The nondestructive evaluation of hydrogen in metals and alloys is a major challenge with significant impact for the prevention of catastrophic failure in critical engineering structures. Radiography using neutrons has previously exploited the large neutron-hydrogen cross section to visualize corrosion products and moisture in metals; however, the method is limited due to the effective averaging of the hydrogen density over the entire particle path length; thus, internal details may be hidden in thick components. We have developed a neutron tomographic imaging system specifically for the detection of hydrogen and utilized the system to study component failures in jet aircraft engines. In several recent accidents, failure of engine components, namely the titanium compressor blades have been implicated as contributing to the accidents. Previous destructive methods of quantifying hydrogen in the blades indicated hydrogen concentrations of approximately 500 ppm were present and may have contributed to the unexpected failures. We used neutron tomography to characterize the blades non-destructively and detected local hydrogen concentrations in the range of 1,000 to 7,000 ppm in spatially heterogeneous distributions. Scanning electron microscopy, x-ray diffraction and mass spectrometry were utilized to validate the findings. In addition, it was discovered that the hydrogen detected was not hydride as previously thought; but rather, interstitial or trapped hydrogen. These results demonstrate a significant role for neutron tomography in the detection of hydrogen in critical aircraft components and point toward applications in other areas where hydrogen embrittlement is known to be a major problem such as in the pipe systems of petro-chemical and nuclear plants.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Advanced Materials|
|State||Published - Apr 1995|
ASJC Scopus subject areas
- Materials Science(all)