can electroplated fe-c be an environmentally friendly ... · can electroplated fe-c be an...
TRANSCRIPT
Lars Pleth Nielsen, Tribology Center
Danish Technological Institute, Denmark
Can electroplated Fe-C be an environmentally friendly alternative to hard chromium and DLC coatings?
Can electroplated Fe-C be an environmentally
friendly alternative to hard chromium and DLC
coatings? Klaus Pagh Almtoft, Henrik Bækgaard,
Bjarke Hall Christensen, Jona Jacobsen,
Helle Iben Jensen, Christian Slot Jeppesen,
Lone Larsen, Jens Erik Lionett, Sascha Louring,
Claus Mathiasen, Dorthe Kjær Pedersen,
Preben Munch Pedersen, Kristian Rechendorff,
Henrik Horup Reitz, Jens Vestergaard
Prof. Per Møller
Dr.-Ing. Karen Pantleon
PhD student Jacob Obitsø Nielsen
A. H. Nichro Hardchrome
Timo J. Hakala, Helena Ronkainen,
Hanna Iitti, Jarkko Metsäjoki
Amaya Igartua
Francesco Pagano
Outline
■ Introduction – why is it interesting to find alternatives to Hard Chrome
■ Introduction to three different coatings:
• Electroplating: • New Fe-C coating
• PVD: • a-C:H • a-C:H:Si
■ Temperature stability of the developed coatings
■ Friction properties: • Scratch tests • Pin-on-disk (air/vacuum)
■ Summary and conclusion
Take home messages:
• DLC; air/vacuum
• Adding Si to DLC
• Hard Chrome
• Highest friction
• Highest wear
• FeC interesting
hardness
Hard Chromium – facts: ■ High hardness
■ Large thickness - more than 100 µm
■ Large components up to metric tons
■ Process temperature is low compared with other type of processes like PVD and thermochemical diffusion processes
■ The coating is very corrosion resistant
■ Microcracks -> lubricants
■ The coating can be used as food contact material and is not able to introduce allergy
■ Easy release properties due to low surface energy
Wear resistance
Hardness
Tribological properties
Corrosion resistance
High temperature resistance
Magnetic properties
Electrical conductivity
Solderability/weldability/joining
Food contact material
Catalytic properties
Easy release properties
Hydrophobic/hydrophilic properties
Color and appearance
Decorative appearance
Refractive index
Optical properties
Oxide formation/passivation
Hard Chromium has many properties
Wear resistance
Hardness
Tribological properties
Corrosion resistance
High temperature resistance
Magnetic properties
Electrical conductivity
Solderability/weldability/joining
Food contact material
Catalytic properties
Easy release properties
Hydrophobic/hydrophilic properties
Color and appearance
Decorative appearance
Refractive index
Optical properties
Oxide formation/passivation
Difficult to replace
with one unique
solution
The future of Hard Chromium
■ Hexavalent chromium need an authorization since it is listed on the REACH Annex XIV.
■ REACH is an abbreviation for Registration, Evaluation, Authorization and Restriction of Chemicals.
■ REACH entered into force in 1 June 2007, with a phased implementation over the next decade. The regulation also established the European Chemicals Agency, which manages the technical, scientific and administrative aspects of REACH.
The future of Hard Chromium
■ The sunset date for using chromium trioxide (Cr+VI) in Europe is September 21, 2017. After this date it is no longer allowed to use hexavalent chromium for any production in the surface treatment field without having an authorization.
■ March 21, 2016 is the latest date to apply for a such authorization. If an authorization is required it is specific to a substance and its application(s).
However, it is unique; Fink -
1925
Fink and Eldridge - 1924
Break through at Columbia
University and commercialize
the process
Printing rollers - 1928
Chromium
Copper
Steel
Possible alternatives:
Electroplating: Fe-C
PVD-DLC’s: a-C:H a-C:H:Si
Lets compare these coatings…
Electroplating: Fe-C
Possible alternatives:
Fe-C coating ■ Electrolyte: FeSO4 + stabalizing agent
■ Anode: Inert; Ti-Pt
■ Temperature: 30 - 60 °C
■ Current Efficiency ≈ 80% ■ Main difficulties being:
! Oxidation by air ! Varying pH level
Anode: Fe -> Fe2+ + 2e-
Cathode: Fe2+ + 2e- -> Fe
FeC coating, 24 hours – no adjustments
■ Stability: Continues plating for 24 hour in a 25L container
■ No adjustment made….
