| With the increasing of energy demand and requirement for environment protection, it is one of valid choices to increase the energy conversion efficiencies through improving turbines gas inlet temperatures. And now turbine operating temperature will increase to be 1000℃or higher on the basis of industrial safety and longer turbine lifetime. From the level of technology development now, Pt-modified aluminide coating is one of possible coatings that lifetime can be achieve to 25000h when operating temperature is 1000℃or even higher. However, complicated influence between Pt and other elements in bondcoats and different oxidation characters of bondcoat result different coatings oxidation resistance and TGO adherence for Pt-modified aluminide coatings, especially the detailed TGO growth mechanism is still conflict till today. And few research on Pt-modified aluminide coatings early stage oxidation and final failure for TBC system which the lifetime achieves to 25000h could be found.To realize the Pt-modified aluminide bondcoats microstructure, alumina rumpling and stress development during oxidation, factors such as temperature, oxidation time period and coating surface treatment have been studied in this paper. Pt content effect, rumpling of TGO, residual compressive stress in TGO and TGO growth mechanism, the experimental surface treated for low-aAl and high-aAl coatings were performed at different temperature and cyclic time. TGO thickness and Phase transformation in NiPtAl bondcoat are responsible for TGO failure during cyclic oxidation at 1100℃. And details for stress growth trend and influence factors to stress are also been studied.NiPtAl bondcoat microstructure, morphology and phase transformation have been studied by using optical microscope and scanning electron microscope. Tracer 18O2 isotope was utilized to study the alumina growth mechanism. To analysis elements composition profile and Pt content influence, Secondary Neutral Mass Spectrometry (SNMS) was used, and then using Raman spectroscopy to measure stress in alumina. On basis of about 30000h high temperature oxidation for 150 pieces of NiPtAl coating specimens, TGO rumpling and spallation were anlysised, and obtained the following important conclusions: (1) Stable and compact alumina formed on the surface of two kinds of Pt modified aluminide bond coats during oxidation at high temperature. And the two coatings could be used as bond coat for thermal barrier coating due to thermally grown oxide alumina which showed excellent anti-oxidation and adherence properties.(2) Al, Ni, and Pt etal. elements composition in bondcoat changed after oxidation has been studied by using scanning electron microscopy (SEM/EDX) and other equipment. It was found that elements diffusion in bondcoat resulted phase transformation. Although PtAl2 is not stable phase at high temperature high content (atomic 10%) Pt induced longer TBC lifetime.(3) Oxidation temperature showed larger influence to thermal barrier coating lifetime. The failure TGO thickness in two kinds of TBC system which used in the experiment existed, about 6～8μm. The relationship about TGO thickness as a function of time obtained for TBC system and single-NiPtAl BC system.(4) Ceramic layer could suppress TGO rumpling for TBC samples, and polished coating and isothermal oxidation condition to make smaller TGO rumpling was found by surface profile.(5) TBC failure interface in the experiments was always TGO/BC interface. And through the experiment study it makes sure that TGO rumpling induced stress and TGO failure thickness were initial reason to TBC failure.(6) The TGO residual compressive stress for low-αAl and high-αAl coatings after oxidation was investigated through Raman/luminescence spectroscopy. High-αAl coatings in TBC stress was little higher than low-αAl coating. No-polished, polished and TBC ceramic deposition etal.coating treatment showed larger influence to TGO growth and stress value.(7) According to alumina failure critical thickness, alumina thickness as a function of time, residual stress as a function of time andγ'-Ni3Al influence to alumina spallation, we explained alumina failure mechanism and suggested one mechanical model for alumina spallation during experiment at 1100℃, which would give improvement for optimizing and evaluating the coating lifetime numerical model.
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