Famous Failures: Hydrogen Embrittlement - Potential ...

Famous Failures: Hydrogen Embrittlement -

Potential Failure Cause on Plated Parts

Moderator

Melissa Gorris

Host

Rebecca Stawovy

Metallurgist

Host

Ben Schmidt

Metallurgist

FAMOUS FAILURES

FAMOUS FAILURES

Failure Analysis

Bell Helicopter Failure

Hydrogen Embrittlement

Contributing Conditions

How Does Failure Occur?

Prevention

NSL Failed Washer Analysis

What we’ll talk about today…

About NSL Analytical

NSL provides independent laboratory testing services to a diverse array of customers within

regulated end-markets, where testing speed, accuracy and consistency are mission

critical to operations.

Our teams of chemists, engineers and metallurgists provide scientific expertise in

materials testing with a focus on metals, alloys and technical ceramics that are utilized

in critical end market applications.

Spectroscopy Thermal AnalysisMetallurgical /

Failure Analysis

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Testing

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Spectrometry

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CharacterizationMicroscopy

© 2021 NSL Analytical Services, Inc. All rights reserved

Failure Analysis

• Get background information

• Do non-destructive testing

• Do destructive testing

• Draw conclusions

• Provide documentation

From ASM International, Metals Handbook, Desk Edition, Second Edition, J.R. Davis, Editor, p.1203


Why is Hydrogen Embrittlement Important?

• Attributed to sudden, catastrophic failure

• Well below expected load capacity

• Delayed fracture

• Little macroscopic yielding – microplasticity only

• Difficult to detect and prevent

• Still an active area of research


Famous Failure:

Case Studies –


What Happened?

• June 2, 2010

• Midlothian, Texas

• Bell Helicopter BELL 222 N515MK

• Helicopter had been in service for

several years, and had undergone

repairs

Photo taken from:

https://www.ntsb.gov/_layouts/NTSB/OpenDocument.aspx?Document_DataId=40353991&FileName=Photo 1 - Photo

Showing First Responders on-scene (Midlothian Fire Department Photo)-Master.PDF


What Happened (cont.)

• Fractures in several locations

around the rotor head/rotor

control system

• A side drive pin was not

attributed as overload alone.

2. NTSB Report No. 11-013



• View of some of the

rotor components

• Drive pins inside

swashplate assembly

2. NTSB Report No. 11-013© 2021 NSL Analytical Services, Inc. All rights reserved


• The A side pin fractured where

the head met the shank

• NTSB investigation of failure

• Failure likely due in part to

hydrogen embrittlement

Intact B Side Pin

Recovered head of

fractured A Side Pin2. NTSB Report No. 11-013


NTSB Investigation

• Did not fail due to overload alone

• Determined to be Cd plated part by

EDS, chemistry checked between

pins using handheld XRF

• Several cracks observed

• Hardness was approximately 51

HRC



NTSB Investigation (cont.)

• Magnified view of

radial cracking

• Area where pin contacted

the outer ring visible

– Cd plating partially worn




• Small areas of dimpled

fracture surface

• Significantly higher

hydrogen content in pin




• Torque test of the material’s

susceptibility

• Plating stripped, reheat treated,

aged, pickled, and plated

• Similar fracture surface: brittle,

small areas of dimples



NTSB Investigation Takeaways

• Conditions were right for internal reversible hydrogen embrittlement to occur

• Typical indicators of hydrogen embrittlement were present

• Drive pin was shown to be susceptible to embrittlement when improperly processed

Photo taken from:

https://www.ntsb.gov/_layouts/NTSB/OpenDocument.aspx?Document_DataId=40353990&FileName=Photo 2 -

Main Wreckage (FAA Photo)-Master.PDF


Hydrogen Damage

• Hydrogen Induced blistering

• Internal Hydrogen Precipitation

• Hydrogen Attack

• Hydride Formation

• Hydrogen Embrittlement

ASM Handbook, Volume 13B, Corrosion: Materials, Stephen D Cramer

and Bernard S Covino, Jr editors, 2005.

Hydrogen Blister


Hydrogen Embrittlement – Identification

Susceptible

Material

Hydrogen

Embrittlement

Stress

Hydrogen Source


Hydrogen Embrittlement – Identification (cont.)

Susceptible Materials

• Steels

– High strength: 130-180 ksi minimum

– Hardness: 35-40 HRC minimum

• Stainless Steel

– Typically, cold worked or martensitic

• Nickel Alloys

• Titanium

• Refractory Metals

ASM Handbook, Volume 23, Materials for Medical Devices, Roger J

Narayan editors, 2012.



Hydrogen Source

• Plating operations

• Hydrogen storage

• Welding

• Heat Treating atmosphere

• Pickling (Cleaning)

Stress

• Applied

• Residualhttp://demo.premiersteels.in/components/wp-

content/uploads/2020/04/infrastructure-1.jpg



• Appears brittle at low magnifications, small isolated pockets of dimpled fracture surface

• Cracks originate internally, intergranular in high strength steels


Hydrogen Embrittlement – Mechanism

• Hydrogen embrittlement typically

affects high strength and heavily

cold worked steels which have a

body centered cubic structure.

API 571 Section 5.1.2.3


Hydrogen Embrittlement – Mechanism (cont.)

