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“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