Abstract: The NiCrAlY coatings were produced on a Co-based high-temperature alloy substrate by arc ion plating and annealed under vacuum conditions.The phase and the cyclic oxidation behavior of the cast alloy and the deposited coatings were investigated at 1 000 ℃ by using XRD,SEM and EDS technologies.It is shown that the deposited NiCrAlY coating,which consisted of a three-phase mixture:γ-Ni,γ′-AlNi3 and β-NiAl phase,have a homogeneous elemental distribution.After vacuum heat treatment,the grains in the coatings become much larger,the deposited NiCrAlY coating mainly consiste of γ-Ni,γ′-AlNi3,β-NiAl,α-Cr and trace of Cr23C6.The deposited coating surface forms Al2O3 scale during the cycles,and the Al2O3 scale is still perfective after 100 cycles.The deposited NiCrAlY coating after vacuum heat treatment forms α-Al2O3 much earlier and the α-Al2O3 scale has a better adherence to the NiCrAlY coating.Therefore vacuum heat treatment improves the oxidation resistance of arc ion plated NiCrAlY coating.