Ogden Air Logistics Center Innovation & Excellence HVOF On-Going engineering Hill AFB –WC-17Co on 300M steel Summary of A-10 bend tests Compressive residual stresses Analysis Coating fade-out stresses Duplex coatings development Big Tube 4-PT Bend test for coating spallation HVOF implementation at Hill AFB

Ogden Air Logistics Center Innovation & Excellence

Ogden Air Logistics Center Innovation & Excellence Coating Integrity (Hill 15 mil)

Ogden Air Logistics Center Innovation & Excellence Coating Integrity (Hill 10 mil)

Ogden Air Logistics Center Innovation & Excellence

Ogden Air Logistics Center Innovation & Excellence Coating Integrity (Hill 15 mil)

Ogden Air Logistics Center Innovation & Excellence HVOF Residual Stresses in HVOF coating –Compressive residual stress in coating Delays spallation well into metal plasticity Keeps steel interface in compression –Two methods investigated as coated flat specimens X-ray diffraction MLRM (Modified Layer Removal Method) –Both methods show residual compressive stress in coating Magnitudes different MLRM provided as-coated residual stress depth profile Ground coatings used in landing gear service –What effect does controlled grinding have on residual compressive stress?

Ogden Air Logistics Center Innovation & Excellence HVOF

Ogden Air Logistics Center Innovation & Excellence HVOF

Ogden Air Logistics Center Innovation & Excellence HVOF Using techniques similar to MLRM –Investigated the effects of grinding (layer removal) on residual stress –Used cylindrical tube for analysis –FEA model used ANSYS –Residual stress simulated by applying temperature distributions Adjusted by trial and error to give stress distributions to match curves approximated to those measured by MLRM Technique used to “simulate coating removal” was accomplished by reducing stiffness (E) of outer layers –Thicknesses investigated in model 0.005” as coated ground to 0.003” 0.008” as coated ground to 0.005” 0.014” as coated ground to 0.010”

Ogden Air Logistics Center Innovation & Excellence HVOF

Ogden Air Logistics Center Innovation & Excellence HVOF

Ogden Air Logistics Center Innovation & Excellence HVOF

Ogden Air Logistics Center Innovation & Excellence HVOF Findings: –Proper grinding technique maintains compressive residual stress in coating To reach higher compressive stress zone in a thick coating –Grind off outer 0.003” of coating »Residual stress is non-uniform through first 0.003” Example –As-sprayed thickness = 0.010” –Finish ground thickness = 0.007” –Maintains compressive residual stress through coating thickness

Filleted Fade OutTapered Fade Out Maximum interface shear stress for applied stress of 180 ksi and 250 ksi

Ogden Air Logistics Center Innovation & Excellence HVOF Duplex coatings –Working with Praxair Surface Technologies (Dr. Daming Wang) to investigate duplex coatings for thick build-up repairs for landing gear components –Using 4-pt bend beams to study strain to fracture and spallation 4-Point Bend Test Schematic

Ogden Air Logistics Center Innovation & Excellence HVOF A01 max load A05 max load A06 max load A07 max load 0.5 inch

Ogden Air Logistics Center Innovation & Excellence HVOF Big tubes 4-pt bend test –48 tubes, 3” O.D. with various D/t ratios to be coated with HVOF 4340 steel ksi, shot-peened WC-17Co coating Different thickness coating, ground finish Obtain strain to fracture (first crack) Obtain strain at spallation

HVOF

Ogden Air Logistics Center Innovation & Excellence HVOF 2nd spray booth (JP-8000) installed at Hill AFB Nov 2002 Designing HVOF shielding (carbon steel) –Component specific –Precision designs Tooling drawings for each LG component Minimize overspray (difficult to remove with hand tools) Maintain fade-out at coating ends Rochelle salt stripping tank operational Diamond grinding wheels procured (hubs and wheels)

Ogden Air Logistics Center Innovation & Excellence HVOF Landing gear components approved for HVOF coating at Hill AFB –A-10 MLG Piston –A-10 NLG Piston –B-1 MLG Axle –C-130 MLG Piston –C-141 MLG Bogie Beam –C-141 Outer Cylinder –C-5 MLG Roll Pin –C-5 MLG Ball Screw –C-5 MLG Outer Pitch –F-15 Drive Keys –KC-135 MLG Axles