Lecture 18:Applications

IntroductionMain Benefits of Applying Hard coatings onto machine parts•High hardness•Improved oxidation resistance•Chemical inertness•Improved corrosion resistance•Low Friction•Increased Wear life

Unique combination of bulk material properties and coating propertiesExample: High toughness of bulk + high hardness of coating,

Hybrid Coating SystemsUnique combination of different coating processes

(Marco defect free dense coatings –E.g. Arc-Magnetron Sputtering)

ResultsBetter coatings, higher performance on

coated parts, reduced overall cost

Application Areas

Thin Film Coating(PVD, CVD)

Cutting Tools

Automotive IndustryOptical Applications

BiomaterialsMicro Electronics,MEMS

Decorative Coatings

Cutting Tools• High tool surface hardness• High tool life and performance• Low tool change requirements• Good surface finishing of work piece

Drawing operation, 302SS with water soluble lubricant. Uncoated M4 tool required polishing after 1000 parts. TiN coated tool required polishing after 8,000 parts.

Forming operation, brass doorknobs. Uncoated tool produced 20,000 parts before maintenance. TiN coated tool produced 100,000 parts

Automobile Engine Parts• Coating of engine parts improves horsepower and provide longer engine life. • Thermal Barrier Coating to the piston’s combustion face :

– maintain combustion temperatures – prevent heat soak to the rings

• Lubricious dry film coating on the skirt: – reduces friction – prevents scuffing and galling of the cylinders– decrease wear of engine parts

• Reduced fuel consumption by reducing friction• Reduces emissions by enabling higher pressure fuel injection

Door Lock

Various Gears

Current and Potential Energy Saving Applications of Me-DLC Coatings

CamsTappets

Valves

PistonsPiston Rings

Crankshaft

Fraunhofer Institute

Current automotive components• Camshafts, crankshafts, pistons,piston rings, tappets / shims,gears, bearings, valves,plungers (diesel injection)• Increasing wear resistance• Decreasing frictionTargets:- Reduce energy consumptionimproved fuel efficiencyreduction of the CO2-emission- Power amplification (Car Racing)better acceleration

CrN-coatedTappets

Volume of Applications for Various Coatings

Hauzer Techno Coating

DLC-CoatedPiston Pin CrN-Coated

Piston Rings

DLC-coated Fuel Injector Plungers

Thermal Barrier CoatingsThermal Barrier Coatings (TBC) are used to protect the substrate from severe temperature and chemical environments.

Thermal Barrier Coatings are typically ceramic composites based on

Zirconia, Alumina, Titanium

High hardness, wear resistance and good chemical stability make TBC very desirable in cutting tool applications

Applications:• Cutting tools: High speed cutting in poor

cooling conditions• Tribune Blades: High temperature

condition of air craft engines– In aircraft engines temperatures generally

exceed 2600°F. – 300°F improvement in the temperature

capability with TBC in aircraft engine parts– increase in the properties such as oxidation

and creep resistance and thermal mechanical failure, of the blades

– The low thermal conductivity of ceramics provides thermal insulation to the high temperature combustion gages present in the engine

• Molds working in high temperature:Glass, aluminum, plastic extrusion etc.

Thermal Barrier Coatings (Continued…)

Schematic of the structure of a two layer thermal barrier coating on a turbine blade surface together with a temperature profile

In ship diesel engines only 30-40% of the chemical energy contained in the fuel are converted into useful power. The rest of the energy are heat losses to exhaust gas and engine cooling by water and oil *.

* Combustion Engines, Interfacial Engineering of Materials, Il Ciocco, Toscana, Italy, 9.-14.10.96 (1996)

Magnetic storage technology

OVERCOAT

DISKHEAD

Filtered Arc-PVD CNxSputtered DLC

Nano-wearresistance

Flying Head

Anti-Fogging and Hygienic Coatings

TiO2 coated tiles in an hospital environment showed the surface bacteria on the wall surfaces were reduced to zero, plus airborne bacteria counts were reduced.

Anti-fogging glassGenerally is moist air comes in contact with glass, small droplets of water are formed, and the glass becomes fogged. On TiO2 coated glass, the water forms a continuous flat sheet, so that there is no fogging.