■ Stable pH ± 0,05
■ Electrolyte fully reduced
Rate: ~23 µm/h
PVD-DLC’s: a-C:H a-C:H:Si
Possible alternatives:
Introduction to PVD ■ Industrial unit (CC 800/9-Custom)
■ Reactive DC magnetron sputtering ■ DC/MF substrate bias
■ Deposition parameters: ■ a-C:H (C, Cr) ■ a-C:H:Si (C, Cr, Si) ■ Adhesion layer of CrN
■ Ar/N2/C2H2
■ Deposition temperature ~200°C
■ Thickness ~ 3 µm inc. adhesion layer
Substrates Targets/ cathodes
Literature; a-C:H
■ DLC doped with hydrogen; a-C:H
■ Often best under dry atmosphere or under vacuum
■ Low friction is caused by electrostatic repulsion of mating surfaces
■ Often 30 at. % hydrogen or higher -> superlubricity under vacuum - COF < 0.01
■ Limited temperature stability
• ~ 200 oC -> graphitization • Depending on composition, structure and doping
Literature; a-C:H:Si
■ Improved performance by adding Si to a-C:H
■ Tribological performance is less dependent on the environment -> COF below 0.05 at atmospheric pressure in a wide range of temperatures and humilities
■ The improved performance under humid conditions is ascribed to the
catalytic activity of Si dopants for surface hydroxylation -> formation of a lubricating water film
■ Increasing Si content: -> increase the total number of sp3 Si-C bonds -> increase hardness - more diamond like
■ Improved temperature stability
Introduction to PVD; a-C:H and a-C:H:Si
a-C:H a-
C:H:Si
CrN
Gradient
DLC
Substrate
Characterization/Properties:
Electroplating: Fe-C
Results – GDOES
Average carbon content of 0.85
wt%
Results – XRD; as deposited
Ferrite with very
small amount of
Fe2O3
Results – SEM; Cross-section
As deposited
Results – XRD; as deposited
Annealed at 205 ℃ for 1 hour Annealed at 315 ℃ for 1 hour
Results – SEM; Cross-section
205 °C-1h 315 °C-1h
As deposited
Results – TEM diffraction pattern
Tag Phase hkl d-spacing [Å] 1 Unidentified 3.13
2 Unidentified 2.61
3 Ferrite 110 2.12
4 Ferrite 200 1.48
5 Unidentified 1.21
Tag Phase hkl d-spacing [Å] 1 β-Fe2O3 013 4.05
2 Unidentified 3.02
3 Unidentified 2.60
4 β-Fe2O3 018 2.43
5 Ferrite 110 2.06
6 β-Fe2O3 11-11 1.65
7 Unidentified 1.52
As deposited
Results – TEM diffraction pattern
315°C-1h
Results – TEM diffraction pattern
Tag Phase hkl d-spacing [Å] 1 Unidentified 3.13
2 Unidentified 2.61
3 Ferrite 110 2.12
4 Ferrite 200 1.48
5 Unidentified 1.21
Tag Phase hkl d-spacing [Å] 1 β-Fe2O3 013 4.05
2 Unidentified 3.02
3 Unidentified 2.60
4 β-Fe2O3 018 2.43
5 Ferrite 110 2.06
6 β-Fe2O3 11-11 1.65
7 Unidentified 1.52
Tag Phase hkl d-spacing [Å]
1 β-Fe2O3 104 3.67
2 Unidentified 3.11
3 Unidentified 2.67
4 β-Fe2O3 11-5 2.36
5 Cohenite 201 2.22
6 Ferrite 110 2.11
7 Fe3O4 422 1.71
8 β-Fe2O3 21-6 1.64
9 Cohenite 301 1.60
10 Unidentified 1.55
11 Ferrite 200 1.49
12 Cohenite 123 1.31
13 Unidentified 1.22
As deposited 315°C-1h
Ferrite + undefined -> Ferrite, β-Fe2O3, Cohenite (Fe3C) +
undefined phases
Results – TEM diffraction pattern
Results – Hardness, FeC Future-tech microhardness tester FM-700.
Hardness maintained up 300 oC
■ High deposition rate ~23 µm/h
■ High hardness - 750 HV
■ Stable up to 300 oC
■ As deposited Ferrite + undefined phase
■ Heating to 300 oC -> Ferrite, β-Fe2O3, Cohenite (Fe3C) + undefined phases
Conclusion on, FeC
Sample As deposited 300 oC a-C:H:Si 2200 HV 2100 HV a-C:H 1600 HV Delaminated FeC 7.4 7.4
Results – Hardness, DLC’er ■ Annealing; 300° C for 2 hours in air.
500 1000 1500 2000 25000
1000
2000
3000
4000
5000
6000
7000
8000
Intens
ity(co
unts)
R amans hift(cm -1)
500 1000 1500 2000 25000
200
400
600
800
1000
1200
Intens
ity(co
unts)
R amans hift(cm -1)
� Graphitisation + change in mechanical properties " not temperature stable
D: sp2
G: sp3
Sample As deposited 300 oC a-C:H:Si 2200 HV 2100 HV a-C:H 1600 HV Delaminated FeC 7.4 7.4
G-peak
position (cm-1)
FWHM(G)
(cm-1)
I(D)/IG)
As made 1551±0.4 175±0.6 1.14±0.01
annealed 1561±0.3 157±0.4 1.41±0.01
Results – Hardness, DLC’er
• Decrease of FWHM -> ordering
• Increase in I(D)/I(G) increase in sp2 cluster size
■ Annealing; 300° C for 2 hours in air.
