Keith Legg Overview of fatigue/spalling tests HCAT Program Review Long Beach April 2001

Keith Legg 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 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 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 Crack propagation in WC-Co (NRC/Orenda) Surface Interface Bifurcation Initiation

Keith Legg 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 OEMs  0.003” typical Airlines  0.010” or thicker for MRO Repair Depots  0.010” or thicker for O&R

Keith Legg 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 Retract actuator pins

Keith Legg 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 Landing gear loads and R values 10 times Hard carrier landing inner cylinders Hard landing inner 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 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 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 Where we are now Commercial (last century) WC-Co 0.003”, 0.010” July 2000 WC-CoCr 0.003” September ” WC-CoCr September 2000 High-resid stress 0.015”WC-Co Jan 2001 New JP-5000 WC-Co April 2001 OEM and rebuild Carrier-based Drag brace pins OEM and rebuild

Keith Legg 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?