanisms Introduction (3/3): What is Tribology? “ Science and technology of interactive surfaces in relative motion www.mastersininnovation.com w.r.t. each other and related subjects/practices”. It covers the subject of friction, wear and lubrication. It’s all around us… 12.10.2007 Slide 5 CONFIDENTIAL
  • 6. © VERHAERT SPACE Tribology & wear-out of mechanisms www.mastersininnovation.com Methodology followed by Verhaert Space 12.10.2007 Slide 6 CONFIDENTIAL
  • 7. © VERHAERT SPACE Tribology & wear-out of mechanisms Methodology: 1. Select between wet and dry lubrication www.mastersininnovation.com (this sets the initial working conditions). 2. Avoid a poor design, operation/functioning of your mechanism. 3. Analyze/ assess contact loads/stresses, bending stresses, … 4. Assess/analyze the wear aspects/phenomenon. 5. Make final decision on tribological selection. 6. Perform functional, friction/wear and life test. 12.10.2007 Slide 7 CONFIDENTIAL
  • 8. © VERHAERT SPACE Tribology & wear-out of mechanisms 1. Select between wet and dry lubrication (this sets the initial working conditions). www.mastersininnovation.com 2. Avoid a poor design, operation/functioning of your mechanism. 3. Analyze/ assess contact loads/stresses, bending stresses, … 4. Assess/analyze the wear aspects/phenomenon. 5. Make final decision on tribological selection. 6. Perform functional, friction/wear and life test. 12.10.2007 Slide 8 CONFIDENTIAL
  • 9. © VERHAERT SPACE Tribology & wear-out of mechanisms 1-Select between wet and dry lubrication (1/3): Overview Wet/liquid lubrication: Solid/dry lubrication: www.mastersininnovation.com • Oil. • Lamellar solids (MoS2, graphite). • Grease. • Self lubricating materials (polymers, bronzes…). • Surface treatments/coatings. • Ceramic materials. • Nanomaterials/composites •… 12.10.2007 Slide 9 CONFIDENTIAL
  • 10. © VERHAERT SPACE Tribology & wear-out of mechanisms 1-Select between wet and dry lubrication (2/3): Wet lubrication: Pro & cons + - www.mastersininnovation.com • Allows high duty & high speed • Vapor pressure: evaporation loss operation (oil) • Limited temperature range • Possibility of hydrodynamic (-70 to + 250 deg. C) lubrication (oil) • Viscosity is temperature & pressure • Thermal conduction superior to dependant most solid lubricants • Surface migration & leaks: requires • Do not generate wear debris seals • Relatively cheap and easily applied • Lubrication regime is speed • Minimum torque noise dependant (does not support • In most cases offers additional accelerated life test) corrosion protection • Removal (oil filter) & means for • Degradation of oil over time detection of wear particles • Not allowed for some application (magnetic) (medical, food…) 12.10.2007 Slide 10 CONFIDENTIAL
  • 11. © VERHAERT SPACE Tribology & wear-out of mechanisms 1-Select between wet and dry lubrication (3/3): Dry lubrication: Pro and con’s + - www.mastersininnovation.com • Negligible vapor pressure (OK in • Generation of wear debris vacuum and low pressures) • Friction/wear can be sensitive to • No surface migration/creep (avoids moisture/water (e.g. MoS2). the use of seals) • Life limited by lubricant wear. • Wide operational temperature range • Wear rate is often independent of • Adherence of coatings can be speed (supports accelerated life cumbersome. test) • Electrically conductive • Avoids start up wear (e.g. wet on dry) • Applications where oil/grease is not allowed (food/medical). • … 12.10.2007 Slide 11 CONFIDENTIAL
  • 12. © VERHAERT SPACE Tribology & wear-out of mechanisms 1. Select between wet and dry lubrication (working conditions). www.mastersininnovation.com 2. Avoid a poor design, operation/functioning of your mechanism. 3. Analyze/ assess contact loads/stresses, bending stresses, … 4. Assess/analyze the wear aspects/phenomenon. 5. Make final decision on lubrication/technology/materials. 6. When possible/required: perform functional, friction/wear and life test. 12.10.2007 Slide 12 CONFIDENTIAL
