Transcript Corrosion Testing

Corrosion Testing
Acknowledgements to:
Paul Natishan, Rick Foster, CAPT Marty Mahon
Center for Corrosion Science & Engineering
Naval Research Laboratory
Washington, DC and Key West, FL
Atmospheric Corrosion Testing
Substrate Materials: 4340 steel
Substrate Preparation: For EHC, grit blast with 180-220 grit Al2O3
For HVOF, grit blast with 54 grit Al2O3
Coating Deposition:
EHC deposited following MIL-STD-1501
WC/17Co deposited using hybrid Diamondjet gun, hydrogen fuel,
Diamalloy 2005 powder
Tribaloy 400 deposited using Jet Kote II, hydrogen fuel, Stellite T-400
powder
Coating thicknesses of 0.004 inches
Tested as-deposited (no grinding)
Epoxy masking used on non-coated surfaces
HVOF and Hard Chrome Coatings on 4340 Steel
Atmospheric Exposure For 3 Years
Thickness 0.004”, Coatings Not Ground
PROTECTION RATINGS FOR 4 MIL COATINGS OVER 4340 STEEL (PLATES)
Edge
Hard Chrome, with nickel
sublayer
Face
Triballoy 400 **
WC/Co *
0
2
4
6
8
Protection Ratings (10 = Best)
** "T-400" (Stellite): 60% Co, 28% Mo, 9% Cr, 3% Si
* Diamalloy 2005 (Sulzer-Metco): 83%WC, 17% Co
10
12
Additional Corrosion Testing
To address significant discrepancy between previous B117 and atmospheric
testing on flat plates, and LG B117 testing on rods, additional B117
corrosion tests were conducted as follows:
Substrate Materials:
4340 rods, 1” diameter, 6” long
4340 plates, 3” x 4” x 3/16”
300M rods, 1” diameter, 6” long
Coatings:
WC/17Co, WC/10Co4Cr, EHC
On rods, coatings to be applied on curved surface, terminating 1” from one end
and 1/4” from other end (length of coating 4-3/4 inches)
On plates, only coat one face 3”-wide dimension coated edge-to-edge, on 4”-wide
dimension, coating to terminate 1/2-inch from edge (coated area is 3” x 3”)
Deposition parameters to match Landing Gear JTP, plus must follow Boeing
Spec. Sheet 160T1000 which requires that HVOF coatings not terminate with
a square edge, but shall taper from full to zero thickness over a minimum
length of 0.006 inches
EHC coatings ground to 16 Ra finish; some HVOF coatings ground to 8 Ra
Non-coated areas to be cadmium plated (including chromate conversion
coating) with slight overlap of EHC and HVOF coating
Additional Corrosion Testing
4340 rods
Coating
WC/Co
WC/Co
WC/Co
WC/Co
WC/Co
WC/Co
WC/CoCr
WC/CoCr
WC/CoCr
WC/CoCr
WC/CoCr
WC/CoCr
EHC
EHC
Thickness Ground
0.003”
0.003”
0.003”
0.003”
0.010”
0.010”
0.003”
0.003”
0.003”
0.003”
0.010”
0.010”
0.003”
0.010”
Spray Co. # of samples
Y
Y
N
N
Y
Y
Y
Y
N
N
Y
Y
Y
Y
Hitemco
Southwest
H
S
H
S
H
S
H
S
H
S
S
S
Total
Repeat this exact matrix for the 4340 plates and the 300M rods.
2
2
2
2
2
2
2
2
2
2
2
2
2
2
28
breached
coating
August 2000
August 2001
WC/Co coatings (ground) on 300M steel.
breached
coating
August 2000
August 2001
WC/Co coatings (ground) on 4340 steel.
breached
coating
August 2000
August 2001
Comparison of hard chrome samples.
Type 300M Metal Coating Appearance Ratings
EHC 10 Gr SWAero
EHC 3 Gr SWAero
WC/Co/Cr 10 Gr SWAero
WC/Co/Cr 10 Gr Hitem
WC/Co/Cr 3 UG SWAero
Coating Type
WC/Co/Cr 3 UG Hitem
WC/Co/Cr 3 Gr SwAero
Series2
Series1
WC/Co/Cr 3 Gr Hitem
WC/Co 10 Gr SWAero
WC/Co 10 Gr Hitem
WC/Co 3 UG SWAero
WC/Co 3 UG Hitem
WC/Co 3 Gr SWAero
WC/Co 3 Gr Hitem
0
2
4
6
Appearance Rating
8
10
12
Type 4340 Metal Coating Appearance Ratings
EHC 10 Gr SWAero
EHC 3 Gr SWAero
WC/Co/Cr 10 Gr Hitem
WC/Co/Cr 3 UG SWAero
Coating Type
WC/Co/Cr 3 UG Hitem
WC/Co/Cr 3 Gr SwAero
Series2
Series1
WC/Co/Cr 3 Gr Hitem
WC/Co 10 Gr SWAero
WC/Co 10 Gr Hitem
WC/Co 3 UG SWAero
WC/Co 3 UG Hitem
WC/Co 3 Gr SWAero
WC/Co 3 Gr Hitem
0
2
4
6
Appearance Rating
8
10
12
general
breached
coating
corrosion
unground
ground
WC/Co coatings (3 mil) on 4340 steel.
general
corrosion
WC/Co
ground
10 mil
EHC
ground
10 mil
WC/Co-Cr
ground
10 mil
Comparison of HVOF and EHC coatings on 4340 steel.
general
corrosion
WC/Co
ground
10 mil
EHC
ground
10 mil
WC/Co-Cr
ground
10 mil
Comparison of HVOF and EHC coatings on 300M steel.
general
general
corrosion
breached
coating
unground
corrosion
ground
WC/Co coatings (3 mil) on 300M steel.
general
breached
coating
corrosion
ground
3 mil
ground
10 mil
WC/Co coatings on 4340 steel.
general
corrosion
general
breached
coating
corrosion
ground
3 mil
ground
10 mil
WC/Co coatings on 300M steel.
general
corrosion
EHC
10 mil
WC/Co
ground
10 mil
Comparison of HVOF and EHC coatings on 4340 steel.
general
corrosion
EHC
10 mil
WC/Co
ground
10 mil
Comparison of HVOF and EHC coatings on 300M steel.
SUMMARY OF CORROSION TESTING
 10 mil thick coatings fared better than 3 mil coatings of any
composition in protecting the substrate.
 The company applying the coating does not have a measurable,
definitive effect on coating performance (given the small sample set).
 Salt fog cabinet used at Kennedy Space Center appeared to be slightly
more aggressive than one used at Naval Research Laboratory
 EHC coatings outperform all other coating compositions, regardless of
thickness in this year’s B117 test.
 At 10 mil thickness, the data set infers WC/CoCr coatings show
improved performance over WC/Co coatings, though one 10 mil
WC/Co-Cr coating was breached.