Areas of activity in TiO2 photocatalysis1 fog proof, and self cleaning glass2 anti-bacterial, anti-viral, fungicidal3 anti-soiling, self cleaning 4 deodorizing, air purification5 water treatment, water purification

Micro Electronic Devices

Basic Structure of the enhancement MOSFET

SEM micrograph of the rf-SET displacement detector(Miles Blencowe, Physics Reports 395 (2004) 159–222)

MEMS

The cross-sectional diagram (a) and SEM picture (b) of a Ni cantilever cut from an electroplated Ni film plate, and released by etching in KOH solution (*)

* J. K. Luo, A. J. Flewitt, S. M. Spearing, N. A. Fleck and W. I. Milne, Volume 58, Issues 17-18 , 1 July 2004, Pages 2306-2309** J. -M. Huang, A. Q. Liu, Z. L. Deng, Q. X. Zhang, J. Ahn and A. Asundi, Sensors and Actuators A: Physical, In Press, 7 June 2004

The SEM graph of the torsional micro-mirror (**)

Potential Applications:Pressure and flow sensorsAccelerometersMicro actuatorsMicro fluidic componentsPrecision structures for optical devices

Microelectromechanical Systems, MEMS

From Argonne

20 µm

cantilever Turbine

Comb drives

Gears

300 µm

Single Level Amorphous Diamond MEMS Structures*

30 µm

J. P. Sullivan, T. A. Friedmann, and K. Hjort, Mat. Res. Soc. Bull. 26 (2001) 309.*Courtesy of Tom Friedmann

Sandia National LaboratoriesNanostructure PhysicsT.A. Friedmann 2000 Sandia National Laboratories

Material Properties•70% sp3 carbon•atomically smooth•Hard ~85 GPa•10,000 times the wear rate of Si

•stress-free film

Dental Applications

TiN Coated Dental Implants and3-Blade Cutting Edges

Bio-Medical ImplantsBio-compatible and wear resistant coatings for Hip-Joint Implants

Synthesis and Production of NFC on Select Medical Devices

SS Catheter

NFC-coated SS Catheter

NFC-CoatedFemoral

Head

NFC-coatedMandibularHead

UHMWPE Acetabular

cup

Head and cupare together

NFC-coated Ceramic

Head

Coronary StentsCoating a coronary stent with advanced ceramic materials with coatings having

a low wettability and a low piastrinic adhesion

e.g. TiC, TaC, TiN, TaN and DLC coatings with minimal inflammatory reactivity toward tissues and the absence of toxic and carcinogenic effects

• Titanium-Nitride-Oxide (TiNOX) coated stentis used in the treatment of de novo lesions in patients with single or multivessel coronary artery disease

• TiNOX-coated stentssignificantly reduces the restenosis rate

Coronary Artery

Stent Lesion

Drug Delivery Coatings for StentsWithout a coating,

red blood cells will attach to medical devices, forming a clot on the surface

When in contact with blood, the drug delivery polymer coatingreleases entrapped heparin inhibiting platelet adhesion and clotting protein activation

Optical CoatingsDepositing single or multiple layers of metallic and/or dielectric materials, with different reflactive index and with thickness, it is possible to modify the spectralcharacteristics (reflection, trasmission and polarization) of the material.

Examples for these coatings: TiO2, SiO2, Ta2O5, ZrO2, Nb2O5, CeO2, WO3, LaF3, MgF2

Coatings for Optical Filters and Lenses

These pictures were taken with a standard camera lens.

These pictures were taken with the samelens and the addition of an AR Coated Filter.

Optical coatings reduce reflection both internally and externally and thereby increase the amount of light that reaches the eye which improves brightness and contrast.

