Wyniki wyszukiwania - Biblioteka Nauki

1

Protective coatings for high temperature applications.

100%

Singheiser L. , Quadakkers W. J. , Clemens D. , Steinbrech R. W.

|

tom R. XIX, nr 4

955-962

EN

The improvement of efficiencies of land based gas turbines requires a significant increase of gas inlet temperature. This results in an increased service temperature of the blading materials and consequently to an enhanced oxidation attack of the blade coatings, which are usually of the NiCoCrAlY type. These coatings can act as protection against oxidation/corrosion and as bond coats for zirconia based thermal barrier systems. In both applications slow growth rates and optimum adherence of the alumina scales forming on the NiCoCrAlY coating during high temperature service are of crucial importance for component life. The mentioned technologically relevant properties of the alumina scales not only strongly depend on the coatings base composition but also on the presence of minor and trace elements. In the present paper this will be illustrated by showing as examples the effect of minor changes in yttrium and titanium content on MCrAlY oxidation properties. The coatings were tested by cyclic oxidation in the temperature range 950 degrees centigrade - 1100 degrees centigrade. The effect of the composition variation was studied by characterisation of the bulk coating and the corrosion products using light and electron optical microscopy as well as dilatometry.

2

Microstructure and phase distribution of MCrAlY coatings.

88%

Penkalla H. J. , Wosik J. , Clemens D. , Quadakkers W. J. , Singheiser L.

|

tom R. XIX, nr 4

982-985

EN

For the protection of turbine blade materials against oxidation, coatings of the MCrAlY type are applied. The oxidation resistance of these multiphase coatings relies on protective alumina scales which are formed on the coating surface at high service temperatures of about 900 degrees centigrade, and is strongly affected by the phase distribution and composition. In the present study the coating material MCrAlY is investigated by means of transmission electron microscopy (TEM) whereby the chemical composition of the elements Ni, Co, Cr, Al, Re and Y was analysed systematically by EDX elemental mapping. In order to describe the phase distribution and composition in a single image a special method for the evaluation of the EDX elemental maps by statistical methods combined with image analysis were applied and described in this paper.

3

Quantitative characterisation of alumina scales on high temperature alloys by atomic force microscopy.

88%

Czyrska-Filemonowicz A. , Szot K. , Wasilkowska A. , Breuer U. , Quadakkers W. J.

|

tom R. XIX, nr 4

1141-1146

EN

The formation of thin oxide films on {111} and {110} single crystal specimens of the Fe20Cr5Al based ODS alloy during the early stages of oxidation at temperatures up to 1000 degrees centigrade was quantitatively investigated by atomic force microscopy (AFM). The AFM results revealed the crystalline character of corrosion layer. The alumina scale morphology (height and grain size of crystallites) was slightly dependent on the crystallographic texture of the underlying bulk material. The results showed that AFM is promising technique for the quantitative characterization of the surface structure of oxide layers in the initial stages of oxidation processes.

4

The influence of silver addition on the microstructure and oxidation behaviour of gamma-TiAl based alloys

75%

Gil A. , Niewolak L. , Czyrska-Filemonowicz A. , Penkalla H. J. , Shemet V. , Singheiser L. , Quadakkers W. J.

|

tom R. XXII, nr 4

341-344

EN

The aim of this study was to investigate how the beneficial effect of silver addition on the oxidation behaviour of TiAl alloys is correlated with changes in the alloys microstructure. For this purpose the microstructures of the following alloys were compared: Ti-50Al (full lamellar), Ti-50Al (duplex), Ti-48Al-2Cr and Ti-48Al-2Ag. The results showed that silver addition stabilises the gamma-TiAl phase formation at the expense of alpha2-Ti3Al phase.

PL

Celem pracy było zbadanie, czy korzystny wpływ dodatku srebra na wysokotemperaturowe utlenianie stopów TiAl jest wywołany zmianami w mikrostrukturze tych materiałów. W tym celu porównano mikrostrukturę następujących stopów: Ti-50Al, Ti-50Al-2Cr i Ti-50Al-2Cr. Potwierdzono, że dodatek srebra stabilizuje fazę gamma-TiAl i eliminuje fazę alfa2-Ti3Al.