Cyclic Oxidation Behaviour of Single-Crystal Ni-Based Superalloy Containing Rhenium in Air at 900 ℃

By means of SEM,XRD and EDAX,the high temperature cyclic oxidation behavior of the single-crystal Ni-base superalloy containing rhenium at 900 ℃ in air was investigated.Results show that the initial oxidation rate is large,and the weight loss and gain occurs alternately in the different stages of the oxidation;the oxidation kinetics does not obey parabolic law.An obvious outside oxidation and internal oxidation occurs during the high temperature oxidation.After oxidized at 900 ℃,three oxide layers form in the alloy including the outer layer consists of NiO,Al2O3 and(Ni,Co)Cr2O4 phases,middle layer consists of CrTaO4 and AlTaO4 phase,and the internal oxidizing layer is identified as Al2O3 phase.During the oxidizing process of the alloy,the phases that are rich in Ta,Re and W may restrain the element Al in the matrix from diffusing outward,which restrains the growth of the oxide layers so as to decrease the oxidizing rate of the alloy.