Keith Legg 847-680-9420
Hydrogen Embrittlement Testing
HCAT Program ReviewCocoa Beach, FlDecember 2000
Keith Legg 847-680-9420
Coat, no grindCoat, no grind
Sequence 1 - Make sure that HVOFdoes not cause embrittlement
ASTM F-519, Type 1a.2 75% NTS All experience shows HVOF does not cause
embrittlement Just makes sure
Keith Legg 847-680-9420
Sequence 2 - can H from other plating or stripping escape through HVOF?
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
1. Bright Cd plate1. Bright Cd plate
2. Strip center - no bake2. Strip center - no bake
3. Coat within 4 hrs, no grind3. Coat within 4 hrs, no grind
H2 fill
Does H2 escape?
Keith Legg 847-680-9420
Sequence 3 - How does environmental embrittlement compare with Cr?
CoatCoat
expose
Expose small area in notchExpose small area in notch
45% NTS Solutions - H2O and 5% NaCl Exposed notch should corrode and release H
Keith Legg 847-680-9420
Exposure of bare surface for Sequence 3
Exposure of notch - 90 sector CNC machine using rounded edge blade (RBK, Seattle)
Sample
Blade
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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)
Keith Legg 847-680-9420
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
Specimen Rc hardnessH 2015 52.0, 51.9, 51.9H 2494 52.1, 51.6, 52.2H 2567 51.8, 51.7, 51.9
Keith Legg 847-680-9420
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
93.5m3.68 mils
93.5m3.68 mils
243.1m9.57 mils
HVOF31
Keith Legg 847-680-9420
Embrittlement - summary
Table shows hours to failure (pass>200)
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
# samplesColumn # 1 2 3 4 5Pretest H load No No Yes YesTest environment Air Air Air AirHydrogen bake No Yes No YesGrind coating No No No NoNotch partly exposedLoad (% of NTS) 75% 75% 75% 75%Coatings:
None 9
>200>200>200
Hard chrome, 0.003” 6
0 (H1688)0
0.1
WC-Co, 0.003” 9
>200>200>200
6.14
7.8
>20077.2
129.1
WC-Co-Cr, 0.003” 9
>200>200>200
210.26.8
>200>200>200
Hard chrome, 0.010” 6
0.10.1
0 (H2511)
WC-Co, 0.010” 9
>200>200>200
10.72.84
0 (H1216)>200>200
WC-Co-Cr, 0.010” 9
>200>200>200
57.816.67.7
>200>200>200
Sequence 1 Sequence 2Baseline Hydrogen pre-test loading
Keith Legg 847-680-9420
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
0
100
200
Hours to failure
None Hardchrome,0.003”
WC-Co,0.003”
WC-Co-Cr,0.003”
Hardchrome,0.010”
WC-Co,0.010”
WC-Co-Cr,0.010”
Keith Legg 847-680-9420
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
Keith Legg 847-680-9420
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