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Ultrasonic Characterization of Hydrogen Induced Stress in 4140 Steel

Don E. Bray, Ph. D., P. E.

Don E. Bray, Inc.

P. O. Box 10315

College Station, Texas USA 77842-0315

Voice/Cellular 979-492-9534

Email debray1@brayengr.com

http://brayengr.com

Northwest Houston Sub-section of the ASME

30 March 2010

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Setup for Present Experiments

1 2 3

Test Blocks

1 Control Block2 & 3 Test Blocks

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Hydrogen Flow out of Blocks

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Equations Governing Hydrogen Movement – Fick’s Second Law

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Experimental Procedures

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• Block 1 held in laboratory for comparison.

•Blocks 2 and 3 send to Honeywell for hydrogen

exposure

•Initial data obtained at intervals on blocks 2 and 3,

starting at 20 and 14 days after leaving autoclave,

respectively

•Experimental error ± 3 m/s.

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Summary of Results from Frequency Analysis

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1. Peak (fp) and low frequency (fa) groups shifted downward with hydrogen exposure.

2. No significant change after removal from autoclave.

Summary from Photomicrographs

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1. Decarburization at depth of 0.2 mm.

2. Decarburization layer less than 1.2 mm wavelength,

3. No effect expected on velocity due to decarburization.

Summary from Texture Analysis

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1. XRD showed texture differences for top and bottom surfaces.

2. Texture likely reason for velocity separation for tops and bottom sides.

3. Texture may be reason for differences in post autoclave velocity pattern with time.

Results of LCR2 Experiments

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1. LCR waves have been propagated on the opposite wall of flat plate.

2. More work should be done to excite the wave on inside curved wall of pipes and pressure vessels.

3. More work should be done to measure velocity on inside wall with required resolution.

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Conclusions

• Ultrasonic velocity change may be a reliable tool for measurement of reversible hydrogen buildup in metals.

• Further investigations with different conditions are underway.

Acknowledgements

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• The hydrogen environment was contributed by Honeywell Corrosion Solutions, Honeywell International, Inc., Houston, Texas.• Drs. Richard B. Griffin of TAMU Qatar and Malur Srinivasan of Lamar University contributed to the project.• Mr. Jonathan Dahmann collected and analyzed much of the data.