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HELICOPTER DYNAMIC COMPONENTS JTP FATIGUE TESTING

HCAT Review Meeting23-25 January

New Orleans, LA

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SUBSTRATES/HT CONDITION• 4340: HRc 32-37 (UTS 150-170 ksi)• PH13-8Mo: H1050 per AMS 5629 (UTS 175 ksi)• 9310: HRc 35-40 core with HRc 59-62 carburized case

– Specimens carburized to 0.030” case depth then finish ground to a final case depth of 0.024”

• 7075-T7351 (UTS 65-75 ksi)

• Steel specimens peened per AMS 2432, 100% coverage, 8-10A intensity, CW14 shot

• 7075 peened in 2 lots– Per AMS 2430, 12-16A intensity, ASR 230 shot (Metal Improvement)– Per AMS-S-13165-97, 0.00849A intensity, S230 shot (SW United)

(Bare specimens tested as-peened)

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COATINGS

• HVOF (Hitemco)– WC-Co– WC-Co-Cr – T400+WC-Co: 0.007-0.009”+0.003-0.004”– T400: Sprayed by not tested

• EHC (SOUTHWEST UNITED)– IAW MIL-STD-1501 & QQ-C-320– No underlayer or sealer

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SUBSTRATE/COATING MATRIX

COATING THICKNESS PH13-8Mo 9310 7075-T7351 4340

EHC .010-.011 10 10 10 5

WC-Co 010-.011 10 10 10 3

WC-Co-Cr 010-.011 10 10 10 3

T400+WC-Co 010-.011 10

EHC .003-.004 10 10 10 5

WC-Co .003-.004 10 10 10 3

WC-Co-Cr .003-.004 10 10 10 3

Bare/Peened 10 10 10

(T-400) BOTH 10 10 10 3

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COATING & FINISHING• Target coating finish

– HVOF: 8-10 Ra– EHC: 12-16 Ra– Final ground & polished coating thickness 0.0035-0.0040” &

0.0105-0.0110”

• First group of 0.003” EHC on 7075 had insufficient thickness for grind & polish. A 2nd set of specimens (20) was peened by SWU followed by EHC plating on 10 specimens. To be tested.

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0.5” Coating Patch

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FATIGUE TEST CONDITIONS

• Room temperature• Stress ratio: R = 0.1• Frequency: ≤ 60 Hz without encountering

heating above 125°F • 10 specimens/curve for 13-8, 9310, & 7075• 3-5 specimens/coating for 4340 @ 105 cycles

(130 ksi).

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2360-83163 Fatigue Data Room Temp, R = 0.1, PH 13/8 Mo

130

140

150

160

170

180

190

200

1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08

Cycles

Max

Str

ess

(ksi

)

bare/peened EHC (0.011 in) EHC (0.003 in) WC-CoCr (0.011 in)WC-CoCr (0.003 in) WC-Co (0.011 in) WC-Co (0.003 in) T-400

Large data points (6) indicate cracking observed

at <10,000 cycles

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2360-83163 Fatigue DataRoom Temp, R = 0.1, 9310 (steel)

155

160

165

170

175

180

185

190

195

200

205

210

215

220

1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08

Cycles

Max

Str

ess

(ksi

)

bare/peened EHC (0.011 in) EHC (0.003 in) WC-CoCr (0.011 in)WC-CoCr (0.003 in) WC-Co (0.011 in) WC-Co (0.003 in)

Large data points (3) indicate cracking observed

at <10,000 cycles

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2360-83163 Fatigue DataRoom Temp, R = 0.1, 7075-T7351

20

25

30

35

40

45

50

55

60

65

70

75

80

85

1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08Cycles

Max

Str

ess

(ksi

)

bare/peened (MRI) bare/peened (SW) EHC (0.011 in)EHC (0.003 in) WC-CoCr (0.011 in) WC-CoCr (0.003 in)WC-Co (0.011 in) WC-Co (0.003 in) T400+WC-Co (0.011 in)

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0.011" COATINGS ON 4340

125

130

135

140

145

150

155

1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08

Cycles

Max

Str

ess

(ksi

)

EHC WC-Co-Cr WC-Co

2 pts. each

Large data point indicates cracking observed at

<10,000 cycles

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0.003" COATINGS ON 4340

125

130

135

140

145

1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08

Cycles

Max

Str

ess

(ksi

)

EHC WC-Co WC-Co-CrLarge data point indicates

cracking observed at <10,000 cycles

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FATIGUE BEHAVIOR OBSERVATIONS

• Fatigue life rankings by substrate– HVOF >> EHC on 9310– HVOF > EHC on PH13-8Mo– HVOF ≥ EHC on 7075

• The difference between HVOF and EHC is greatest at lower stresses near the fatigue limit

• Fatigue life rankings by coating– WC-Co ≈ WC-Co-Cr on all 3 substrates– T400+WC-Co ≥ other HVOF coatings on 7075

• Fatigue life rankings on 4340 substrate– 0.003”: WC-Co-Cr > WC-Co ≈ EHC– 0.011”: WC-Co-Cr ≥ WC-Co >> EHC

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15

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Cracking detected at

2,300 cycles

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18

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POST-TEST COATING BEHAVIOR

COATING THICK PH13-8Mo 9310 7075-T7351 4340

EHC .010-.011Crack 0/10

“Spall” 10/10Crack 0/10

“Spall” 10/10Crack 0/10Spall 0/10

Crack 0/5“Spall” 1/5

WC-Co 010-.011Crack 3/10Spall 9/10

Crack 0/10Spall 10/10

Crack 1/10Spall 1/10

Crack 0/3Spall 0/3

WC-Co-Cr 010-.011Crack 10/10Spall 9/10

Crack 9/10Spall 6/10

Crack 1/10Spall 3/10

Crack 2/3Spall 0/3

T400+WC-Co 010-.011

Crack 0/10Spall 0/10

EHC .003-.004Crack 0/10Spall 0/10

Crack 1/10Spall 0/10

TBDCrack 0/5Spall 0/5

WC-Co .003-.004Crack 10/10Spall 10/10

Crack 8/10Spall 5/10

Crack 1/10Spall 1/10

Crack 3/3Spall 0/3

WC-Co-Cr .003-.004Crack 10/10Spall 10/10

Crack 8/10Spall 9/10

Crack 0/10Spall 0/10

Crack 1/3Spall 0/3

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COATING BEHAVIOR OBSERVATIONS• Post-test cracking overwhelmingly circumferential

(ring) type.• No indications of spalling during tests.• Limited detection of cracking during tests, despite

frequent post-test evidence of cracks.• Some indications of load-carrying capability of HVOF

coatings vs. non-load bearing EHC.– Nf for 0.011” HVOF > 0.003” HVOF– Nf for 0.011” EHC < 0.003” EHC– More frequent end-of-patch failure for 0.011” HVOF vs.

0.003” coating. Low occurrence for EHC

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SUMMARY REMARKS

• As in prior HCAT programs, the fatigue performance of HVOF coatings is equal to or exceeds that of EHC plating.

• The HVOF coatings exhibit moderate to severe spalling (coating debonding) at fracture, whereas plating loss for EHC generally is limited to the near-fracture region.

• The fatigue performance of the HVOF coatings apparently is not compromised by cracking (ring-type) relatively early in the test (<10K cycles).