On the dependence of composition and depth profiles of stainless steel and inconel surfaces on pretreatment

Pretreatment methods influence the surface properties of the wall materials used in fusion devices. In particular the vacuum properties and the impurity release to the plasma may depend to a large extent on the pretreatment before and after the assembly of the components. Using combined Auger/X-ray microanalysis together with sputter-etching, the surface and in-depth-composition of SS 304 and Inconel 600 samples were determined after the following treatments: chemical-etching, corundumblasting, polishing, and local melting in a protective atmosphere (simulation of welds). The impurity concentration near the surface (mainly O and C) are noticeably influenced. After welding, the composition of the surface-near region is strongly, changed down to several 100 nm. Near the surface some of the major alloy constituents are replaced by the minor ones. (Al and Ti in Inconel 600, Cr in SS 304). As the total surface of welded joints in fusion devices is not negligible, these effects have to be considered