Development of nano-co-p plating as a replacement for hard chrome for engine components

Transcription

1 Development of nano-co-p plating as a replacement for hard chrome for engine components Nihad Ben Salah, Materials Engineering S. Beskri and J. Sapieha - École Polytechnique (Montréal- Canada) SERDP/ESTCP Workshop - Surface finishing and repair issues Tempe, Az February 2008

2 Presentation outline Engine sections concerned nco-p plating requirements for the different applications Tests (to be) performed Main Results Future work

3 Engine sections concerned Hard Cr main application: R&O in cold sections mainly gear box components (gearshafts, seals, shafts, shaft coupling, torquemeter, ) nco-p potential applications other than Cr replacement: Corrosion protection (Cad and CrVI paints replacement) Bell UH-1N T400-CP-400 Raytheon Beech King Air 200 Series PT6A-41/42

4 nco-p requirements for the different applications Hard Cr replacement on steels: Thickness (3 to 20 mils) to restore dimensions Hardness (over 600Hv) Wear resistance Fluid compatibility Fatigue debit For Corrosion protection on steels (Cad and CrVI paints replacement): Thickness (0.3 mils) Corrosion resistance (sacrificial, protective?) Adhesion Impact on fatigue

5 Tests (to be) performed Adhesion test only Substrate Materials: 4340 steel (40-45HRC HCM3 steel (46-50HRC) 9310 steel (35-40HRC) IN718 Ti 6-4 Plating: Performed at Integran 3 thicknesses (0.3, 5-6, mils) HT and not heat treated Shot peened and not shot peened Tests: Adhesion (bend tests, micro-scratch) Hardness tests (nano and micro-indentation) Fluid compatibility (Fuel and oils compatibility) Wear (dry and tribo-corrosion in NaCl) Salt spray (ASTM B117) unscribed and scribed specimens Vs Cad plating and Alseal (Al diffusion) coating Fatigue (Rotating beam fatigue at high and low stresses)

6 Main results - Adhesion Adhesion (bend tests, micro-scratch) On 4340 steel (40-45HRC) Very good adhesion On HCM3 steel (46-50HRC) Very good adhesion On 9310 steel Very good adhesion On IN718 Nickel superalloy Very good adhesion On Ti-6Al-4V Bad adhesion

7 Main results Adhesion test Cr on 4340 steel. 10 mils nco-p on 4340 steel 5 mils nco-p on Ti-6Al-4V Cross section Cr on 4340 steel Cross section nco-p 5 mils on mil nco-p on HCM3 steel

8 Main results Adhesion test SEM observation of 10 mils nco-p-4340 steel (no HT) Cohesive rupture showing the very good plating adhesion to the substrate

9 Main results Hardness tests nco-p minimum hardness for all thicknesses not heat treated show a minimum hardness equal to the minimum required for Cr plating. After heat 500 F nco-p hardness increases up to 750HV. Young modulus increases when the thickness increases indicating probably a larger nano-grain. * Cr plating ncop HT (5-6mils) ncop no HT (5-6mils) nco-p no HT (10-15) * ncop HT (10-15mils) X nco-p 0.3 mils Hardness (HV200) Surface Distance from surface to interface Interface Nano-indentation (E: Young modulus) Plating E (GPa) Mean σ 2 0,3-0,5 mil as deposited mils as deposited mils HT mils as deposited mils HT Co microcrystalline Cr Cr Cr plating nco-p ncopht HT (5-6 (5-6mils) nco-p ncop no HT no (5-6 HT mils) (5-6mils) nco-p HT X (10-15 nco-p mils) no HT nco-p (10-15) no HT (10-15 ncop mils) HT (10-15mils) *

10 Main results Fluid compatibility Fuel tests per P&WC specifications (immersion 4h + bend test): No leaching No general corrosion Bend tests pass Oils test (3 oils were tested during RT and F) No leaching No weight change

11 Main results Salt spray ASTM B117 General corrosion occurs (discoloration after 24 hours) Instable Co oxides formation Co-P plating before salt spray (5 mils HT) Discoloration after 24 h of salt spray (5 mils HT) Chrome plating after 24 h of salt spray (5 mils)

12 Main results Salt spray ASTM B117 General corrosion occurs (discoloration after 24 hours) Instable Co oxides formation Random pitting into the plating, not through the plating No substrate corrosion occurs as long as the plating is thick enough: 0.3 mils not sufficient, 4 mils passes Plating Time to failure Heat treated and not heat treated specimens behave the same ncop is not sacrifical for steels Corrosion resistance better than Alseal Performance Ranking (ASTM B537) Co-P 5 mils No failure after 400h 10 Co-P 0.3 mil h 5-9 Cadmium No failure after 400h 10 Alseal h 9

13 Main results Salt spray ASTM B117 No substrate corrosion after 456 hours (Co-P 5 mils no HT and HT) Co-P 0.3 mil HT after 432 hours Not sacrificial (0.3 mil HT)

14 Main results Dry wear / pin on disk (ASTM G99) * bearing steel balls (60-62 HRC) were used Wear of nanocop is higher than chrome Increases when the load is higher and decreases when the speed is higher (not observed for Cr) tool steel counterpart ball wear is much severe with Cr than with nanoco-p Cr 2N 100RPM tours Friction coefficient is lower for nco-p than for Cr, and it is lower for HT nco-p plating Co-P 10 mils HT 2N 100RPM tours

15 Main results Tribo-corrosion in 3.6%NaCl (ball on flat ASTM G133) Al 2 O 3 ball was used Ball wear for Cr plating Ball wear for Co-P plating

16 Main results Rotating beam fatigue (on-going) Test conditions: Room temperature, R=-1, frequency: 2500rpm for high loads, 7000 rpm for low loads

17 Future work Specimen tests: Additional fatigue tests Microfractography Producibility: Plating selected parts (Integran) Finishing (P&WC) Inspection (P&WC) Component tests (P&WC)

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