HVOF in O&R
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Transcript of HVOF in O&R
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Keith Legg 847-680-9420 www.rowantechnology.com
HVOF in Repair and Overhaul -Higher reliability at lower cost?
Aviation Gas Turbine Engine O&R 2000
Keith LeggRowan Technology Group
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Technical information
Much of the technical information in this
presentation is derived from work of the HardChrome Alternatives Team (HCAT), withadditional information derived from work donefor the Joint Strike Fighter Integrated ProductTeam (JSF-IPT).
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Thermal spray use in GTEs
Tungsten Carbide
Cu-Ni-In
Al-Si-Polyester
Aluminum Bronze
Zirconium Oxide
Tungsten Carbide
Aluminum Oxide
Aluminum Oxide
T800T400
Aluminum Oxide
Aluminum
Fan Blade(Impact Wear)
Vanes(Sliding Wea r)
Se al Teeth(Abrasive Wear)
Se al Teeth(Cutting)
Casing(Abradable-Clearance)
Blade Dovetail(Fretting Wear)
Vanes(Sliding We ar)
Booster Cas e(Clea rance Control)
Flange(Impact Wear)
Combus tor Liner (Therma l Barrier)
Compressor Spool(Erosion)
Blad e Dovetail(Fretting Wear)
Coatings go from front to back
Wide te mpe ra ture rangeFrom s imple to comple x geome trie s
gCommercial Engine Cross Section
D. Comassar, GEAE
Thermalspray already
well usedin GTEs
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Rebuilding worn components
Most rebuild still specifies hard chrome plating orsulfamate NiHowever, we have learned a few things in the pasthalf century
Chrome is not very reliableHeavily dependent on who does it
You can get much better performance with other coatingsCost of ownership can be lowerFaster turnaround
Lower frequency of repairEPA and OSHA regs are affecting availability, risk, cost of Cr
Upcoming OSHA regs likely to increase cost and liability substantially
Ni is also on the EPA hit list, but a lower profile
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Drivers for chrome replacement
PerformanceHVOF often used wherechrome inadequate
Especially wear, fatigue,corrosion, seal life
Thicker rebuild possibleReclamation of moreparts
Greater choice ofmaterial and
performanceEnvironmental
Cr6+ reduction orelimination
Weakest driver
CostProcessing cost may behigher of lowerShorter processing timeBetter performance
lower cost of ownership
Risk Less processingEliminates H
embrittlementnot necessarily re-embrittlement
Competitive
Increasing user demand
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More stringent regulation
EPA stack emission fromchrome operations
Clean air act regs issued Jan 1995, full compliance Jan 1997, greatly reduced permissibleemission limits
0.03mg/dscm, small;0.015mg/dscm, large ornew
OSHA pel for Cr 6+Expected to issue forcomment by not toodistant future (but caughtin political fight)Current 100 gm/m 3
Expected 0.5-5 gm/m 3 would make EPA look like a pussy catlowest levels would
require respirators,greatly raising costs
Likely result: Fewer suppliers, higher costs
We should expect increasing cost and liability risk
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What is HVOF?
splat
Dry coating process -primary chrome plating
alternative, growing in useon engine and airframecomponentsDone in air in a spray booth,
usually robotic
Higher performance than Crand most other thermal
sprays, usually lower life-cycle cost
Available at job shops inmost areas
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Cost
There is no simple answer
Depends on what is important to you and how you do your cost-accountingIn-house or outsourceSize and materialsThe total production process and how HVOF fits into it
Cost may be 50% chromeFor large items of high strength steel coated in-house
Cost may be twice that of CrSmall items, outsourced, large batches
Net result - Need to evaluatecost for your specific situation
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Cost factors - coating deposition
Materials much highercostUsually requires diamondgrinding wheelsMay require
superfinishingSmall componentsinefficient30 min vs 12 hr processMasking usually simplerNo immersion, so may beno need to strip other
areasLarge, HSS componentsmost cost-effective
HVOF here
Leave paint here
Leave label here
Cost raising factors - Cost lowering factors
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Time Study
53
10.314.510.3
8686 24
0.520.320.3 12
1.511.510.510.5
62220
20
40
60
hvof manhours
cr plateman
hours
hvof process
hours
cr plateprocess
hours
m a s
k c l e a n
c o a
t / p
l a t e
u n m a s
k b a
k e g
r i n
d t o
t a l
BOEING 737 NLG IC PISTON
HVOF vs. Chrome Plating, Time in Hours
Sulzer Metco evaluation
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Cost factors - Performance
Wear life typically 3x chrome (or higher)Longer maintenance cycleNo maintenance needed on most cyclesLower parts inventory
Corrosion typically better than Cr, but
worse than CdLess severe pitting damageShould have lower stress corrosioncracking risk
Not as good as Cr + Ni strikeNo/low fatigue debit
No effect on costThicker rebuild (up to 0.060?)