  • 13. © VERHAERT SPACE Tribology & wear-out of mechanisms 2-Avoid a poor design (1/3): Mechanism design drivers www.mastersininnovation.com • Implementation of wet/dry lubrication. • Available space/volume and mass. • Loading/forces/torque. • Speed, precision, stiffness, allowable misalignments. • Loads. • Required lifetime • Environmental conditions (temperature, pressure, vibration/shock…). • Vibration/noise levels (quiet running). • Friction. • Allowable/required materials. •… 12.10.2007 Slide 13 CONFIDENTIAL
  • 14. © VERHAERT SPACE Tribology & wear-out of mechanisms 2-Avoid a poor design (2/3): Design & operation aspects • Implement preloading: to avoid fretting wear, slippage of bearing balls… Soft preloading: www.mastersininnovation.com Insensitive to different thermal expansion (CTE). Hard/rigid preloading: Higher rigidity. 12.10.2007 Slide 14 CONFIDENTIAL
  • 15. © VERHAERT SPACE Tribology & wear-out of mechanisms 2-Avoid a poor design (3/3): Design & operation aspects www.mastersininnovation.com Design for the correct stiffness <> contact load: • “Back to back” bearing configuration. • “Face to Face” bearing configuration. • Selection of contact angle. Back-to-back arrangement Face-to-face arrangement Tandem arrangement 12.10.2007 Slide 15 CONFIDENTIAL
  • 16. © VERHAERT SPACE Tribology & wear-out of mechanisms 1. Select between wet and dry lubrication (working conditions). www.mastersininnovation.com 2. Avoid a poor design, operation/functioning of your mechanism. 3. Analyses aspects to be covered 4. Assess/analyze the wear aspects/phenomenon. 5. Make final decision on lubrication/technology/materials. 6. When possible/required: perform functional, friction/wear and life test. 12.10.2007 Slide 16 CONFIDENTIAL
  • 17. © VERHAERT SPACE Tribology & wear-out of mechanisms 3- Analysis aspects to be covered (1/1) Aspect Space Industrial www.mastersininnovation.com applications applications Stress/strength/ stifness of mechanical parts Yes Yes Fatigue/fracture Yes Yes Preload/tolerance analysis Yes Yes Thermo elastic deformation Yes Yes Hertzian contact stresses Yes Yes Shock/vibration generation & susceptability Yes In most cases Life prediction Always test Prediction Required forces/ drive torques etc. Test + Prediction or analysis test 12.10.2007 Slide 17 CONFIDENTIAL
  • 18. © VERHAERT SPACE Tribology & wear-out of mechanisms 1. Select between wet and dry lubrication (working conditions). www.mastersininnovation.com 2. Avoid a poor design, operation/functioning of your mechanism. 3. Analyze/ assess contact loads/stresses, bending stresses, … 4. Assess/analyze the wear aspects 5. Make final decision on lubrication/ technology/ materials. 6. When possible/required: perform functional, friction/wear and life test. 12.10.2007 Slide 18 CONFIDENTIAL
  • 19. © VERHAERT SPACE Tribology & wear-out of mechanisms 4-Assess/analyse the wear aspects (1/6) www.mastersininnovation.com This requires understanding of the basic wear theory/ tribology. Existing myths (see further: some examples given). 12.10.2007 Slide 19 CONFIDENTIAL
  • 20. © VERHAERT SPACE Tribology & wear-out of mechanisms 4-Assess/analyse the wear aspects (2/6) Myth 1: “Engineering surfaces are flat, smooth and clean”. www.mastersininnovation.com Surfaces are never smooth/flat, the degree of roughness depends on the level of examining the surface. Surfaces are always contaminated: this can help against adhesion but can be a burden w.r.t. adhering a lubricant coating etc. Surface machined by conventional process 12.10.2007 Slide 20 CONFIDENTIAL
  • 21. © VERHAERT SPACE Tribology & wear-out of mechanisms 4-Assess/analyse the wear aspects (3/6) Myth 2: “The larger the area in contact, the larger the friction”. www.mastersininnovation.com Zero friction does not exist. The friction force is proportional to the applied load: Fw = N * f or f= Fw/N, tg(fi)=Fw/N (f = friction coefficient, which is unit less) fi N Fw F F G G Fw N 12.10.2007 Slide 21 CONFIDENTIAL
  • 22. © VERHAERT SPACE Tribology & wear-out of mechanisms 4-Assess/analyse the wear aspects (4/6) Myth 3: “When in contact, bodies touch of their entire surface area”. www.mastersininnovation.com F P=? Area (A) Conventional mechanics: Pressure (P) = Force (F) / Area (A). In reality, when two surfaces are pressed together, interaction only takes place at the tips of the surface asperities. The area of contact between 2 elastically deformed bodies can be calculated using the Hertz theory. 12.10.2007 Slide 22 CONFIDENTIAL
