Keith Legg Hydrogen Embrittlement Testing HCAT Program Review Cocoa Beach, Fl December 2000

Keith Legg Coat, no grind Sequence 1 - Make sure that HVOF does not cause embrittlement ASTM F-519, Type 1a.2 75% NTS All experience shows HVOF does not cause embrittlement  Just makes sure

Keith Legg 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 plate 2. Strip center - no bake 3. Coat within 4 hrs, no grind H 2 fill Does H 2 escape?

Keith Legg Sequence 3 - How does environmental embrittlement compare with Cr? Coat expose Expose small area in notch 45% NTS Solutions - H 2 O and 5% NaCl Exposed notch should corrode and release H

Keith Legg Exposure of bare surface for Sequence 3 Exposure of notch - 90  sector  CNC machine using rounded edge blade (RBK, Seattle) Sample Blade

Keith Legg 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 Base material Expected NTS 260 ksi  Tested at 362,416 to 382,521, average = 373,600 ksi  Sequence 1 and 2 testing at ksi Rockwell hardness

Keith Legg 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 93.5  m 3.68 mils 93.5  m 3.68 mils  m 9.57 mils HVOF 31 

Keith Legg 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

Keith Legg 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

Keith Legg Embrittlement - Sequence 2, not baked No immediate failures Need to acquire uncoated baseline Baking removes most H 2 Not completely removed in WC-Co One immediate failure WC-CoCr 0.010”  Being analyzed at Boeing

Keith Legg 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 H 2 removal by flame?  Reduced Kt?  Bake removes H 2 from most samples  Except WC-Co why?  Immediate fail WC-Co 0.010” being examined at Boeing  Baseline uncoated (i.e. coated and stripped) being acquired