More repairable components, less scrap
Flap and slat tracks
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Cost factors - Other
Accounting issuesFaster turnaround
Lower out-of-servicetime (hours vs days)Can shave days offproduction of large and
complex itemsInventory
Longer service life,lower inventory
can be major fleet costreduction
Capital cost (in-houseuse)
Capital cost $500k+ vs
fully depreciated chrometanks
Qualification cost
Environmental issuesNo contaminated solid
waste or rinse waterCooling water neededDust control andcollection
Worker safety Avoidance of Cr 6+ risk
No Cr 6+ even whenusing a chrome-containing coatingMay become important
with new OSHA pel forCr
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Cost studies
BFG - two evaluations (OEMcosts)
Assume do in-house - 40%cost reduction, taking in-factory time and cost ofmoney into accountContract out - similar to 2x higher cost for differentcomponents, based onbids from 3 contractorsincluding scrap, optimalbatch sizes
Rowan Technology Group(OEM costs)
HVOF 50% chrome for truck piston rings based largely on lower finishing cost
Mid-Atlantic Associates(O&R)
Transmission flange sealsurface - factor of 3 costreduction, based on longerlife, fewer replacements,thicker rebuild, reduceddowntime and inventory fora fleet
Coopers and Lybrand (O&R)HVOF for Cr replacement at
NADEP-Jacksonville.Payback in < 1 year
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Example - detailed cost comparison
for truck piston rings - new plant
D e p r e c i a t i o n
L a b o r
M a t e r i a l s
Pre-treating
Coating
Finishing/QA
$0.00$5.00
$10.00
$15.00
$20.00$25.00
$30.00
Labor 35%
Other 35%
Materials23%
Deprec.8%
ChromeChrome
Labor 31%
Materials58%
Other 6%
Deprec.5%
D e p r e c i a t i o n
L a b o r
M a t e r i a l s
Pre-treating
Coating
Finishing/QA
$0.00$5.00
$10.00$15.00$20.00$25.00$30.00$35.00$40.00$45.00
HVOFHVOF
lapping
Intensive grinding
Analysis of
CumminsPiston RingDivision
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Cost issues summary
Depends on what costs are important to youand how well you can capture your costs
Cost-of-ownership vs processing cost vs acquisitioncostCapital equipment costs
Various indirect costs:Risk - embrittlement, newer technology Environmental (EPA, OSHA) liabilitiesOverhaul - parts inventory costManufacturers - in-process time, cost of money
Airlines - out-of-service revenue losses - sealreplacement and major overhaul
Net result - Need to evaluatecost for your specific situation
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Growing applications of HVOF in O&R
Thermal spray in general, HVOF in particular,growing for O&R on airframe components
Supplanting chrome on landing gear, flap and slattracksUsers moving from plasma spray to HVOF for higher
quality higher performanceeasier grinding and finishing
From LPPS to HVOF for lower cost, e.g. HPT shroudsIncreasing usage on GTE shafts in place of chromeGrowing interest in replacing chrome with HVOFthroughout engines and hydraulics
want JSF to be a Cr, Cd, VOC-free aircraft
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GTE qualification of HVOF coatings for O&R
HCAT/PEWG program just beginningGE Aircraft Engines (Jerry Schell)Rolls RoycePratt and Whitney Oklahoma City ALC
Chrome replacement on a variety of components, substratematerials
Acquisition of detailed data on wear, fatigue, corrosion,producibility
Aim is qualification of O&R methods and materials
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Other systems for which HVOF
is being qualified for O&RLanding gear
BFG, Messier-Dowty, Heroux, Orenda, several depots
Hydraulic actuatorsParker Hannifin, Moog, etc.