  • 23. © VERHAERT SPACE Tribology & wear-out of mechanisms 4-Assess/analyse the wear aspects (5/6) Myth 4: “Friction and wear are related”. www.mastersininnovation.com High friction does not always mean that you get a higher wear (see plot) Specific wear rate (k) Friction coefficient 12.10.2007 Slide 23 CONFIDENTIAL
  • 24. © VERHAERT SPACE Tribology & wear-out of mechanisms 4-Assess/analyse the wear aspects (6/6) Myth 5: “ You always need large quantities of oil/grease to get good lubrication” www.mastersininnovation.com > No, small quantities are generally sufficient. > A certain amount of lubricant is usually in place for another reason: Removal of heat (e.g. car engine) Reserve for lubricant losses (e.g. leakage, evaporation, creep,…) Feel confident > On the other hand: too much lubricant can produce excessive heat & torque or power losses or even damage. 12.10.2007 Slide 24 CONFIDENTIAL
  • 25. © VERHAERT SPACE Tribology & wear-out of mechanisms 1. Select between wet and dry lubrication (working conditions). www.mastersininnovation.com 2. Avoid a poor design, operation/functioning of your mechanism. 3. Analyze/ assess contact loads/stresses, bending stresses, … 4. Assess/analyze the wear aspects/phenomenon. 5. Make final decision on tribological selection. 6. When possible/required: perform functional, friction/wear and life test. 12.10.2007 Slide 25 CONFIDENTIAL
  • 26. © VERHAERT SPACE Tribology & wear-out of mechanisms 5-Make final decision on tribological selection www.mastersininnovation.com Based upon the above: → Confirm initial selection wet <> dry lubrication → Detailed implementation & final selection 12.10.2007 Slide 26 CONFIDENTIAL
  • 27. © VERHAERT SPACE Tribology & wear-out of mechanisms 5-Make final decision on tribological solution 5.1- Liquid/ wet lubricant examples Type Tradename Vapour Pour Max. Viscosity Application www.mastersininnovation.com pressure point temp index ° ° (mbar at ASTM (°C) (°C) ° D2270 20°C) Perfluorinated Fomblin Z25 1.6E-13 -75 +250 358 Space mechanisms oils (Ausimont Italy) Perfluorinated Krytox 143AC 1E-6 -35 +285 134 Space mechanisms oils (Dupont US) MAC oil Pennzane SHFX2000 -48 +150 137 Space mechanisms Synthetic oil BP135 (BP UK) 1E-8 -57 +200 137 Space mechanisms ↑ Synthetic Rotella SAE 5W-40 -40 +220 176 Heavy duty diesel & gasoline engine ↑ Synthetic Aeroshell turbine -55 +250 105 Jet, helicopter and 500 industrial turbines ↑ Paraffinic + Shell S68 -37 +230 115 Rotary screw compressors additives + ammonia refrigeration 12.10.2007 Slide 27 CONFIDENTIAL
  • 28. © VERHAERT SPACE Tribology & wear-out of mechanisms 5-Make final decision on tribological solution 5.2- Solid/dry lubrication technology www.mastersininnovation.com 5.2.1 Self lubricating materials (polymers, bronzes…). 5.2.2 Surface treatments/coatings. 5.2.3 Ceramic materials. 5.2.4 Nano composite materials. 12.10.2007 Slide 28 CONFIDENTIAL
  • 29. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.1 Self lubricating materials (polymers). Polymer Density Tensile Wear Hardness Max. temp. TC CTE ° (kg/m³) strength particle (Shore D) (° C) (W/mK) (ppm/°C) (MPa) generation www.mastersininnovation.com PTFE, Teflon ® 1400 9 Good 50-65 280 0.23 90 Polyacetal 1400 5 Good 65 90 0.23 90 30% PTFE filled 1400 45 Good 60 100 - - acetal Polyamide, Vespel 1450 86 (SP1) Excellent 85 310 0.54 - ® 1600 59 (SP3) 80 Phenolic ® - 62 Poor 75 170 - 18-450 Torlon ® 1420 105 Excellent 50 to 90 270 0.26 31 Peek ™ 1500 97 Good 85 250 0.25 40 12.10.2007 Slide 29 CONFIDENTIAL
  • 30. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.1 Self lubricating materials (polymers). Phenolic material: application example. www.mastersininnovation.com We have successfully applied cotton-phenolic bearing cages in high-speed, lightly lubricated bearings (momentum wheel and motor applications). Phenolic also finds its way in industrial applications (e.g. SKF bearings, Barden US…). The lubricant we applied was Pennzane X2000, also the cage was oil impregnated. Advantages: • Low coefficient of friction • Ability to absorb lubricant • Dimensional stability in presence of lubricants/moisture • Good strength-to-weight ratio • Easily machined 12.10.2007 Slide 30 CONFIDENTIAL
