Ultrasonic detection of hydrogen attack in low alloy steels
Book
·
OSTI ID:86124
- Non-Destructive Inspection Co., Ltd., Osaka (Japan)
The objective of this study is to predict the early stage of hydrogen attack by means of ultrasonic technique and to correlate the variations in ultrasonic characteristics to the deterioration in mechanical properties, residual hydrogen and microstructural changes (methane bubble formation, decarburization and microcrack formation). On the specimens served at high pressure, high temperature hydrogen atmosphere, non-destructive ultrasonic detection of degradation by hydrogen attack has been performed. The bottom reflected ultrasonic rf pulses from 2,500 points of 50 square mm area in the specimens were collected as digitized rf waves through 100 MHz A/D converter. The variation in wave characteristics resulted from the dispersion of materials can be revealed in the power spectrum of traversed wave in frequency domain and can be defined as characteristic feature values such as center frequency, peak frequency, moment and skewness of Spectrums. Variation in the ultrasonic ``signature`` in time domain and frequency domain given by spectrum analysis due to hydrogen attack has been examined. Based on the knowledge that cavitation in material affects ultrasonic attenuation and velocity, frequency dependent ultrasonic attenuation and velocity have been examined to obtain the size and the number of cavities by using multiple scattering theories and the results have been ascertained by metallographic observations. The results obtained demonstrate that the measurements of frequency dependent ultrasonic attenuation and velocity have a strong potential to quantitative predictions of the methane bubble formation.
- OSTI ID:
- 86124
- Report Number(s):
- CONF-9505104--; ISBN 0-87170-548-6
- Country of Publication:
- United States
- Language:
- English
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