The use of Keronite surface treatment technology in the automotive

Transcription

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
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
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
The Keronite process
Keronite electrolyte contains no heavy metals, Cr, acids, ammonia
Low concentration alkali is easily disposed
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
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)
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
Keronite properties
Hardness
Up to 2,000 HV on aluminium
Up to 700 HV on magnesium
Comparative Hardness (HV)
KERONITE™ on Aluminium
Hard Chrome
Hardened Tool Steel
Hard Anodized Aluminium
304 Stainless Steel
M ild Steel
Aluminium
0
500
1000
1500
2000
2500
Hardness
Vickers hardness measured by Corus
30 µm Keronite + PTFE on 2219 aluminium alloy
distance
from edge
[µm]
20
75
125
175
225
275
325
375
425
HV 0,05
2143.0
55.2
51.7
56.1
55.3
58.5
56.1
60.3
63.9
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.
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
4
3.5
3
2.5
2
1.5
1
0.5
0
Mg
Mg/steel bolt
K+JS500
Source: MacDermid plc.
K+JS500/steel bolt
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%
75%
80%
60%
53%
40%
20%
0%
Chrome-free
Chromate
Keronite
Good thermal barrier
218
200
172
159
142
150
151
130
134
100
84
50
20
Keronite
α-Al2O3
2019
7075
2024
Al17Si4Cu
Al12Si
Al5Si
0
6061
1.6
99.5% Al
Thermal conductivity (W/m/K)
250
Keronite amorphous/multi-crystalline structure inhibits phonon transport
Stable up to 800ºC
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
N
F
µ
F = µN
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
Hard Anodic coating
Steel 5140 (50HRC)
0.14
0.55
1.47
Conclusion:
Keronite coating had wear resistance about 4 times higher than hard anodising and over ten
times higher than 5140 steel
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)
Throwing power
Coating on inner thread of M4 bolt hole
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.
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
Magnesium Applications
Magnesium applications
Corrosion protection
Keronite on magnesium body
and engine parts
BMW,VW approvals
Approved for US military use
on magnesium gearbox
casings
Keronite + ‘Rockhard’ epoxy
topcoat system
Production 2006
Allison
Transmission
Allison Transmission
Division of General Motors
Magnesium pistons
Keronite prevents skirt wear and
pin-hole wear
Under investigation in Japan,
Europe and USA
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
Nanomag piston-cylinder tribology results
Friction
Coefficient
mg
0,5
0,4
Magnesium
0,3
0,2
0,1
Time (s)
0
Am
piston wear
Cylinder
Am
cylinder
Piston
wear
7
6
5
4
3
2
1
0
Aluminium
0
500
1000
1500
2000
Al
Magnesium
Mg
Magnesium
Magnesium
Mg+K1
Mg+K2
Experimental Standard coating
coating
Piston material
Aluminium applications
Piston crowns
Thermal Barrier Test KERONITE on Al (400 C)
450
400
350
300
Temperature C
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
250
Heater Plate
200
Uncoated
KERONITE 40
mkm
150
100
50
0
0
2
4
6
8
10 12 14 16 18 20 22 24 26 28 30 32 34 36 38
Time (minutes)
Gasoline piston top ring groove
Issue
Wear of top ring groove during
engine life
4.4±1.5µm
3.5±1µm
Keronite surface
Approx. 500-1000HV (c.f Hard
anodising 300-350HV), 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
Top groove wear results
Max
Max
wear on wear on
top
ring
groove
1.8l I4 16V NA gasoline
engine
100 hour dyno test
cycling between max
power and max torque
Aluminium (ADC12)
piston
Nitrided steel ring
Total
wear
15µm
Hard
anodising
10µm
0.5µm
c10µm
5µm
Keronite
0.5µm
2µm
c2.5µm
Densitometry and porosimetry
10
5
Intra-flake porosity
0
0.20
0.15
0.10
FEGSEM Surface
-5
104
0.5 μm
-10
-15
-20
-25
-30
-35
105
Porosity (%)
0.25
Inter-flake porosity
Cummulative pore
pore volume
(ml/g)
Cumulative
volume
(ml/g)
15
Porosity (% from cut-off)
20
1000
100
10
1
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 m2 g-1 (BET)
Porosity ~ 20%
(Hg porosimetry, BET, skeletal density)
Pore diameter (nm)
Pore diameter (nm)
Source: Cambridge University
Nano-scale porosity is believed to be responsible for good oil retention
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
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
Piston
Diesel
pump
Mg FEM
Mg Housings
Transmission
Al strut
Al brake piston
case
Mg Wheel
FEAD pulleys
Mg door inner
Clutch ring Transmission
plate