  • 31. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.1 Self lubricating materials (bronzes). Cast bronzes are widely used because of combination of moderate to high strength, corrosion resistance, wear resistance and tribological behavior. Examples: www.mastersininnovation.com UNS number Name Composition Tensile Applications strength (MPa) C93700 (SAE 64) High lead tin 80% Cu, 10% 270 Bearings for high speed and heavy bronze (1) Sn, 10% Pb pressures, pump parts, pressure tight castings C90700 (SAE 65) Phosphor gear 90% Cu, 10% 305 Heavy duty gears, high load bronze Sn bearings, bushings and worm wheels C86300 (SAE430B) High strength 63% Cu, 820 Heavy duty high strength alloy for manganese 25%Zn, 3% Fe, gears, cams, slow speed heavy load bronze 6% Alu, 3%Mn bearings, screw down nuts C95400 (TQ00 Aluminium 85% Cu, 4%Fe, 620-700 High strength bearings, bushings, temper) bronze 11% Alu gears, worms, wear plates, valve seats and guides (1): Widely used for space applications (BB cage material + ion lead plated coating) 12.10.2007 Slide 31 CONFIDENTIAL
  • 32. © VERHAERT SPACE Tribology & wear-out of mechanisms 5-Make final decision on tribological solution 5.2- Solid/dry lubrication technology www.mastersininnovation.com 5.2.1 Self lubricating materials (polymers, bronzes…). 5.2.2 Surface treatments/coatings. 5.2.3 Ceramic materials. 5.2.4 Nano composite materials. 12.10.2007 Slide 32 CONFIDENTIAL
  • 33. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings (overview) Technology level www.mastersininnovation.com Physical Vapor Chemical Vapor Deposited (PVD) Deposited (CVD) Pulsed Plasma nitriding Laser cladding Dispersion coating Carburizing Nitriding Anodizing Induction/flame hardening Resin bonded coatings Process complexity Burnished films 12.10.2007 Slide 33 CONFIDENTIAL
  • 34. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings (thickness) Surface treatment depth Coating/treatment thickness www.mastersininnovation.com Nitriding/ carburizing Anodizing Ion implant Plasma spraying CVD PVD 12.10.2007 Slide 34 CONFIDENTIAL
  • 35. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings Burnished films www.mastersininnovation.com Application Application of lubricant film onto the surface (by hand e.g. brush or cloth) Layer Crude and difficult to achieve a good and constant layer thickness Life Short life (low duty). Lubricant Mostly MoS2/graphite based lubricants Applications - Low duty hinges and axes of various equipments - Corrosion & wear protection of low duty items 12.10.2007 Slide 35 CONFIDENTIAL
  • 36. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings Resin bonded coatings (1/2) “ lubricating paints” www.mastersininnovation.com Application Application of lubricant films, which are painted or sprayed onto the surface. They mostly require curing following application (can also be air cured). Layer About 1 micron. Not always easy to achieve a constant layer thickness. Life Moderate Lubricant MoS2, Teflon ® based, Silicon oils, Nickel 12.10.2007 Slide 36 CONFIDENTIAL
  • 37. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings Carburizing www.mastersininnovation.com Process Steel hardening. Involves the diffusion of carbon into the surface layers of a low carbon steel at high temperatures. Controlled cooling after carburising (water, oil or polymer quenching) produces hard martensitic layers at the surface. Purpose Increase hardness (wear resistance) and fatigue strength of generally low carbon steels Layer Materials can be hardened to about 650Hv whilst leaving the body relatively tough and fatigue resistant. Applications General low carbon steel hardening. Create hard and good adhesive layer for PVD/CVD coatings. Practically used on all automotive gearwheels. 12.10.2007 Slide 37 CONFIDENTIAL
