Classification of oxidation behavior of disilicides

This study focuses on classification of structures of oxide scales formed on disilicides. The oxide scales formed on disilicides can be grouped into 3 types, (a) silica scale, (b) mixed oxide (silica+metal oxide) scale, and (c) double layered (silica/metal oxide) scale. Disilicide that forms an oxide scale of the type (a) generally show excellent oxidation resistance. As such disilicides, there are FeSi2, COSi2, MoSi2, WSi2, etc. In FeSi2 and COSi2, a protective silica scale must be formed due to the selective oxidation of Si, whereas in MoSi2 and WSi2 evaporation of metal oxide plays an important role for the formation of a silica scale. Oxidation of TaSi2 and NbSi2 belonged to the type (b), and only CrSi2 the type (c).