Autoradiographic Technique for Studying the Segregation of Hydrogen Absorbed into Carbon and Low Alloy Steels

Previous studies have been conducted by using tritium to identify the areas to which hydrogen segregates in steels. Most of these studies were conducted with stainless alloys or steels coated with barrier films on the surface to avoid the loss of optical resolution due to the formation of corrosion products from the processing. The technique described in this paper preserves the microstructural features of the easily corroded carbon and low alloy steels without the need for protective films by inhibiting the photographic processing solutions with sodium nitrite. Tritium segregation can then be directly related to the microstructural features of a metallographically polished and etched specimen by observing the resulting silver clusters with a scanning electron microscope, equipped with automatic image analysis, up to magnifications of 10⁴ diameter. Examples are presented by using a quenched and tempered casing steel showing tritium segregation to: (1) manganese-sulfide inclusions, (2) glassy silicate particles, and (3) globular aluminum oxide inclusions.