  • 38. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings Nitriding www.mastersininnovation.com Process Steel hardening. Involves the diffusion of nitrogen into the surface layers at temperatures between 500 – and 570 °C Purpose Increase hardness (wear resistance) and fatigue strength of including cast iron, mild steel, tools, high speed and stainless steels. Layer Hardness <> layer thickness (see next slide) Applications General steel hardening and fatigue strength improvement Create hard and good adhesive layer for PVD/CVD coatings General machine parts, gears, extrusion worms, diesel injector bodies, crankshafts,… 12.10.2007 Slide 38 CONFIDENTIAL
  • 39. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings Pulsed plasma nitriding www.mastersininnovation.com Similar to traditional nitriding technology but with the following advantages: • Less risk to change the core properties of your material • Shorter process times (compared to traditional nitriding) • Better uniformity • Possible on complex geometries/surfaces • Eliminates costly cleaning or grinding to remove the brittle white layer associated with traditional nitriding. • Higher hardness than conventional nitriding (up to 1300 HV). 12.10.2007 Slide 39 CONFIDENTIAL
  • 40. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings Anodizing www.mastersininnovation.com Process Hard anodisation of aluminium alloys Purpose Increase surface hardness and/or abrasion resistance. Layer The thicknesses are usually between 25 and 250 µm (pending on the anodising time). Advantages Wear resistant - Low coefficient of friction – Anti-adhesion - High corrosion resistance – High chemical resistance - FDA compliance Applications Items and machine elements used in food industry (no extra lubricants). Extended hard anodize: TUFRAM ® > Aviation & non-magnetic bearings. > Automotive items, folding devices, pneumatics, medium load items. 12.10.2007 Slide 40 CONFIDENTIAL
  • 41. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings Ion implantation www.mastersininnovation.com Process Relatively low temperature PVD process Purpose Increase wear resistance, friction, fatigue life, corrosion and oxidation resistance. Typical implants C, Ni, O, Boron Layer thickness Typical 0.1 micron Advantages The process can be applied to virtually any material, including most metals, ceramics and polymers Niche application: Precision-tempered steel bearings: Advantage w.r.t. traditional coatings (even very thin layers) which can result in unacceptable dimensions and surface finish changes. 12.10.2007 Slide 41 CONFIDENTIAL
  • 42. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings Laser cladding www.mastersininnovation.com Process Similar to surface melting, but promotes alloying by injecting another material into the melt pool, using a laser. Purpose Achieve high-temperature performance, wear resistance, improved corrosion resistance, better mechanical properties… Typical implants Powder material, ceramics Layer thickness Strong metallurgical bond. Thickness from several hundred microns to several millimeters Post treatment Grinding and polishing generally required after coating Limitations • Unable to coat areas that are out of the line of sight. . • If the density is too high, cracking and delamination can occur as is the case with aluminum and some steels. Applications Machine parts, crank shafts, heavy industry parts 12.10.2007 Slide 42 CONFIDENTIAL
  • 43. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings Physical Vapor Chemical Vapor www.mastersininnovation.com Deposited (PVD) Deposited (CVD) PVD covers processes, such as: CVD covers processes, such as: • Sputtering • Atmospheric Pressure Chemical Vapour • Magnetron sputtering Deposition (APCVD) • Evaporation • Low Pressure Chemical Vapour • Ion plating Deposition (LPCVD) • Catodic arc deposition • Metal-Organic Chemical Vapour • Arc vaporisation Deposition (MOCVD) • Vapor ionisation (plasma) • Plasma Assisted Chemical Vapour Deposition (PACVD) • Plasma Enhanced Chemical Vapour Deposition (PECVD) • Laser Chemical Vapour Deposition (LCVD) · 12.10.2007 Slide 43 CONFIDENTIAL
