Passive Films, Surface Structure and Stress Corrosion and Crevice Corrosion Susceptibility.
Abstract
Field ion microscopy (FIM) is capable of imaging defects such as sub-critical crack formation and growth, and surface rearrangements, and of detecting new surface phase formations, and other disturbances. Thus, we have used the technique to characterize various modes of hydrogen reactions with metal surfaces. Previous work from this laboratory has revealed examples of one mode, the initial crack formation and growth in the hydrogen-titanium and hydrogen-zirconium systems. In each case there were indications of preferential crystallographic attack producing cracks within the metal matrix approximately 10-15 atomic layers deep in the case of titanium, and 2-5 layers deep in the case of zirconium. In the present phase of the work, FIM was used to examine microscopic details of the initial stages of hydrogen interactions with some additional pure metals and metal alloys, i.e., niobrium, aluminum, 304 stainless ssteel and iron-24 wt. & chronium steel. The hydrogen-metal interactions occurred during the FIM imaging process with hydrogen pressures between ten to the minus 4th power and ten to the minus 6th power torr at metal temperatures between 20 and 80 K, and while the metal was subjected to stresses brought about by the electric field necessary for imaging the multifacted, approximately hemispherical metal surface. The method used involved comparison of micrographs obtained during inert gas imaging (neon, helim) with micrographs obtained in pure hydrogen or mixtures of hydrogen and inert gases.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1978
- Accession Number
- ADA078596
Entities
People
- A. J. Melmed
- J. J. Carroll
- J. J. Ritter
- J. Kruger
- J. R. Ambrose
Organizations
- National Institute of Standards and Technology