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Ultrasonic Characterization of Hydrogen Induced Stress in 4140 Steel IOPF2010-6001

Ultrasonic Characterization of Hydrogen Induced Stress in 4140 Steel IOPF2010-6001. Don E. Bray, Ph. D., P. E., Don E. Bray, Inc. PO Box 10315, College Station, Texas 77842-0315 debray1@brayengr.com http://brayengr.com

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Ultrasonic Characterization of Hydrogen Induced Stress in 4140 Steel IOPF2010-6001

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  1. Ultrasonic Characterization of Hydrogen Induced Stress in 4140 Steel IOPF2010-6001 • Don E. Bray, Ph. D., P. E., Don E. Bray, Inc. PO Box 10315, College Station, Texas 77842-0315 debray1@brayengr.com http://brayengr.com • Richard B. Griffin, Ph. D., P. E. TAMU Qatar Mechanical Engineering Program Doha, Qatar 10/21/10

  2. Basis for LCR Experiments • Assumption is that the block is fully charged with hydrogen in the autoclave. • Chemical change to other forms of hydrogen or other chemistries is ignored. • Upon removal of the block and returning to room temperature, shrinkage occurs, putting the outer surface in compression as the hydrogen escapes from the block.

  3. Setup Test Blocks 1 2 3 1 Control Block 2 & 3 Test Blocks 10/21/10

  4. LCR Wave Frequency = 5 MHz Wavelength = 1.2 mm

  5. 10/21/10

  6. Hydrogen Flow from Blocks 10/21/10

  7. Equations Governing Hydrogen Movement – Fick’s Second Law 10/21/10

  8. 10/21/10

  9. Experimental Procedures • Blocks 2 and 3 sent to Honeywell for hydrogen exposure. • Block 1 held in lab as control block. • Data obtained on blocks 1, 2 and 3 starting 20 and 14 days after leaving autoclave. • Data plotted as velocity differences (2-1 and 3-1). • Experimental error ± 3 m/s. 10/21/10

  10. 10/21/10

  11. 10/21/10

  12. Frequency Analysis fp = peak frequency fc = central frequency fa = low half power point fb = upper half power point

  13. Results of Frequency Analysis X X – a likely anomaly 10/21/10

  14. Summary of Results from Frequency Analysis Peak (fp) and low frequency (fa) groups shifted downward with hydrogen exposure. No significant change after removal from autoclave. 10/21/10

  15. Summary from Photomicrographs Specimen 3 Decarburization at depth of 0.2 mm. Decarburization layer less than 1.2 mm wavelength, No effect expected on velocity due to decarburization. No hydrogen induced cracking found. 10/21/10

  16. Summary from Texture Analysis XRD showed texture differences for top and bottom surfaces. Texture likely reason for velocity separation for tops and bottom sides. Texture may be reason for differences in post autoclave velocity pattern with time. 3/28/10

  17. LCR2 Excitation on Opposite Wall

  18. LCR2 Arrivals at 75 and 150 mm probe spacing on 15 mm plate 150 mm 75 mm 10/21/10

  19. Conclusions • LCR velocity change may be a reliable tool for research and application in measurement of reversible hydrogen buildup in metals. 10/21/10

  20. Acknowledgements • The hydrogen environment was contributed by Honeywell Corrosion Solutions, Honeywell International, Inc., Houston, Texas. • Dr. Malur Srinivasan of Lamar University contributed information on the texture difference between the two sides of the blocks. • Mr. Jonathan Dahmann collected and analyzed much of the data. 10/21/10

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