  • 44. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings Physical Vapor Chemical Vapor www.mastersininnovation.com Deposited (PVD) Deposited (CVD) Pro’s: Pro’s: • Metallic & non-metallic • Metallic & non metallic (but less than PVD) • Can penetrate porous bodies, blind holes • Coatings are conformal & near net shape • High purity (99,99%) • Relatively low temperature • Material formations below melting point > No post re-hardening to be applied • Coatings are conformal & near net shape • Good for sharp edges (cutting tools) • Many parts can be coated simultanuously Con’s: Con’s: • Only coat area’s exposed to ion source: • Substrate to be heated (can loose hardening) not for deep holes > required post re-hardening • Most processes not for aluminium 12.10.2007 Slide 44 CONFIDENTIAL
  • 45. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings Physical Vapor Chemical Vapor Typical coatings Deposited (PVD) Deposited (CVD) www.mastersininnovation.com Material Hardness Typical application Titanium carbonitride TiCN 4000 High duty coating for polymer bearings (over 2 to 3 times tool life of TiC) Titanium carbide TiC Coating of 440C balls Titanium aluminium nitride TiAlN 2600 High temp drilling & tapping tools Titanium nitride TiN 2900 One of the oldest coatings in automotive, machine tools Chromium nitride CrN 1700-2500 Dies, heavy duty forming applications Zirconium nitride ZrN 2800-4600 Punches & cutting tools, blades Diamond like coating 1000-5000 (DLC) Tungsten carbide WC (W2C) 2400 Cutting tools, extreme high temperature use, dies, punches 12.10.2007 Slide 45 CONFIDENTIAL
  • 46. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.2 Surface treatments/coatings (PVD) Example: ion plated gearbox (Verhaert Space): www.mastersininnovation.com Main features/requirements (prime): • Planetary gear • Storage without maintenance: 1 year • In orbit standstill: 1 year • Input speed: 1662 rpm • Output speed: 3 (red. Ratio 554) • Output torque: 427Nm • Gear material: MP35N (Ftu=1800MPa; 545HV) • Bearing contact load: 2700MPa 80mm • Life requirement: 15 years in orbit • Weight: < 1.5kg 133mm 12.10.2007 Slide 46 CONFIDENTIAL
  • 47. © VERHAERT SPACE Tribology & wear-out of mechanisms 5-Make final decision on tribological solution 5.2- Solid/dry lubrication technology www.mastersininnovation.com 5.2.1 Self lubricating materials (polymers, bronzes…). 5.2.2 Surface treatments/coatings. 5.2.3 Ceramic materials. 5.2.4 Nano composite materials. 12.10.2007 Slide 47 CONFIDENTIAL
  • 48. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.3 Ceramic materials Pro’s: www.mastersininnovation.com • High hardness (limited wear) • High youngs modulus (increase mechanism stiffness) • Chemically inert • Relative low density • High temperature allowed • Non magnetic Con’s: [Toyota full ceramic diesel engine • Thermal mismatch with steel turbo charger] • Low (limited) tensile strength > cracking • Soft preloading to be applied in case of thermal mismatch (CTE) • Boundary lubrication can be required (pump bearings) 12.10.2007 Slide 48 CONFIDENTIAL
  • 49. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.3 Ceramic materials (properties <> steel) Aspects/property Bearing Ceramics Remark steel (Si3N4) www.mastersininnovation.com Density (kg/m³) 7800 3200 Lowers centrifugal force: allows high spindle speeds in machines up to 35000 RPM ° 180 800 Maintains stability @ high temperature Allowable temp.(°C) CTE (ppm/ °C) 12.5 2.9- 3,2 Minimum deformation but thermal mismatch with steel > cracks possible in hard preloaded systems Hardness (HV) 700 to 1400 to Reduced ball/race contact in ball bearings; less 800 1700 wear Young's mod (GPa) 190-210 310 Less embedding & contact Magnetic Ferromag Non Reduced torque in magnetic fields netic magnetic Corrosion Poor- OK Excellent Less wear; allows harsh environment; longer resistance (pending life on steel) 12.10.2007 Slide 49 CONFIDENTIAL
  • 50. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.3 Ceramic materials (typical application examples) Milling machines [1]: Ceramic bearings allow speeds up to 30000 RPM (25% ↑ www.mastersininnovation.com w.r.t. steel bearings) with a life increase of also 25%. These use full cermaic bearings of SiN4 (better than ZrO2), where the cage is PTFE, PEEK or phenolic. Helicopters [2]: Use through hardened stainless steel bearings with ceramic coating of the races; the ball separator is made from PTFE/glass composite (10X improved life w.r.t. full steel bearings using a liquid lubricant. [1]: Example: IBAG North America [2]: Reported by Ampep, SKF aero-space 12.10.2007 Slide 50 CONFIDENTIAL
