The use of Keronite surface treatment technology in the automotive industry

Transcription

1 The use of Keronite surface treatment technology in the automotive industry Lars Olrik Keronite International Ltd 2006 International Conference on GREEN SURFACING TECHNOLOGY 18 July 2006

2 The Keronite mission Our mission is clear Keronite is a world leader in the provision of technology services to industry, enabling manufacturers in many sectors to reduce costs and improve efficiency through the use of light metals such as aluminium and magnesium SOLUTIONS + APPLICATIONS + HARDWARE

3 What is Keronite? Advanced surface treatment for aluminium, magnesium and titanium alloys to provide superior hardness, wear, corrosion and thermal resistance Worldwide patented plasma electrolytic oxidation process (PEO) A user-friendly and non-toxic process Proven industrial technology Variety of applications

4 The Keronite process Keronite electrolyte contains no heavy metals, Cr, acids, ammonia Low concentration alkali is easily disposed

5 The Keronite process Keronite is produced by transforming the substrate metal surface into a hard, dense and adhesive oxide layer by plasma discharge in a liquid electrolyte

6 Keronite cross section Keronite coating consists of three major parts: Thin intermediate layer provides atomic bond between metal and ceramic Functional layer of fused ceramics, provides hardness and wear resistance Top porous layer (5-25% of total) perfect base for top coats (e.g paint, lacquer, PTFE, metal)

7 Surface morphology Keronite is different from anodising: Keronite uses electrical pulses of both positive and negative polarities Keronite creates controlled plasma discharge on the surface of treated parts As a result, surface plasma discharge fuses metal oxide into a harder phase SEM images of surfaces of the Keronite and anodised Mg 10 microns thick

8 Keronite properties

9 Hardness KERONITE on Aluminium Hard Chrome Hardened Tool Steel Hard Anodized Aluminium 304 Stainless Steel Mild Steel Aluminium Up to 2,000 HV on aluminium Up to 700 HV on magnesium Comparative Hardness (HV)

10 Hardness Vickers hardness measured by Corus 30 µm Keronite + PTFE on 2219 aluminium alloy distance HV 0,05 from edge [µm]

11 Galvanic corrosion resistance AZ91D Mg samples were fastened with a zinc plated and TriPass EVL 1000-M10x50 mm steel bolt and tightened to 5 Nm, and subjected to cyclic corrosion test GM9540P: 80 cycles Coupons weighed before and after to 4 decimal places Percentage weight loss recorded Source: MacDermid plc.

12 Galvanic corrosion resistance Results of the cyclic corrosion test GM9540P expressed as a percentage weight loss Finish on Mg Bolt % weight loss Appearance on Mg None No 1.5% Pitted, white corrosion None Yes 4.0% Pitted, extensive corrosion Keronite +JS500 No < 0.1% No change Keronite +JS500 Yes < 0.1% No change Mg Mg/steel bolt K+JS500 K+JS500/steel bolt Source: MacDermid plc.

13 Corrosion resistance on magnesium Material: cast AZ91D alloy Tests: salt spray, galvanic, scribe, paint adhesion to automotive customer s own formulation 100% Aggregate corrosion resistance score 99% 80% 75% 60% 53% 40% 20% 0% Chrome-free Chromate Keronite

14 Good thermal barrier % Al 6061 Al5Si Al12Si Al17Si4Cu α-al2o3 Keronite Thermal conductivity (W/m/K) Keronite amorphous/multi-crystalline structure inhibits phonon transport Stable up to 800ºC

15 Tribological properties On aluminium Keronite can be used to give High friction: µ > 0.6 maximum for e.g brakes or clutches Low friction: µ = 0.04 minimum after polishing with latest generation Keronite for sliding, bearing oil-filled applications F N µ F = µn

16 Wear resistance The wear resistance of Keronite has been evaluated by the pin-on-disk method and compared with the wear resistance of hard anodic coating (Mil-C-8625 type 3) and of 5140 steel 50 HRC Testing procedure: Pin samples: Flat ring samples with a diameter of 20 mm Disk medium: Abrasive paper P320 Sliding velocity: 0.35 mm/sec Contact pressure: 0.08 MPa Wear was measured by weight loss per sliding distance: (mg/m) Results and discussion: Keronite 0.14 Hard Anodic coating 0.55 Steel 5140 (50HRC) 1.47 Conclusion: Keronite coating had wear resistance about 4 times higher than hard anodising and over ten times higher than 5140 steel

17 Composite coatings Controlled porous structure of Keronite is ideal for: oil retention in powertrain applications OR adhesion of secondary materials for dry lubrication (e.g. PTFE) or added wear resistance (chemical nickel)

18 Coating on inner thread of M4 bolt hole Throwing power

19 Edge integrity Uniform and predictable thickness From 10 to 150 microns Can be polished Complex shapes can be treated SEM back scattered image showing an edge of hard anodised coating on AA7075 alloy. SEM back scattered image showing an edge of the Keronite coating on AA7075 alloy.

