Keith Legg 847-680-9420
Summary of coating integrity and planned testing
HCAT Program ReviewAugust 2001
Toronto
Keith Legg 847-680-9420
Big bar tests at NAWC, PAX River
#6, R= -1, WC-Co 0.012”
Failed at 180 ksi
#2, R= -0.33, WC-Co 0.012”
Test 1 180 ksi 20 cycle
Failed at 200 ksi
R= -1, WC-Co 0.003” Passed 220 ksi
#6
#2
Very sensitive to thickness.Insensitive to R
Very sensitive to thickness.Insensitive to R
Big bars not much different to small
Big bars not much different to small
Keith Legg 847-680-9420
Hill AFB re-optimization
WC-Co looks good to 240 ksi, R=-0.5
Note failures at higher substrate T, lower dep rate
Ctg Matl ThicknessPyrom T Dep rate R-ratio No Spall ksi Spall ksiWC-Co 0.005 220-230 -1.0 220WC-Co 0.005 220-230 -1.0 190WC-Co 0.015 220-230 -0.33 170 190WC-Co 0.005 165-175 -0.5 240WC-CoCr 0.010 165-175 0.5 0.1 220WC-Co 0.005 165-175 0.5 -1.0 190WC-Co 0.015 165-175 0.5 -0.5 190WC-Co 0.005 165-175 0.5 -0.33 190WC-CoCr 0.005 165-175 0.5 0.1 190WC-CoCr 0.005 165-175 0.5 -1.0 180WC-Co 0.005 165-175 0.5 0.1 180WC-Co 0.015 165-175 0.5 0.1 180WC-CoCr 0.005 165-175 0.5 -1.0 180WC-Co 0.015 165-175 0.5 -0.5 240WC-Co 0.005 ??? 0.2 -0.5 240WC-Co 0.015 ??? 0.25 -0.5 180
Spalling Data
0
50
100
150
200
250
300
-1.1 -1.0 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2
R-ratio
Ma
x s
tre
ss
, k
si
No Spall ksi
Spall ksi
WC-CoCr
WC-Co, 3 ptsWC-Co fail
We can make 0.005”, 0.015” WC-Co coatings that do not spall at 240 ksi, R=-0.5
Keith Legg 847-680-9420
Latest data from 40 specimens coated at Southwest Aero, 0.003”, 100 cycles at each load to 240 ksi
Smax @
R=-0.5
M5-7, WC-CoCr full M5-17, WC-CoCr patch
M5-28, WC-Co patch
M5-37, WC-Co full
190 Subsurface* Subsurface None None
200 Crack @ 51 cycles Subsurface None Subsurface & bulging**
210 Crack, no spalling Crack @ 60 cycles Crack @ 85 cycles, some subsurface
Same
220 Crack, no spalling Crack, no spalling Crack, no spalling Same
230 Crack, no spalling Crack, no spalling Crack, some bulging**
Same
240 Nf=3046 cycles, spalling @ fracture
Nf=3004 cycles, spalling @ fracture
Nf=3368 cycles, spalling
Crack @ 72 cycles, Nf=3716 cycles
WC-CoCr survived to 240 ksi and exceed NfDoes this mean WC-CoCr is not a lot more brittle than WC-Co?
WC-CoCr survived to 240 ksi and exceed NfDoes this mean WC-CoCr is not a lot more brittle than WC-Co?
Keith Legg 847-680-9420
Ogden ALC A-10 LG bend tests, R=-0.33
0.010” WC-Co deposited at OO-ALC using new parameters 500 cycles at loads to 190 ksi ultrasonic tests showed no delamination 50 cycles at loads >190 ksi no spalling at 240 ksi (yield) coating spalled at 256 ksi (>yield)
0.015” WC-Co spalled at low load - cause unknown
We can reach 240 ksi with thick coatingIs spalling very sensitive to thickness?
We can reach 240 ksi with thick coatingIs spalling very sensitive to thickness?
Keith Legg 847-680-9420
Conclusions to date
WC-Co and WC-CoCr can both exceed commercial requirements for OEM coatings (0.003”)
WC-Co can exceed Air Force (land-based aircraft) requirements for rebuild coatings
Spalling appears most sensitive to deposition conditions (how it is optimized) coating thickness
Spalling appears not very sensitive to sample diameter (details of coating morphology) R ratio (once you get interface cracking it does not
need a big push to delaminate)WC-Co looking likely to work for all but high-bend parts
Keith Legg 847-680-9420
Work to be done
Additional testing Additional samples and big bar tests at NAWC New samples and big bar tests at Metcut and AFRL Bend tests to examine D/T ratios at Hill Additional A-10 bend tests at Hill Bending fatigue of large cylinders at Goodrich
Process mapping Coatings can exceed requirements - let’s make sure we
know how to ensure they always do! Consideration of rebuild options
Ensure coating integrity through deposition control Duplex coatings (alloy build-up, carbide cap)
e.g. Long Beach Joe Kolek reported Tribaloy does not crack - is it a good rebuild, or is NiAl better (cc sulfamate Ni)?