Hydrogen Embrittlement Testing

1
Hydrogen Embrittlement Testing

• HCAT Program Review
• Cocoa Beach, Fl
• December 2000

2
Sequence 1 - Make sure that HVOFdoes not cause
embrittlement
Coat, no grind

• ASTM F-519, Type 1a.2
• 75 NTS
• All experience shows HVOF does not cause
  embrittlement
• Just makes sure

3
Sequence 2 - can H from other plating or
stripping escape through HVOF?
1. Bright Cd plate
2. Strip center - no bake
H2 fill
3. Coat within 4 hrs, no grind
Does H2 escape?

• 75 NTS
• Using bright Cd so as to avoid excessive diameter
  and inability to hold in grips
• No way for H to escape at center except through
  HVOF

4
Sequence 3 - How does environmental embrittlement
compare with Cr?
Coat
Expose small area in notch
expose

• 45 NTS
• Solutions - H2O and 5 NaCl
• Exposed notch should corrode and release H

5
Exposure of bare surface for Sequence 3

• Exposure of notch - 90? sector
• CNC machine using rounded edge blade (RBK,
  Seattle)

Blade
Sample
6
Hydrogen embrittlement

• Samples produced by Southwest Aeroservice (Jim
  Nuse, Dave Sommerville)
• Sequences 1 and 2 work by Metcut (Phil Bretz)
• Sequence 3 by Boeing (Dennis Dull)

7
Base material

• Expected NTS 260 ksi
• Tested at 362,416 to 382,521, average 373,600
  ksi
• Sequence 1 and 2 testing at 280.2 ksi
• Rockwell hardness

8
Coating deposition

• Chrome penetrates into notch
• thinner at notch bottom
• HVOF deposits best by angling gun and blowing
  excess powder away with strong jet
• thicker at bottom

Chrome
HVOF 31?
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Embrittlement - summary

• Table shows hours to failure (passgt200)
• Sequence 1
• Col 3 currently under test
• originals not baked
• Sequence 2
• Uncoated samples currently under test - no
  baseline yet
• originals not H-loaded
• Sequence 3 testing begun - uncoated baseline in
  test
• Blue samples at Boeing for metallography

10
Embrittlement - Sequence 1, not baked

• Sequence 1
• Unbaked Seq 1 show HVOF does not cause
  embrittlement
• Baked baseline (0.003 and 0.010 Cr only)
  currently under test
• Two Cr samples at Boeing for metallography to
  check failure mode

11
Embrittlement - Sequence 2, not baked

• No immediate failures
• Need to acquire uncoated baseline

• Baking removes most H2
• Not completely removed in WC-Co
• One immediate failure WC-CoCr 0.010
• Being analyzed at Boeing

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Embrittlement - Conclusions

• Sequence 1
• HVOF does not cause embrittlement
• Baked chrome baseline being acquired
• Sequence 3
• In progress

• Sequence 2
• Failure not immediate without bake
• Need baseline comparison
• Some H2 removal by flame?
• Reduced Kt?
• Bake removes H2 from most samples
• Except WC-Co 0.003 - why?
• Immediate fail WC-Co 0.010 being examined at
  Boeing
• Baseline uncoated (i.e. coated and stripped)
  being acquired