  The diffusion-controlled growth and microstructural evolution at the
interface of aluminide coatings and different substrates such as Ni-base
superalloys and steel are reviewed. Quantitative diffusion analysis indicates
that the diffusion rates of components in the beta-NiAl phase increases with
the addition of Pt. This directly reflects on the growth rate of the
interdiffusion zone. The thickness and formation of precipitates between the
bond coat and the superalloys increase significantly with the Pt addition.
Mainly Fe2Al5 phase grows during hot dip aluminization of steel along with few
other phases with very thin layer. Chemical vapor deposition process is being
established for a better control of the composition of the Fe-aluminide coating
on steel.
