Análisis de las capas de alumina formadas a elevada temperatura sobre aleaciones MCrAIy y barreras térmicas

Résumé

The effect on M (Ni, Fe, Co)CrAlY manufacturing process (ODS or wrought alloys), alloy composition, substrate thickness and oxidation conditions on the alumina scale morphology, composition and growth kinetics during oxidation at temperature range of 900 -1200 C has been studied under the objective of: - Alloy oxidation behaviour and alumina scale phases transformation, including microstructure examination of the oxide surface scale, thermogavimetry studies and oxide scale characterization. - I n detailed evaluation of the residual stresses state. The FeCrAlY alloys studied involves homogeneous and exclusive alumina scale formation, where the experimental results and later analysis and discussion is applying on NiCrAlY alloys which exhibi ts complex oxidation behaviour. Ni based alloys exhibits heterogeneous alloy microstructure and mixture of oxide scale composition, mainly formed by alumina scale together with Chromium, Nickel and Cobalt oxides, function of alloy composition. The applied experimental techniques and conclusions on oxides scales formed on the surface of prior alloy systems studied are used as background to investigate and understanding of TBC system. NiCoCrAlY layer is a bond coat (BC) materials in TBC system, where the buried alumina scales (Thermally Growth Oxide, TGO layer) growths under ceramic layer YSZ (Ytrium oxide Stabilized with Zirconia layer, ZrO2-8 Y2O3). Model TBC standard samples and gas turbine blade components experimental results and ana lysis interpretation, are focused into the progression of damage and failure indications. The experimental activities was aimed to detect premature failure and evaluate sample integrity by Ruby Fluorescence Spectroscopy. Therefore, various microstruc tures features as function of thermal cyclic (1000 C in air flow) and intermittent oxidation (1100 -1200 C) have been carried out. We call it intermittent oxidation to isothermal oxidation during certain period of time and cooling to room temperature . Then the sample in visual inspected looking for any kind of surface damage and RFS analysis (this process got no more than 24 hours). Then the sample is again oxidize at same conditions.