Overview of planned additional work

1. Overview of planned additional work HCAT Program Review Long Beach April 2001

2. Too hard (>1300HV) is bad excessive alloying into Co? Overheating is bad alloy tempering particle overheating and carbide dissolution Substrate heating improves splat flow Full gage vs patch coatings little or no difference (if anything recent data show more tendency for patch delamination) Recently optimized coatings at Hill AFB doing very well Survive 240 ksi at R=-0.5 Almen = 10 compressive Strongest determinant of compressive stress is particle size Ideal phase structure not yet known Prop hub data show excellent results High compressive residual stress (Almen = -20) What seems to work best? General coating conditions

3. Demonstration of coating integrity to 240 ksi, R=-1 Test on realistic sample size Stress corrosion cracking If we need higher coating compressive stress, does that worsen SCC? WC-Co vs WC-CoCr In past WC-Co generally showed less spalling than WC-CoCr. Recent work by Jerry Schell shows little difference. Can we get equivalent optimized performance? Optimization and testing Tests of full-scale pins and cylinders Tests of high residual stress and newly optimized coatings Coating optimization for spalling resistance Note - HVOF coatings can and should be optimized for desired property Limited SCC and fatigue tests to ensure spall-optimized coating does not cause problems elsewhere Issues to be resolved

4. Compressively stressed coatings

5. 240 max tensile 180 max tensile 240 max compressive 300 max compressive Effect of residual compressive stress • Compressive residual stress decreases crack initiation and propagation • Reduces damaging tensile stress, increases compressive stress • might cause delamination if interface cracks build up

6. Substrate tensile Almen=-20 Almen=-10 Note - equal area Coating compressive Effect of compressive residual stress Note: Stresses and depths are rough 40 0 • Conclusion: • tensile<<compressive • substrate fatigue and SCC will be a little worse, but effects will be low for reasonably attainable compressive coating stresses Stress (ksi) Compressive coating + shot peen: Large compressive stress in coating Some reduction of compressive near-surface stress Some increase in tensile stress subsurface More compressive coating + shot peen: Larger compressive stress in coating More reduction of compressive near-surface stress Larger increase in tensile stress subsurface Shot peen: Large compressive stress near surface Much smaller tensile stress deeper Compressive coating: Large compressive stress in coating Much smaller tensile stress subsurface More compressive coating: Larger compressive stress in coating Larger increase in tensile stress subsurface -100 Based on Wigren, Volvo Aerospace - actual numbers very rough 0 Depth (inch) 0.010 0.100

7. BIG samples

8. 1/4” dia samples have non-optimal HVOF, but high current density gives better EHC Most parts are >1” OD LG inner cylinders usually>2.5” On small parts coating is larger percentage of total area coating may carry significant load especially thick coatings Normal incidence Grazing incidence Small samples vs large 1 - 6” dia Always near normal incidence 1/4”

9. NAVAIR (Eui Lee) Evaluate spalling for full-size samples Axial stress Stop-frame testing Evaluation of spalling and delamination thresholds Metcut (Phil Bretz) Same sample OD/ID, design somewhat different Stop-frame testing Evaluation of different coating parameters based on results of small-sample tests Evaluation of spalling thresholds Large sample testing Time scale - ASAP

10. A-10 cylinder testing - Hill AFB WC-Co Testing of actual cylinders with newly-optimized coating done at OO-ALC Flexure, rather than axial loads (simulates use) Primary concern is performance of thick repair coatings Simulated LG piston tests - BF Goodrich WC-CoCr 5” and 10” dia simulated LG pistons (not actual parts) Flexural fatigue tests (not specifically spalling tests) Testing of landing gear cylinders Time scale - in-progress Time scale - 2 or 3 months

11. Messier-Dowty F-18 E/F NLG Drag Brace fatigue/endurance test spectrum loading including launch loads F-18 E/F NLG full scale fatigue test BF Goodrich Bombardier Dash8-400 MLG full scale fatigue qualification test spectrum loading Rig testing Time scale - begin shortly Time scale - in-progress

12. Process validation for high load regime • Testing of high residual stress coatings • Small and large samples • Determination of optimum coating structure/phases • Evaluation of “good” and “bad” coatings • Definition of optimum coating properties and deposition methods • Process optimization for best coating performance at high load • Process window determination • Evaluation of fatigue (a few points to define curve) and stress corrosion cracking Time scale - begin shortly

13. Determine whether HVOF can reach performance requirements of worst case - launch and landing for carrier-based aircraft Based on full-scale testing and rig tests If HVOF coatings cannot be used for worst case define spalling limits, if less than fatigue life (designer need) define where HVOF WC can and cannot be used (depot need) Establish validity, or otherwise, of small-sample tests Optimal material and process definition for high-load components Must have adequate window and be doable by OEMs, vendors, depots Determine whether we will need different process or material definitions for high and low-load parts Not possible with EHC Final outcome expected