“PVD coatings in transmissions: case studies”

”I rivestimenti PVD su componenti di trasmissioni: esempi”

Paola Recanati – Oerlikon Balzers Italy- Precision Components Product Manager

Claudio Torrelli – Oerlikon Graziano – Head of Product Development

Agenda

1 Oerlikon – Company overview

2 The tribosystem

3 Surface engineering

4 PVD coatings

5 Application-tailored solutions

6 Gears, general

7 Case Study #1: Metallic sealing in off-road transmission

8 Case Study #2: Sports car gearbox

9 Case Study #3: Agricultural windrower

10 Case Study #4: IC engine piston pin

11 Case Study #5: Truck rear axle gear

12 Case Study #6: Differential pins

SegmentManmade Fibres

SegmentDrive Systems

SegmentSurface Solutions

SegmentVacuum

Company Overview – Four core competencies

The tribosystem

A tribosystem consists of many influencing parameters. Wear lifetime prediction is therefore difficult and based on specific trials and experience.

Pressure

Motion

Component # 1

Component # 2

Surrounding influences

� Temperature

� Relative humidity

� Pressure

Intermediate materials

� Oil

� Grease

� Water

� Particles

� Contaminants

Roughness

Typical failure modes

Abrasive wear

Cause

� Cold welding with material transfer

Adhesive wear

Cause

Surface fatigue (pitting)

Cause

� Material fatigue with crack formation by dynamic or cyclic load

� Hard particles score the surface

Surface Engineering

Methods of coating deposition

Coating

thermal

• welding• sintering• melting• dipping• …

mechanical

• roll cladding• explosive cladding• peening• …

mechanical-thermal

• flame spraying• plasma spraying• high-speed plasma spraying• …

vapor deposition

• Chemical Vapor Deposition

• Plasma Assisted CVD• Physical Vapor Deposition electrochemical

• chrom plating• nickel plating• zinc plating• anodizing• …

chemical

• electroless nickel plating• phosphatizing• chromization• sol-gel technique• …

Substrate

(0.001 µµµµm … 10 mm)

Coating portfolio

Nitriding Galvanic

Abrasion resistance

(Hardness)

Hard metal

Ceramic

Bronze

WC/C

DLC

CNI

DLC STAR (Sliding

performance)

CNI Temperature

CNI thick: Corrosion

CrC

CrC: Sliding &

Temperature

Seizure protection

(friction coeff.)

Coating main clusters

Carbon Coatings

BALINIT C/DLC/DLCS as examples

Typical hardness: 1000-2500HV

Typical friction coefficient: 0,1-0,2

Nitride Coatings

BALINIT A/CNI/AP as examples

Typical hardness: 1800-3200HV

Typical friction coefficient: 0,2-0,5

DLC sp2 & sp3Graphite sp2Diamond sp3

Metals: Ti, Cr, Al Non metals: C, N, B

Carbon Coatings - Dry running properties

BALINIT® C (WC/C) shows under dry running condition the lowest friction and highest wear life time compared to conventional surface treatments.

Coefficient of friction

Sliding distance [m]

X End of test due to adhesive wear

0.8

0.6

0.2

0.4

00 100 300200 400

AISI 52100 (DIN

1.3505), uncoated

AISI 4140 (DIN

1.7225), nitrided

Hard chrome

plated

BALINIT® C

(WC/C)

nearly no wear

x

xx

Structure of the BALINIT® C – Coating

Total coating structure WC/C-Section

WC/C- coating

Substrate material

Cr-interlayer

WC-coating

White lamella: WC-rich

Black lamella: C-rich

0.1 µm

Dual coating system BALINIT® DLC STAR

«STAR» versions of BALINIT® C or DLC, have a CrN layer underneath. This CrN is very ductile and gives excellent support properties, e.g. in cyclic loaded contacts like diesel injector needles.

DLC for low friction andwear resistance

CrN coating foradditional support

Base material forcomponent strength

Fields of application for BALINIT® coatings

Engines

Racing

Diesel injection pumps

Mobile phone

Leisure & Domestic Applications

Machine tools

Printing & Packaging

Watches

AerospaceCompres-sors

Precision Mechanics

Guns

Roller bearings

Gears

Hydraulics

Textile machines

Oil & Gas

Motorcycle

Medical Instruments

Medical Devices

Highly loaded fast running gear

Tooth flank stress [N/mm2]

BALINIT® C (WC/C) increases load carrying capacity (fatigue endurance limit) of case hardened gears by 10-15%. The reason is the reduced hertzian stress due to lowering of the friction and running in of the coating.

