Characterization of surfaces by soft X-ray spectroscopy

Soft X-ray spectroscopy has important capabilities for investigating the surface region of metals and alloys. By calibrating the changes in the soft X-ray emission bands from both the metal and the oxygen, it is possible to determine the oxide thickness, the degree of oxidation, the element in the alloy with which the oxygen has combined, the relative amounts of alloying elements in the surface oxide, and the oxide state of a substrate metal that has a protective coating. For Ti-6Al-4V alloys there was an increase in surface oxygen after prebond treatment which was due to a change in the degree of oxidation rather than in oxide thickness, and the oxygen was combined with the titanium in the surface oxide. The oxygen K intensity distribution, from aluminum that was given a surface chromate treatment, showed that the oxygen is combined with the chromium. In Fe-Cr alloys there is an increase in the amount of chromium combined with oxygen relative to bulk chromium with decreasing chromium content. The oxide surface of steel with a 50 Å metal protective coating was reduced when the oxide of the protective metal coating had a heat formation greater than that of the iron oxide.