  • 51. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.3 Ceramic materials (bearing technology) Ceramic hybrid bearings: www.mastersininnovation.com These use ceramic balls (SiN, Al2O3 or Zr) on steel races. Advantages w.r.t. full steel bearings: • 40 % lighter than steel • Three times stronger (load capability) • Can run up to 4 times longer (SKF) • Better corrosion resistance • Less microwelding (vacuum applications) • Less friction > bearings will run cooler • Higher stiffness, more accuracy > smoother running & less vibrations 12.10.2007 Slide 51 CONFIDENTIAL
  • 52. © VERHAERT SPACE Tribology & wear-out of mechanisms 5-Make final decision on tribological solution 5.2- Solid/dry lubrication technology www.mastersininnovation.com 5.2.1 Self lubricating materials (polymers, bronzes…). 5.2.2 Surface treatments/coatings. 5.2.3 Ceramic materials. 5.2.4 Nano composite materials. 12.10.2007 Slide 52 CONFIDENTIAL
  • 53. © VERHAERT SPACE Tribology & wear-out of mechanisms 5.2.4 Nano composite materials What are nanocomposites? www.mastersininnovation.com • Material particles (of various constituent materials) mixed at the nanometre scale (in matrix form). How to create: • PVD & CVD like processes > relatively expensive. • Electro deposition (electrolysis) > nowadays cheapest • Still in it’s infancy Nanomaterials to support many applictions: > http://www.qinetiq.com/home_nano/products.html QinetiQ Nanomaterials Ltd (QNL) is Europe's leading manufacturer and supplier of nanopowders and related technical services, providing a wide range of nanometric products to an international client base. 12.10.2007 Slide 53 CONFIDENTIAL
  • 54. © VERHAERT SPACE Tribology & wear-out of mechanisms 1. Select between wet and dry lubrication (working conditions). www.mastersininnovation.com 2. Avoid a poor design, operation/functioning of your mechanism. 3. Analyze/ assess contact loads/stresses, bending stresses, … 4. Assess/analyze the wear aspects/phenomenon. 5. Make final decision on lubrication/ technology/ materials. 6. Performance of functional, friction/wear and life test. 12.10.2007 Slide 54 CONFIDENTIAL
  • 55. © VERHAERT SPACE Tribology & wear-out of mechanisms 6-Functional/friction/wear and life test (1/4) Overview of test/inspection www.mastersininnovation.com We perform the following test/inspection (space applications): → Dedicated friction/wear test → Functional performance test in the applicable environment, like: → operating regime → temperature & pressure → loading → running-in test → Life test → Strip down and microscopic inspection 12.10.2007 Slide 55 CONFIDENTIAL
  • 56. © VERHAERT SPACE Tribology & wear-out of mechanisms 6-Functional/friction/wear and life test (2/4) Running in of a mechanism www.mastersininnovation.com Typical friction profile in time as the basis to perform running-in. Selection of running-in cycles and load: based on experience and above plot. 12.10.2007 Slide 56 CONFIDENTIAL
  • 57. © VERHAERT SPACE Tribology & wear-out of mechanisms 6-Functional/friction/wear and life test (3/4) Example: running in of a gearbox www.mastersininnovation.com 0.05 0.04 0.03 0.02 0.01 0 0 20 40 60 80 100 Typical friction profile per cycle Friction profile in time 12.10.2007 Slide 57 CONFIDENTIAL
  • 58. © VERHAERT SPACE Tribology & wear-out of mechanisms 6-Functional/friction/wear and life test (4/4) Friction and wear test www.mastersininnovation.com Tribometer: pin on disc method is used to characterise friction & wear. 12.10.2007 Slide 58 CONFIDENTIAL
  • 59. © VERHAERT SPACE Tribology & wear-out of mechanisms www.mastersininnovation.com Verhaert New Products & Services nv Hogenakkerhoekstraat 21 9150 Kruibeke Belgium Tel +32 (0)3 250 19 00 Fax +32 (0)3 254 10 08 www.verhaert.com info@verhaert.com www.mastersininnovation.com 12.10.2007 Slide 59 CONFIDENTIAL