� Graphitisation + change in mechanical properties " not temperature stable
a-C:H hardness maintained up < 200 oC
a-C:H:Si hardness maintained up
~300 oC
■ Higher hardness than FeC ■ a-C:H; 1600 HV ■ a-C:H:Si; 2200 HV
■ Temperature stability;
■ a-C:H; ~200 oC ■ a-C:H:Si; ~300 oC
Conclusion on a-C:H and a-C:Si
Mechanical and Friction properties:
Scratch test parameters.
• Scratch tip: Rockwell C, R 200 µm
• Progressive load: 0.10 – 30 N
• Scratch length: 10 mm
• Scratch speed: 10 mm/min
• Scratch spacing: > 1 mm
• Loading rate: 29.90 N/min
• Prescan, postscan: 0.10 N
• Environment: 22±1 °C, 50±5 % RH
• # of scratches per specimen: 3 Substrate: DIN X155CrVMo12-1
Scratch test
Lc1 = 45° crack
Lc2 = edge delamination
Lc5 = crack formed on the bottom of the
scratch grove
Scratch test, Hard Chrome (100 µm)
Scratch test, FeC (thick) Lc1 very difficult to see
Lc2 = edge delamination
Lc5 = crack formed on the
bottom of the scratch grove,
which continues until the end of
the scratch
Fe-C thick:
Fe-C thin:
Lc1 Lc2
1 8.4 -
2 8.6 -
3 6.0 -
Average 7.7 -
STDEV 1.4 -
Lc1 Lc2
1 5.4 18.2
2 4.8 19.3
3 6 16.9
Average 5.4 18.1
STDEV 0.6 1.2
Scratch test, FeC (thick and thin)
Scratch test, DLC-TR (a-C:H)
Scratch test; Si-DLC (a-C:H:Si)
0.1 N 30 N
Scratch test
Results – Pin-on-disk experiments
■ Pin-on-Disc tribometer designed and manufactured at VTT
■ Test parameters: • AISI420 for all coatings • +Al2O3 for FeC and Si-DLC • Normal load 5 N • Sliding velocity 0.637 m/s • Duration 4 hours • Sliding track diameter
• 34 mm (85742 cycles) • 29 mm (100525 cycles)
FeC delaminated under the tests
conditions due to adhesion to the
ball (AISI420 / Al2O3)
Results – Wear
■ After tribological experiments the wear tracks were measured by 2D-profilometry
■ Wear track of the coated surface was
measured
■ Optical microscopy was used to measure the diameter of the worn surface on stainless steel balls after experiments
Results – Wear
■ COF was determined as the average value between 120-180 minutes of sliding
Results – Coefficient of friction (COF)
Sample COF Std a-C:H:Si (AISI420) 0.084 0.015 a-C:H:Si (Al2O3) 0.098 0.038 a-C:H 0.131 0.010 Hard Chrome 90 µm 0.890 0.017
■ TL: formation of tribolayer
Results – Wear
Sample Wear (mm3/Nm)
Std wear
a-C:H:Si (AISI420) 5.585E-07 5.40E-08 a-C:H:Si (Al2O3) 5.100E-07 5.40E-08 a-C:H 1.781E-07 5.62E-08 Hard Chrome 90 µm 1.124E-5 1.89E-06
Results – Wear rates
Results – Wear; air versus vacuum
Mass-spectrometer
Leak valve
Load-lock chamber
Main chamber
Sample transfer rod Tribometer
The UHV tribometer, allows to study behavior of materials, coatings and lubricants both in ultra high vacuum (P < 1x10-7 Pa) and in controlled environments.
2N
12N
Normal air:
2N
12N
Vacuum:
Air: a-C:H:Si lowest friction for
both loads
Results – Wear; air versus vacuum
Vacuum: a-C:H
lowest
Friction as a function of pressure a-C:H
a-C:H
a-C:H:Si
Friction of a-C:H:Si is much more pressure
dependent
Summary ■ FeC:
■ High hardness around 750 HV ■ Stable up to ~300 oC ■ High content of homogeneously distributed carbon ■ Cracking under pressure if it too thin
■ Scratch tests:
■ a-C:H coating deforms and does not crack ■ a-C:H:Si has a different failure mechanism as compared to a-C:H ■ Lc1 values decreases with increasing Hard Chrome thickness ■ Thick FeC delaminate
■ Pin-on-Disk
■ a-C:H:Si has the lowest friction in air ■ a-C:H reveals pressure dependent friction ■ a-C:H has the lowest wear rate ■ FeC coatings showed adhesive failures ■ Hard Chrome has high wear
Lars Pleth Nielsen, Director Tribology Center Danish Technological Institute Email: [email protected] Phone: +45 72201585
Wear: a-C:H < a-C:H:Si << Hard
Chrome
Temperature stability: a-C:H < a-C:H:Si < FeC <
Hard Chrome
Friction in air: a-C:H:Si < a-C:H << Hard
Chrome Friction in vacuum: a-C:H < a-C:H:Si << Hard
Chrome
Thick FeC + DLC might be an interesting alternative
Just send an email if you are interested in testing
our coatings