anti-wear improvement of stamping die materials through
TRANSCRIPT
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GDIS2018
Anti-Wear Improvement of Stamping Die
Materials Through Duplex Chroming
Eric McCarty
Auto/Steel Partnership
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#GDIS | #SteelMatters 3
1. Introduction
2. Sample Matrix
3. Test Method
4. Test Results
5. Failure Mechanisms
6. Summary
7. Conclusions
Agenda
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#GDIS | #SteelMatters 4
Introduction
Chrome plating and nitriding have been used to improve the durability and
wear resistance of stamping dies. • Chrome plating….
− is a thin hard coating
− is good for low load wear resistance
− can lower the coefficient of friction
− is not good for high load wear resistance and subject to peeling, chipping,
deformation and wear, spalling, etc.
• Nitriding….
− produces a hard iron-nitride layer for improved wear resistance.
− not as good as chrome plating for low load wear resistance
− Better than chrome plating for high load wear resistance where the thicker
nitride layer can better absorb vertical and tangential (sliding) loads
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Introduction
Project Hypothesis: Adding a nitride layer between the chrome plating and the
substrate die material can improve sliding-impact wear
performance by combining the lower friction of the chrome
coating with improved load support of the nitride coating.
The combination of chrome plating over nitriding is called …
Duplex Chroming
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Sample Matrix
Test Set-up
• A = Duplex Chrome: Thick chrome layer over nitrided substrate with a white layer
• B = Duplex Chrome: Thin chrome layer over nitrided substrate without a white layer
• C = Thin chrome plate over a relatively soft substrate
• D = Thin chrome plate over hardened substrate
Sample Cr thickness
(um)
Substrate 0050A
initial hardness
(HRC)
Heat treatment Post-treatment Nitrided substrate hardness,
before coating (HRC)
Coating
hardness
(HRC)
A 45 20 Ion nitriding
(Sun Steel)
white layer = 0.0002 -0.0004
in.
67 70
B 12 20 Ion nitriding
(Teikuro)
No white layer
Diffusion Layer = 0.008-0.015
in.
45 - 47 70
C 9 20 NA NA NA 70
D 9 60 Flame
hardening
NA NA 70
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#GDIS | #SteelMatters 7
Sample Matrix
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Test Method
• Dies Steel Substrates: S0050A
• Testing Load Condition: 30 N – 160 N contact mode
• Test Cycles: 150, 300 and 500 cycles
• Counterface Materials: SAE 52100 steel balls
• Steel Ball Size: 10mm in Diameter
• Length of Wear Tracks: 3 - 6mm 30
160
Head Tail
Die wear during the stamping operation is due to
stretching motion of the steel sheet over the
surface of the die: - sliding with inclined contact
The Inclined Sliding Wear Test Method
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#GDIS | #SteelMatters 9
Head Tail
Test Method
Bonding layer (for PVD coating)
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Test Method
1 - Chipping
2 - Peeling
3 - Material transfer
Partially exposure of the bonding
layer and substrate
Bonding layer
(for PVD coating)
Illustration of failure
mechanisms
Chipping
Peeling
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#GDIS | #SteelMatters 11
Test Results
Sample A
Sample D
Sample B
Sample C
150 cycles 300 cycles 500 cycles 3000cycles
(200 N / 400 N)
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Sample A
Sample D
Sample B
Sample C
300 Cycles
All
Samples
Tail Middle Head
Test Results
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Tail
A = Duplex Chrome: Thick chrome layer over nitrided substrate with a white layer
Middle Head
Test Results
300
Cycles
Sample A
Wear Track
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#GDIS | #SteelMatters 14
Failure Mechanisms
450 tilted
Steel (cross section)
Surface
Chrome
(cross section)
Exposed
steel
Steel (cross section)
Chrome
(cross
section)
Surface
Surface
Head Middle 300
Cycles
Sample A
A = Duplex Chrome: Thick chrome layer over nitrided substrate with a white layer
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Failure Mechanisms
A = Duplex Chrome: Thick chrome layer over nitrided substrate with a white layer
300
Cycles
Sample A
Steel (cross section)
Chrome
(cross section)
Surface
Crack initiating from
the coating /
substrate interface
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#GDIS | #SteelMatters 16
B = Duplex Chrome: Thin chrome layer over nitrided substrate without a white layer
Failure Mechanisms
450 tilted
Tail Middle Head
Optical
(Surface)
SEM
(cross section)
Cross section
Surface
300
Cycles
Sample
B
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#GDIS | #SteelMatters 17
Failure Mechanisms
Cross section (steel)
Cross section (steel)
Surface
(Chrome)
Surface
(Chrome)
Chrome
