Transcript Overview of fatigue/spalling tests

Overview of fatigue/spalling tests
HCAT Program Review
Long Beach
April 2001
Keith Legg 847-680-9420
Findings so far
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Wear - better than equal to Cr
(mostly considerably better)
Fatigue - better than Cr
Hydrogen embrittlement - HVOF
causes no embrittlement
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Impact
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environmental embrittlement
under test
Both Gravelometry and
Whackometry show HVOF
better than or equal to Cr
Rig tests
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F-18 pins “passed” Boeing test
F-18 E/F fatigue and endurance
doing well at Messier-Dowty
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Issues remaining
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Corrosion
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C-HCAT data look good
HCAT data had problems
new samples being run
(Bruce Sartwell will report)
Spalling
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WC-Co looked good (not
perfect)
WC-CoCr spalled,
especially thick coatings
considerable progress
made in understanding and
improving performance
Keith Legg 847-680-9420
Overview of spalling/fatigue issues
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Summary of spalling issues
User requirements
Progress in meeting requirements - tests run
Results of Tuesday evening meeting
What can now be coated
Keith Legg 847-680-9420
Summary of spalling issues
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C-HCAT findings
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WC-CoCr, 0.003” spalled above 180 ksi
WC-CoCr, 0.010” spalled above 125 ksi
Evidence of less severe spalling on WC-Co runouts
Apparent mechanism
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cracks start at surface of coating, presumably growing in tensile
cycles
bifurcate or deflect at, or just above, interface
when cracks join up spall occurs on compressive cycle
Data suggests WC-CoCr is generally more brittle than WCCo, but Jerry Schell optimization suggests WC-CoCr can be
made similar to WC-Co
Keith Legg 847-680-9420
Crack propagation in WC-Co (NRC/Orenda)
Surface
Interface
Initiation
Bifurcation
Keith Legg 847-680-9420
User requirements
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Commercial
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Land-based military
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Typically 100 ksi, R=0.1,
thousands of cycles
Maximum 170 ksi, R=0.1
180 ksi, R=-1, a thousand or
so cycles (Air Force)
240 ksi, R=-1, occasional
hard landings, (Air Force)
Yield stresses:
4340M = 220 ksi
 0.003” typical
300M = 230 ksi
 Airlines
A100 = 235 ksi
 0.010” or thicker for MRO
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OEMs
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Repair Depots
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0.010” or thicker for O&R
Carrier-based military
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Pins 235 ksi, R=-0.5, launch
loads, 2,250 cycles, (OEMs)
Pistons 240 ksi, R=-1,
occasional hard landings,
(NAVAIR)
Keith Legg 847-680-9420
How many parts see maximum loads?
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Thousands of landing gear
cylinders, axles, pins
currently chrome plated
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loads are largely shear, not
bending
Only a few inner cylinders
see anything near yield
stress, but do see full stress
reversal
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Retract actuator pins
Only a few pins see anything
near yield stress, and do not
see full stress reversal
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Drag brace pins
Drag brace
Launch bar
large bending loads
Carrier-launched aircraft
have very small safety factor
Keith Legg 847-680-9420
Major concerns
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Depots are concerned that HVOF may be accepted by
OEMs and then be required in place of Cr, but that if
thick HVOF does not work, they will be in trouble
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must be able to use thick coatings for repair
repair must meet same performance criteria as thin OEM
coatings
If dispense with Cr, want to dispense with all of it
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do not want a little left that requires we keep Cr tanks running
Keith Legg 847-680-9420
Landing gear loads and R
Carrier launch
values
Commercial
pins, cylinders,
axles
drag brace
pins
Hard carrier landing
inner cylinders
Normal
2,250 times
5,000
250 Max 100 times times
300
10 times
Hard landing
inner cylinders
1 time
Load (ksi)
200
150
100
50
Land-based military
0
-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1
1,000 times
0
0.1
R value
Keith Legg 847-680-9420
Tests run since August 2000
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Additional tests and detailed
materials evaluations Orenda/NRC
Famous forty - smooth bar
fatigue samples coated with
WC-Co
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tested at high load levels
(John Sauer, Phil Bretz)
interrupted testing to track
cracking and spalling
Prop hub specimens
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high residual stress coatings
(Engelhard), fatigue testing
(Hamilton-Standard); high
load testing (John Sauer)
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A-10 Nose Landing Gear
cylinders (Hill AFB)
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using newly-optimized JP5000 WC-Co (Jerry Schell)
bending stress spalling tests
(Craig Edwards, Doug
Wiser)
fatigue specimen spalling
tests (Jerry Schell)
F-18 E/F Drag Brace
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spectrum loads, including
launch loads
in-progress
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HVOF WC-CoCr so far
withstands spectrum loads
on brace and pins
Keith Legg 847-680-9420
Carrier-based
Drag brace pins
OEM and rebuild
Where we are
now
OEM and rebuild
300
250
OEM and rebuild
New 150
High-resid stress
JP-5000
0.015”WC-Co
WC-Co
WC-Co
0.003”,
0.010”
WC-CoCr
0.003”
100
JanWC-CoCr
2001
April
2001
July
2000
September
2000
0.010”
September 2000 50
Commercial
(last century)
Load (ksi)
200
0
-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1
0
0.1
R value
Keith Legg 847-680-9420
Summary - what now looks doable
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Commercial
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Land-based military
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thin and thick WC-Co or WCCoCr
thin and thick WC-Co, most
parts, pins, etc.
except inner cylinders prone
to hard landings (A-10)
Carrier-based military
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thin and thick WC-Co for
most components
thin and thick WC-Co on
launch train components
(pins, R=-0.5)
except inner cylinders
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Issues remaining
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Do results on small samples
equate to real parts?
Inner cylinders (R=-1) not yet
demonstrated
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may require coating process
refinement
Optimization
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Are there issues with stress
corrosion cracking if we use
coatings with high
compressive residual
stress?
Can WC-CoCr be made as
good as WC-Co?
Keith Legg 847-680-9420