Propeller hubsHamilton Sundstrand, Cherry Point NADHelicopter dynamic components
Jacksonville NAD
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Aerospace Applications
Landing gear
Slat and flap tracks
Chromed piston
Bushing -bronze, Al bronze
Wiper
Bearing
SealsBodyPistonseal
Wear, scoringWear, scoring
Sand and dirtSand and dirt
Chrome flakingChrome flaking
Side loadSide loadActuators
Engine shafts
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Successful replacements -
specs and qualified componentsSpecifications
BAC 5851 - new version
HS 4412 AMS 2447New AMS specs for powders,coating, finishing expected
2000 - 2001 AWS spec in progress
Qualifications - new itemsBoeing > 100 components
specd for thermal spray Boeing 767-400 has landinggear specd for chrome orHVOFBombardier Q400, GlobalExpress flap tracks HVOF,replacing electroless NiHamilton Sundstrand - F-22thrust vectoring actuator
Parker - no Cr on new hydraulic actuator designs
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Qualifications - repair
Boeing - HVOF approvedfor repair up to 0.010
Boeing evaluating thick build-up methodsNot yet complete butlooking very good
Wide usage on slat andflap track repairDelta - approved HVOF
for landing gear repairinner cylinders and axlesO&R turnaround andlower maintenance costs
United - moving towardin-house HVOF
TWI (UK) L-1011 Ti flaptrack repair (weld +HVOF WC-Co)CH 53 - blade damperF-18 polygon repair
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HCAT Landing gear fatigue - 4340
4340, R = -1, AIRLARGE (0.010"CTNG) VS. SMALL (0.003"CTNG) HOURGLASS
100.0
110.0
120.0
130.0
140.0
150.0
160.0
170.0
180.0
190.0
200.0
1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08
CYCLES TO FAILURE, N f
E N G I N E E R I N G S T R E S S M A X
, K S I
LgHG/EHC/PeenedLgHG/EHC/AverageLgHG/WCCo/PeenedLgHG/WCCo/AverageSmHG/EHC/PeenedSmHG/EHC/AverageSmHG/WCCo/PeenedSmHG/WCCo/Average
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Hydraulic testing - Green, Tweed
5
1 5
2 5
3 5
4 5
WC-Co, ACTTribaloy, ACT
Chrome, ACT
WC-Co-Cr, EnercapWC-Co, Enercap
Tribaloy, EnercapChrome, Enercap
0500
1000
1500
2000
2500
L e a
k a g e
r a m s
Cycles (millions)
50 million cyclesEnercap
PTFE seal ACT
Nitrile seal
Cumulative leakageNo HVOF rod wear
ACT sealsreplaced withEnercaps
Surface finish:EHC 4 RaT 400 9 RaWC-Co 4 RaWC-CoCr 6.5 Ra
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Flight tests
Flight tests by Lufthansa, Boeing, Delta All successful
Landing gear flight tests plannedP-3 Orion (Navy)Dash 8 (Bombardier)C-130 (Canadian Air Force)
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Finishing, stripping
FinishingMust grind with diamond
wheelSuperfinishing removesdebrisSmall level of porosity appears to hold fluid
Stripping of WCStandard electrochemicalRochelle salt - benignCannot be water jetstrippedT400 difficult to strip - nosimple methods
Component Value NotesAnhydrous sodium carbonate 20 - 30 oz/gal waterSodium potassium tartrate(Rochelle Salt)
8 - 12 oz/gal water
Temperature 104 - 150 F 130 -150 F optimal pH 11 - 12Voltage 4 - 6 V DC
Current density 4 - 8 A/sq in Parts are anodic (positive)
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Critical issues with use of HVOF
Process developmentProcess must produce
coating to match applicationMust optimize properly forthe most importantproperties
Dont use a wear coatingfor a fatigue application
Proper specsMust specify structure,porosity, substratetemperature, stressGrinding, finishing
Process controlDeposition conditions
Stable, well-controlledequipmentParticle velocity,temperatureCoating stress
Temperature of componentNDI for cracks in steel
FPI, Barkhausen work Eddy current can work, but
must be very sensitiveMPI does not work Better methods beingdeveloped
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Higher reliability? Almost certainly
Lower cost?Probably, but you have to check it out
Growth potential
Use of HVOF on landing gear, engines, andother aircraft components likely to increase as
Users and customers see more benefits from lowerlife-cycle cost and quicker O&R turnaroundHVOF is used to reclaim more heavily-worn parts
Increasing cost and concern over Cr and Cdespecially in Europecost and risk of Cr will rise much higher if OSHA pelstandards are set low