20 Flexibility 100µm detached Keronite film showing ability to be bent or flattened elastically In more severe deformation, both plastic and elastic deformation occurs before failure 1cm Courtesy of Cambridge University Flexibility gives the coating resilience against small impacts or deformation of the substrate. Avoids cracking in-service

21 Magnesium Applications

22 Magnesium applications Corrosion protection Keronite on magnesium body and engine parts BMW,VW approvals

23 Magnesium applications Approved for US military use on magnesium gearbox casings Keronite + Rockhard epoxy topcoat system Production 2006 Allison Transmission Allison Transmission Division of General Motors

24 Magnesium applications Magnesium pistons Keronite prevents skirt wear and pin-hole wear Under investigation in Japan, Europe and USA

25 Magnesium applications EU Nanomag project 3yr study into environmentally-friendly coatings for Mg anti-corrosion and wear in the transport industry Included tribology study of Al c.f. Keronite + Mg 4 different tests (pin-on-disk, ball-ondisk, sliding wear of piston, rotating wear of piston pin) to assess the tribological behaviour of Keronite on Mg Cylinder liner (AlSi alloy) Piston section Load:100N; Frecuency: 20Hz; Stroke: 3mm; Time: 30 minutes; Temperature: 150ºC Oil: Repsol 15w40 Used

26 Magnesium applications Nanomag piston-cylinder tribology results Friction Coefficient 0,5 0,4 0,3 0,2 0,1 0 Magnesium Time (s) mg Am Cylinder piston wear Am Piston cylinder wear Aluminium Magnesium Magnesium Magnesium Al Mg Mg+K1 Mg+K2 Experimental Standard coating coating Piston material

27 Aluminium applications

28 Piston crowns Keronite surface resists detonation damage: Allows higher specific power and leaner burn Resists flame quenching on crown Reduces piston temp. Does not peel or crack Won WRC rally race. Can coat diesel piston bowl Locomotive engine ran for 7 years with no deterioration to crown coating Temperature C Thermal Barrier Test KERONITE on Al (400 C) Time (minutes) Heater Plate Uncoated KERONITE 40 mkm

29 Gasoline piston top ring groove Issue Wear of top ring groove during engine life Keronite surface Approx HV (c.f Hard anodising HV), Ra<1µm Approx. five times less system wear than hard anodising Reduced wear means lower emissions and blow-by Allows smaller land height hence lower unburnt HC emissions Very thin layer better cooling and cost competitive 3.5±1µm 4.4±1.5µm

30 Top groove wear results 1.8l I4 16V NA gasoline engine 100 hour dyno test cycling between max power and max torque Aluminium (ADC12) piston Nitrided steel ring 15µm Hard anodising 5µm Keronite Max wear on top groove 10µm 0.5µm Max wear on ring 0.5µm 2µm Total wear c10µm c2.5µm

31 Densitometry and porosimetry Cumulative Cummulative pore volume volume (ml/g) (ml/g) Inter-flake porosity Pore diameter (nm) Intra-flake porosity 10 Pore diameter (nm) Nano-scale porosity is believed to be responsible for good oil retention Porosity (% from cut-off) Porosity (%) FEGSEM Surface 0.5 μm Crystallographic density 3.7±0.2 g cm -3 Skeletal density ~ 3.7 g cm -3 (Archimedes, He, Hg) Bulk density ~ 3 g cm -3 Surface area ~ 4 m 2 g -1 (BET) Porosity ~ 20% (Hg porosimetry, BET, skeletal density) Source: Cambridge University

32 Conclusions Enabling technology for light alloys (light weight means less fuel consumption) Keronite coated engine parts can exhibit very low friction (down to µ=0.04) for increased fuel economy Keronite coated engine parts have increased durability which allows engines to be tuned more efficiently Non-toxic electrolytic process no heavy metals, Cr, acids, ammonia - easily disposed No heavy metals means coated parts can be recycled Damaged or worn parts can be re-coated without stripping. Allows re-use rather than scrap policy

33 Thank you! Mg closures Mg fender Mg roof brackets Master cylinder Mg intake x fold Roof bars Cylinder liner Valvetrain Mg rocker cover Cylinder head Mg hood Park brake Brake rotor Al brake piston Al strut Mg Wheel Mg door inner Clutch ring Piston Diesel pump Mg FEM Mg Housings Transmission case FEAD pulleys Transmission plate