Stress cycles

2 24 6 8 107 2 4 6 8 108

2100

2000

1900

1800

1700

1600

1500

Test method:FZG-C-testcase hardened steel, 62 HRC, RZ = 3 µm

Uncoated

BALINIT®

C (WC/C)

Case studies

Case Study #1: Metallic sealing in off-road transmission

Case Study #2: Sports car gearbox

Case Study #3: Agricultural windrower

Case Study #4: IC engine piston pin

Case Study #5: Truck rear axle gear

Case Study #6: Differential pins

TurningRotary valve

Fix Housing

Main function = Sealing between outer and inner area

Max. pressure difference: 450 bar

Case study #1: Metallic sealing

Compact wheel loader transmission

Confidential

Shim fixed in the rotary valve

Counter piece: Valve block

Surface grinded and lapped

Case study #1: Metallic sealing

Compact wheel loader transmission

Confidential

Contamination of

• pump

• high pressure hoses

• tank

• filter

Replace of

• transmission

• pump

• filter

Cleaning of

• hoses

• tank (150l)

Estimated total cost app. 10K€

Case study #1: Metallic sealing

Compact wheel loader transmission

BALINIT® C guarantees the sealing functions and prevents/prolongs very difficult and expensive maintenance operations.

Confidential

Case study #2: Aston Martin Lagonda One-77

Coating of the cylindrical & bevel gears

One-77 is the high performance version of AML Vanquish

580Nm (510 HP) 750Nm (750 HP)

Gears contact stress is the gearbox limit to the increase of performances.

Due to development time constraint it wasn’t possible to develop a dedicated new gearbox

Case study #2: Aston Martin Lagonda One-77

Coating of the cylindrical & bevel gears

Test stopped

@ 200% lifetime

BALINIT® C increased the resistance to contact stress, doubling the life of the bevel set pinion.

Similar results were obtained on cylindrical gears.

Case Study #3: Torque Hub ® final drive windrower

BALINIT® C2VLT doubled life of sun gears

Case Study #4: Piston pins

BALINIT® DLC reduces the power consumption of the truck engine up to 600 W. DLC coating of wrist pins is also used to substitute the bronze bushing.

Engine speed [Rev/min]

Cylinder peak pressureReduction of power consumption [W]

0

100

200

300

400

500

600

700

2400200016002000800

115 bar

155 bar

90 bar

45 bar

135 bar

65 bar

Specification example (Diesel engine, no bushings)

Coating a-C:H on CrN support layer

Coating Thickness

2.5 ± 0.7 µm

a-C:H ≥ 0.8 µm (1.2 µm nominal)Process PVD/PACVDFilm Hardness ≥ 24 Gpa

Adhesion HF 1 – 4 (VDI 3198)Roughness Ra before / after coating 0.05 / 0.07

adhesion layer (e. g. Cr)

tough / ductile functional and / or support

layer (e. g. CrN)

hard functional layer with low friction and

low adhesion tendency (e. g. a-C:H)

intermediate layer or functional layer with

low friction (e. g. CrC/a-C:H)

substrate

Case Study #4: Piston pins

Typical “wear” at areas with

• highest load (edges con-rod)

• lowest lubrication (piston periphery)

• highest temperature (piston periphery)

• “wear” stops (intentionally) at interfaceto CrN – support-layer

Case Study #4: Piston pins

Case Study #5: Truck rear axle gear

0.0

0.2

0.4

0.6

0.8

1.0

110100908070605040

Bevel gears of vehicle axes have a rather high sliding ratio. This causes frictional losses.

BALINIT® C (WC/C) coating of a truck rear axle gear reduced frictional losses by 1.5 kW.

rear axle power loss due to splash and oil quality in function ofoil temperature. Axle type = U177E; ratio = 2.93; 1100 rpm

Power [kW]

Oil Temperature [°C]

Case Study #6: Differential pins

Differential for Combine Agricultural transmission.

BALINIT® C (WC/C) coatings could be used to replace bronze bushings between the pins and the planet gears