Keith Legg 847-680-9420

Overview of fatigue/spalling tests

HCAT Program ReviewLong Beach

April 2001

Keith Legg 847-680-9420

Findings so far

Wear - better than equal to Cr (mostly considerably better)

Fatigue - better than Cr Hydrogen embrittlement -

HVOF causes no embrittlement environmental embrittlement

under test Impact

Both Gravelometry and Whackometry show HVOF better than or equal to Cr

Rig tests F-18 pins “passed” Boeing test F-18 E/F fatigue and endurance

doing well at Messier-Dowty

Issues remaining Corrosion

C-HCAT data look good HCAT data had problems new samples being run

(Bruce Sartwell will report)

Spalling 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

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

C-HCAT findings 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

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 WC-Co, 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)

SurfaceSurface

InterfaceInterface BifurcationBifurcation

InitiationInitiation

Keith Legg 847-680-9420

User requirements

Commercial Typically 100 ksi, R=0.1,

thousands of cycles Maximum 170 ksi, R=0.1

Land-based military 180 ksi, R=-1, a thousand

or so cycles (Air Force) 240 ksi, R=-1, occasional

hard landings, (Air Force) Carrier-based military

Pins 235 ksi, R=-0.5, launch loads, 2,250 cycles, (OEMs)

Pistons 240 ksi, R=-1, occasional hard landings, (NAVAIR)

Yield stresses:4340M = 220 ksi 300M = 230 ksi A100 = 235 ksi

Yield stresses:4340M = 220 ksi 300M = 230 ksi A100 = 235 ksi

OEMs 0.003” typical

Airlines 0.010” or thicker for MRO

Repair Depots 0.010” or thicker for O&R

Keith Legg 847-680-9420

How many parts see maximum loads?

Thousands of landing gear cylinders, axles, pins currently chrome plated

Only a few pins see anything near yield stress, and do not see full stress reversal

loads are largely shear, not bending

Only a few inner cylinders see anything near yield stress, but do see full stress reversal

large bending loads Carrier-launched aircraft

have very small safety factor

Drag brace pins

Drag braceLaunch bar

Retract actuator pins

Keith Legg 847-680-9420

Major concerns

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 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 do not want a little left that requires we keep Cr tanks

running

Keith Legg 847-680-9420

0

50

100

150

200

250

300

-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1

R value

Lo

ad

(k

si)

Landing gear loads and R values

10 times

Hard carrier landinginner cylinders

Hard landinginner cylinders

1 time

Land-based military

1,000 times

2,250 times

Carrier launch drag brace pins

Normal 5,000 times

Commercial pins, cylinders, axles

Max 100 times

Keith Legg 847-680-9420

Tests run since August 2000

Additional tests and detailed materials evaluations - Orenda/NRC

Famous forty - smooth bar fatigue samples coated with WC-Co

tested at high load levels (John Sauer, Phil Bretz)

interrupted testing to track cracking and spalling

Prop hub specimens high residual stress

coatings (Engelhard), fatigue testing (Hamilton-Standard); high load testing (John Sauer)

A-10 Nose Landing Gear cylinders (Hill AFB)

using newly-optimized JP-5000 WC-Co (Jerry Schell)

bending stress spalling tests (Craig Edwards, Doug Wiser)

fatigue specimen spalling tests (Jerry Schell)

F-18 E/F Drag Brace spectrum loads, including

launch loads in-progress

HVOF WC-CoCr so far withstands spectrum loads on brace and pins

Keith Legg 847-680-9420

0

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300

-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1

R value

Lo

ad

(k

si)

Where we are now

Com

merc

ial

(last

cen

tury

)

WC-Co 0.003”, 0.010”July 2000

WC-CoCr 0.003”September 20000.010” WC-CoCrSeptember 2000

High-resid stress 0.015”WC-Co

Jan 2001

New JP-5000WC-Co

April 2001

OEM and rebuild

Carrier-basedDrag brace pinsOEM and rebuild

OEM and rebuild

Keith Legg 847-680-9420

Summary - what now looks doable

Commercial thin and thick WC-Co or

WC-CoCr Land-based military

thin and thick WC-Co, most parts, pins, etc.

except inner cylinders prone to hard landings (A-10)

Carrier-based military thin and thick WC-Co for

most components thin and thick WC-Co on

launch train components (pins, R=-0.5)

except inner cylinders

Issues remaining Do results on small

samples equate to real parts?

Inner cylinders (R=-1) not yet demonstrated

may require coating process refinement

Optimization 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?