Abstract:The growth.of oxide films on 476 alloy, with a small amount of additive elements such as Si etc., oxidized in wet hydrogen atmosphere is some times accompanied by the formation of a great many whiskers. Typical form of whiskers grown on the oxide film is of flag pole type with a globe on its top. The pole is a spinel single crystal oxide (Fe,Mn) Cr_O, and the globe is a metallic compound (Ni,Fe),Aly covered with protective AI, Si oxide layer. Nucleation of the metallic globe named white particle is formed at the early stage of heating between 700 C and 900 C.It seems to be extracted from the alloy matrix as a result of aluminium diffusion. Axial growth of pole begins at about 1 150.It is supposed that the whisker grows at the root of a white particle and the interaction effect between the stress of oxide around the particle and the climbing motion of dislocation beneath the particle. If the alloy surface is covered uniformly with CrZ03 as the inital oxide film, its final surface oxide film has no whiskers even after long time oxidation at higher temperature in hydrogen atmosphere.Proper surface treatment of base alloy> such  mechanical brushing, is very effective for the formation of Cr203 at initial stage.it is supposed that the brushed surface may be activated to produce surface reactions by an enrichment of lattice defects.

Key words: sealing alloy, oxide film, oxide whisker