Coated lens surfaces improve light transmission capability

Decorative CoatingsBath/kitchen/door hard ware,watches, spectacle frames

Multicomponent, Multilayer (µm)Coatingarchitecture

(II) • Achievement of various surface properties• Mismatch reduction between coating and substrate• Strain and stress control within the film• Reduction of crack propagation• Hardness and toughness enhancement

Courtesy of Seco Tools

Austenitic stainless steelTiC : enhanced adhesion

Al2O3 : wear resistance at elevated temperature

Ti(CN) : low sticking + wear indicatorMultilayered hard coating

Gilmore 98 Goller 99

TiB2-MoS2

TiB2-C

C or MoS2 %

µ µ

TiN-MoS2

TiN

Multicomponent hard+soft coating

Gradient, nanostructured, superlatticeCoatingarchitecture

(III) • Major improvement in coatings technology for < 10 years• How to maximize H/E ? “elastic strain to failure”• Hardness, Toughness and Wear resistance increase• Limitation : T-induced phase transformations & diffusion• Tribological behavior / mechanisms : still open questions …

• Obstruction of dislocation glideand crack propagation

• Grain boundary sliding

Historical concept Veprek 95 Schiotz 01

Nanocomposites• nc-metal nitride / metal Musil 99• nc-metal nitride / a-nitride (silicide) Veprek 99• nc TI-B-N system Mitterer 98, Rebholz 98• nc-metal carbide / a-C Voevodin 97-99

Zhang 03 (Review)

Barnett 03

Superlattice Barnett 03, Münz 03 (Reviews)

… after annealing at 1000°C / 1h… no hardness decrease

Adaptative & smart coatingsCoatingarchitecture

(IV)

Voevodin 02

Self-adjustment of YSZ/Au/MoS2/DLC vs. Temperature & Environment

• Concept of adaptative coatings = f (temperature, environment, pressure)• Smart = adaptative + reversible

TiAlN + Y, Cr : friction-induced oxide formation Savan 99WC/DLC/WS2 : cycled air / vacuum friction Voevodin 99,00CaF2/WS2 : friction-induced CaSO4 formation at high T John 98MoS2 or WS2 / ZnO or PbO : friction induced PbMO2 or ZnWO4 Walck 97

General conclusion

It seldom pays to coat existing components

A total tribological approach should be adopted

including

Design

Materials selection and treatment

Surface finishing and treatment

Coating selection and application

Lubrication

Present Applications and Future Prospects for Diamond Coatings

• Thermal Management • Cutting Tools• Wear Resistant Coatings• Optics• Electronic Devices• Composite Materials

Cutting performancewhile machining a cast aluminum

alloy containing 7% Si

0

20

40

60

80

100

120

140

160

Num

ber o

f Wor

kpie

ces

per E

dge

Uncoated Insert CVD Diamond CoatedInsert

Condition of cutting edges after machining a cast aluminum alloy

Uncoated NanocrystallineDiamond Coated

Tribological Functional CoatingsMain Benefits of

Applying Hard coatings onto machine parts

• High hardness• Improved oxidation

resistance• Chemical inertness• Improved corrosion

resistance• Low Friction• Increased Wear life

Unique combination of bulk material properties and coating propertiesExample: High toughness of bulk + high hardness of coating,

MB.34 (9801) e

Trends in mechanical engineering

• higher loads• smaller tolerances• less lubricants

Hard Coatings for Various Tribological Applications

Deposition Technique- Coating

Deposition Temperature (C)

Hardness Range (GPa)

Typical Friction Values

Major Applications

Desired Properties/ Requirements

CVD-TiN TiC, Al2O3, WC, Diamond

600-1000 15-90 0.05-0.5 Metal-cutting and forming, seals

High chemical Thermal resistance, high hardness and thoughness, strong adhesion, low chemical solubility in SS material

PVD-TiN TiC, TiCN, TiAlN, CrN, CrC, DLC, WC/C, MoS2

Room temperature - 600

0.6-40 0.003 – 0.5 Metal-cutting and forming, automotive, machine elements, etc.

High fatigue resistance, high-hot hardness, and non-stick properties in the case of metal forming;

Pulsed-laser, ion-beam-assisted, etc. – Oxides, some nitrides, MoS2, etc.

Sub-zero to 500

1-50 0.1-0.5 Mostly for research purposes, no major industrial applications

Low friction and high resistance to scuffing; ability to prevent substrate deformation