AlSiY coating was deposited on the directionally solidified DZ22 superalloy using an arc ion plating technique in an aim to resolve or alleviate the high temperature corrosion damage of high pressure turbine blades for aero-engines and gas turbine engines. The attained results demonstrate that the AlSiY coating deposited and vacuum diffusion heat treated at a high temperature consists of an outer

an intermediate and a thin inner diffusion layer

which is typical of a high activity aluminide diffusion coating composed of the single β–NiAl intermetallic phase. The results of thermogravimetric analyses and examinations of cross sections demonstrated that the wet gr

it blasting process improves significantly the corrosion resistance of the AlSiY coating under salt film and hot-gas conditions. A thick oxide scale developed on the as-diffusion heat treated coating consists primarily of Al

2

O

3

and NiAl

2

O

4

corrosion products under salt film and hot-gas corrosion conditions

and most of the coating degenerated into the γ′–Ni

3

Al phase with some pores formed inside. Wet grit blasting of the heat treated AlSiY coating is desirable to promote the selective oxidation of aluminium

chromium elements and formation of a thin

denser alumina scale under both corrosion conditions

thereby enhance remarkably the high temperature corrosion resistance and prolong the service life of the arc ion plated AlSiY coating.