corrosion testing acknowledgements to: paul natishan, rick foster, capt marty mahon center for...
Post on 27-Dec-2015
217 Views
Preview:
TRANSCRIPT
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 SteelAtmospheric Exposure For 3 Years
Thickness 0.004”, Coatings Not Ground
PROTECTION RATINGS FOR 4 MIL COATINGS OVER 4340 STEEL (PLATES)
0 2 4 6 8 10 12
WC/Co *
Triballoy 400 **
Hard Chrome, with nickelsublayer
Protection Ratings (10 = Best)
Edge
Face
** "T-400" (Stellite): 60% Co, 28% Mo, 9% Cr, 3% Si* Diamalloy 2005 (Sulzer-Metco): 83%WC, 17% Co
Additional Corrosion TestingTo 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, EHCOn 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 Testing4340 rodsCoating Thickness Ground Spray Co. # of samples
WC/Co 0.003” Y Hitemco 2
WC/Co 0.003” Y Southwest 2
WC/Co 0.003” N H 2
WC/Co 0.003” N S 2
WC/Co 0.010” Y H 2
WC/Co 0.010” Y S 2
WC/CoCr 0.003” Y H 2
WC/CoCr 0.003” Y S 2
WC/CoCr 0.003” N H 2
WC/CoCr 0.003” N S 2
WC/CoCr 0.010” Y H 2
WC/CoCr 0.010” Y S 2
EHC 0.003” Y S 2
EHC 0.010” Y S 2
Total 28
Repeat this exact matrix for the 4340 plates and the 300M rods.
August 2000 August 2001
breached coating
WC/Co coatings (ground) on 300M steel.
WC/Co coatings (ground) on 4340 steel.
August 2000 August 2001
breached coating
Comparison of hard chrome samples.
August 2000 August 2001
breached coating
Type 300M Metal Coating Appearance Ratings
0 2 4 6 8 10 12
WC/Co 3 Gr Hitem
WC/Co 3 Gr SWAero
WC/Co 3 UG Hitem
WC/Co 3 UG SWAero
WC/Co 10 Gr Hitem
WC/Co 10 Gr SWAero
WC/Co/Cr 3 Gr Hitem
WC/Co/Cr 3 Gr SwAero
WC/Co/Cr 3 UG Hitem
WC/Co/Cr 3 UG SWAero
WC/Co/Cr 10 Gr Hitem
WC/Co/Cr 10 Gr SWAero
EHC 3 Gr SWAero
EHC 10 Gr SWAero
Co
atin
g T
ype
Appearance Rating
Series2
Series1
Type 4340 Metal Coating Appearance Ratings
0 2 4 6 8 10 12
WC/Co 3 Gr Hitem
WC/Co 3 Gr SWAero
WC/Co 3 UG Hitem
WC/Co 3 UG SWAero
WC/Co 10 Gr Hitem
WC/Co 10 Gr SWAero
WC/Co/Cr 3 Gr Hitem
WC/Co/Cr 3 Gr SwAero
WC/Co/Cr 3 UG Hitem
WC/Co/Cr 3 UG SWAero
WC/Co/Cr 10 Gr Hitem
EHC 3 Gr SWAero
EHC 10 Gr SWAero
Co
atin
g T
ype
Appearance Rating
Series2
Series1
breached coating
WC/Co coatings (3 mil) on 4340 steel.
unground ground
general
corrosion
Comparison of HVOF and EHC coatings on 4340 steel.
general
corrosion
WC/Coground10 mil
WC/Co-Crground10 mil
EHCground10 mil
Comparison of HVOF and EHC coatings on 300M steel.
general
corrosion
WC/Coground10 mil
EHCground10 mil
WC/Co-Crground10 mil
breached coating
WC/Co coatings (3 mil) on 300M steel.
unground ground
general
corrosion general
corrosion
WC/Co coatings on 4340 steel.
ground10 mil
ground3 mil
breached coating
general
corrosion
WC/Co coatings on 300M steel.
ground10 mil
ground3 mil
breached coating
general
corrosion
general
corrosion
Comparison of HVOF and EHC coatings on 4340 steel.
general
corrosion
EHC10 mil
WC/Coground10 mil
Comparison of HVOF and EHC coatings on 300M steel.
general
corrosion
EHC10 mil
WC/Coground10 mil
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.
top related