MODELING AND SIMULATION OF OXIDATION OF COATINGS ON SUPERALLOYS

Abstract

In the present work a study has been undertaken to understand the kinetics of cyclic oxidation process in superalloys, review the models available and check if these models can be applied to model the oxidation process of the coatings on superalloys. AICrN based PVD coated samples of Superni 76 substrate were used. Cyclic oxidation tests in air environment and molten salt (Na2SO4.60%V205) salt environment were carried out at 900°C for 100 cycles. The parabolic scaling constant K, Cm, (L\W/A)max and C. were calculated on the weight change data. Various models were considered, used for efficiently modeling the cyclic oxidation process. Cyclic oxidation spalling program (C.O.S.P) was chosen for the air oxidation process. Cm, (AW/A)max and C0 were used as inputs for the model and K and Wm values was calculated using the model. The K value calculated by the inverse square method and Wm value calculated from the weight change curve were used for validating the model. Interfacial Spallation model was chosen for the modelling of cyclic oxidation process in the molten salt environment. K and FA were used as the inputs for the model and a curve between specific weight change and number of cycles was plotted using the model. The curve generated experimentally was matched with the theoretical curve and hence the model was validated.