The oxidation properties of the 2^nd-5^th generation Ni-base superalloys were investigated. Isothermal oxidation examination was performed at 1023, 1173 and 1373 K in air for up to 3.6×10⁶ s and the oxides were identified by using XRD analysis and SEM cross section observation.
   The 3^rd, 4^th generation superalloys and 5^th generation superalloy TMS-173 formed thick NiO layers at the surface caused by the outward diffusion of Ni at 1023 K. These alloys showed poor oxidation resistance at 1173 and 1373 K due to the spinel formation, except for the oxidation resistances of the 3rd generation superalloys at 1373 K which were slightly improved by forming Al₂O₃ layers under the spinel layers. The 2^nd generation superalloy and 5^th generation superalloy TMS-196 show excellent oxidation resistance at all temperatures examined in this study, forming Al₂O₃ protective layers. These favorable results were caused by their high Cr content.