H

Atomic Diameters• Hydrogen: 0.074 nm

• Carbon: 0.154 nm

• Iron: 0.252 nm

C

Fe



Hydrogen induced decohesion

(HID)

• Hydrogen acts to loosen the

molecular or atomic bonds.

• Crack propagation can occur

more easily

• Also called Hydrogen Enhanced

Decohesion (HEDE)



Hydrogen Enhanced Local

Plasticity (HELP)

• Hydrogen enhances the movement

of dislocations within grains.

• Increased localized deformation



Hydrogen Enhanced

Strain Induced Vacancy

Formation (HESIV)

• Vacancies nucleate, grow

and link together.



Hydrogen Induced Phase Transformation (HIPT)

• Formation of brittle hydrides at the the crack tip

• Austenite to martensitic phases in 304 Stainless

https://www.researchgate.net/figure/Schematic-diagrams-of-HE-mechanisms-a-HIPT-64-hydrogen-induced-

phase-transformation_fig5_340851994 © 2021 NSL Analytical Services, Inc. All rights reserved

Hydrogen Embrittlement – Current Research

Argonne National Labs• Using HEXD (High Energy X-Ray

Diffraction)

• 4130 Steel Samples were cyclically stressed in either air or a hydrogen environment.

• HEXD data indicated that in the sample tested in air, dislocations were evenly dispersed.

• In the sample tested in H2, dislocations had migrated to grin boundaries.

Matthew Connolly1*, May Martin1, Peter Bradley1, Damian Lauria1, Andrew Slifka1, Robert Amaro2, Christopher

Looney3, and Jun-Sang Park4, “In situ high energy X-ray diffraction measurement of strain and dislocation density

ahead of crack tips grown in hydrogen,” Acta Mater. 180, 272 (2019). DOI: 10.1016/j.actamat.2019.09.020


https://www.sciencedirect.com/science/article/pii/S135964541930610X

Hydrogen Embrittlement – Current Research (cont.)

Imaging Methods – determining

where the hydrogen is located• Atom Probe Tomography (APT)

• Combines field ion microscope

with a mass spectrometer

• Secondary Ion Mass Spectrometry

APT Output


Hydrogen Embrittlement – Mitigation

Hydrogen “Bake Out”

• This method involves heating

the material to an elevated

temperature for a sufficient time

to allow the hydrogen to diffuse

out of the material.

• Typical temperatures:

400°F - 800°F.

https://www.kleinplating.com/uploads/metal-heat-treatment-and-

baking-parts-klein-plating-works-chart.jpg


Hydrogen Embrittlement – ASTM Methods

• ASTM F519 – Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation

of Plating/Coating Processes and Service Environments

• ASTM F1624 – Standard Test Method for Measurement of Hydrogen Embrittlement

Threshold in Steel by the Incremental Step Loading Technique

• ASTM A143 – Standard Practice for Safeguarding Against Embrittlement of Hot Dip

Galvanized Structural Steel Products and Procedure for Detecting Embrittlement

• ASTM F1940 – Standard Test Method for Process Control Verification to Prevent Hydrogen

Embrittlement in Plated or Coated Fasteners

• ASTM F2660 – Standard Test Method for Qualifying Coatings for Use on F3125 Grade

A490 Structural Bolts relative to Environmental Hydrogen Embrittlement


The

Failure Analysis

Lab Experiment:

Washer Failure

Experimental – Washer Failure

• Questions to Ask:

– Is the part broken?

– Was there noticeable deformation?

– Was the part in service for over a

week?

– Was the part plated or coated with iron

or zinc phosphate?

– Was the part acid cleaned?

– Is the hardness over 40 HRC?

– Did the part break due to a sudden

impact load?

– Was the material heavily cold worked?

Taken from ASM Handbook, Volume 11, Failure Analysis and

Prevention, B. Miller, R. Shipley, R. Parrington, D. Dennies,

editors.


Experimental – Washer Failure

• Material: AISI 1055 steel

• Hardness: approx. 48 HRC

• Hydrogen Source:

Zinc Phosphate Plating

• Fracture Surface: mixed

intergranular/ductile failure with

grain boundary separation


FAMOUS FAILURES

Summary

Failure Analysis



Contributing Conditions

How Does Failure Occur?

Prevention

FAMOUS FAILURES

References1. ASM Handbook Vol. 11: Failure Analysis and Prevention. Hydrogen Damage and

Embrittlement. Pg. 809. ASM International, 2002.

2. Materials Laboratory Factual Report. Report No. 11-013. National Transportation

Safety Board, March 14, 2011. URL:

https://www.ntsb.gov/_layouts/NTSB/OpenDocument.aspx?Document_DataId=403456

95&FileName=Materials Laboratory 15 - Factual Report 11-013-Master.PDF.


FAMOUS FAILURES

Q&A

Ben Schmidt

MetallurgistRebecca Stawovy

Metallurgist

Dave Kovarik

Metallurgist

Failure Analysis

Consultant

John Ratka

Director,

Metallurgical

Operations

FAMOUS FAILURES

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Benjamin Schmidt

Metallurgist

[email protected]

216-438-5201

Rebecca Stawovy

Metallurgist

[email protected]

216-438-5235

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