ultrasonic characterization of hydrogen induced stress in 4140 steel iopf2010-6001
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IOPF 2010
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
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IOPF 2010
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.
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Setup
1 2 3
Test Blocks
1 Control Block2 & 3 Test Blocks
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LCR Wave
Frequency = 5 MHz Wavelength = 1.2 mm
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Hydrogen Flow from Blocks
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Equations Governing Hydrogen Movement – Fick’s Second Law
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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.
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fp = peak frequency fc = central frequency
fa = low half power point fb = upper half power point
Frequency Analysis
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Results of Frequency Analysis
X
X – a likely anomaly
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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.
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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.
4. No hydrogen induced cracking found.
Specimen 3
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Summary from Texture Analysis
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0
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.
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LCR2 Excitation on Opposite Wall
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LCR2 Arrivals at 75 and 150 mm probe spacing on 15 mm plate
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150 mm
75 mm
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Conclusions
• LCR velocity change may be a reliable tool for research and application in measurement of reversible hydrogen buildup in metals.
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Acknowledgements
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• 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.
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