SIMS study on carburisation and decarburisation of superalloy

SIMS analysis was performed for superalloys (Inconel 617) corroded in high temperature helium gases. From the ion images and the chemical analysis of carbon, the following points were proved. (1) In high carburising helium, the carburisation was limited to near the surface (about 40 μm from the surface), and the surface precipitate of carbide consisted of molybdenum carbide and silicon carbide. (2) Even under a decarburisation environment carbon and silicon were enriched in the same area as that of the oxide surface scale, though no molybdenum carbide was precipitated. (author)