Surface
(chipped chrome)
Surface
(chipped chrome)
Only cracking, chipping and material
transfer
300
Cycles
Sample B
B = Duplex Chrome: Thin chrome layer over nitrided substrate without a white layer
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#GDIS | #SteelMatters 18
Tail Middle Head
Failure Mechanisms
450 tilted
Cross section
Surface
300
Cycles
Sample C
C = Thin chrome plate over a relatively soft substrate
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#GDIS | #SteelMatters 19
Head
Region
Failure Mechanisms
Steel
Surface
Chrome
Steel
Surface
Chrome
Cracking,
chipping,
peeling,
Sink-in
(deformed)
300 Cycles
Sample C
C = Thin chrome plate over a relatively soft substrate
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#GDIS | #SteelMatters 20
Tail Middle Head
Failure Mechanisms
450 tilted
Cross section
Surface
300
Cycles
Sample D
D = Thin chrome plate over hardened substrate
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#GDIS | #SteelMatters 21
Fracture Mechanisms
Head-Middle Region
Chipping, Peeling,
Materials-transfer
300 Cycles
Sample D
D = Thin chrome plate over hardened substrate
21
Exposed steel (Surface)
Surface (Cr)
Steel (cross section)
Steel (cross section)
Cr (cross section)
Surface
(after the chipping
of chrome)
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#GDIS | #SteelMatters 22
Summary
• The failure modes of all chrome plated samples included fatigue
cracking, chipping, peeling, material transfer.
• Most cracks started from the surface of the chrome coating and
extended into the interface between coatings and steel substrates.
• Sample A (Duplex Chrome: Thick chrome layer over nitrided substrate
with a white layer)
− Appeared to also have cracks initiating from the interface between
the coating and substrate, which may be due to the brittle white
nitride layer.
− The chrome coating was worn out and the steel substrate was
largely exposed at the head and middle regions of wear track.
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#GDIS | #SteelMatters 23
Summary
• Sample B (Duplex Chrome: Thin chrome layer over nitrided substrate
without a white layer)
− Performed the best
− Seemed to have only a chipping problem at the middle region of the
coating’s wear track and the steel substrate was not exposed at any
of the test cycles.
• Sample C (Thin chrome plate over a relatively soft substrate)
− Showed large cracks and the coating peeled everywhere. The
chrome coating seemed to have a good adhesion to the substrate
but the relatively soft substrate was deformed (sunk in).
− Long-term durability of this surface treatment appears problematic.
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Summary
• Sample D (Thin chrome plate over hardened substrate)
− Showed a large transfer of material at the middle and head regions
of the wear track.
− The steel substrate was locally exposed where the coating was worn
off mainly by chipping and peeling.
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#GDIS | #SteelMatters 25
• Duplex chrome surface treatments without a nitriding white layer can
significantly increase the wear resistance and durability of stamping die
steels
• The ranking of all the S0050A samples:
at 150 test cycles: B ≥ A > C > D
at 300 test cycles: B > D > C > A
at 500 test cycles: B > D > C > A
at 3000 test cycles: B > D > C > A
Conclusions
A = Duplex Chrome: Thick chrome layer over nitrided substrate with a white layer
B = Duplex Chrome: Thin chrome layer over nitrided substrate without a white layer
C = Thin chrome plate over a relatively soft substrate
D = Thin chrome plate over hardened substrate
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For More Information
Eric McCarty
Auto/Steel Partnership
248.945.4778
D.J. Zhou
FCA US LLC
248.944.1197
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#GDIS | #SteelMatters 27
Stamping Tooling Optimization Timeline
2007-2008: CVD/PVD coatings on hardened tool steels - D2
− not so good due to lack of enough load support
2009-2011: Duplex PVD coatings plus nitriding on tool steels
− force hard coatings suppliers collaborating with heat treatment suppliers
2012-2014: Duplex PVD coatings (containing C or MoS2 for friction reduction) plus nitriding on steels
− good for DP 980 MPa AHSS as demonstrated in industrial stamping trial
2015-2016: Nitriding for cast iron and cast steels
− Evaluated plasma nitriding, gas nitriding, and fluidized-bed nitriding
2016-2017: Chrome for cast steels
− duplex chrome – Chrome on nitrided steels, vs. Chrome on hardened/unhardened steels
2016-2018: Duplex PVD coatings (with multilayers for increased fracture toughness) on tool steels
− 2 candidates are good for DP 1180 MPa AHSS shown in industrial stamping trial
Goal: To strategically develop coatings and heat treatment technologies and suppliers through
evaluation using Impact-Sliding Fatigue Wear Tester