Wyniki wyszukiwania - BazTech

1

Water vapour effect on high temperature oxidation behaviour of superalloy Rene 80

Nowak W. J., Wierzba P., Naumenko D., Quadakkers W.J., Sieniawski J.

Advances in Manufacturing Science and Technology

|

2016

|

Vol. 40, nr 2

41--52

EN

The commercial Ni-base superalloy Rene 80 was isothermally oxidized at 1050°C in synthetic air and synthetic air with addition of H2O in two types of experiments: during oxidation in a thermobalance for 50 h and during oxidation in a tube furnace. During thermobalance oxidation the water vapour content was 7% while during tube furnace oxidation 20%. The samples were exposed up to 100 hours. The obtained results revealed that Rene 80 formed the oxide scale consisting of TiO2 and Cr2O3 in the outer and BCrO3 in the inner part of the oxide scale. Below the latter oxides internal Al2O3 precipitates are visible. Such an oxide scale morphology was observed on samples exposed in both atmospheres. For material oxidised in dry synthetic air an additional phase, namely TiN below the zone of internal oxidation of aluminium was found for all of the times. The internal TiN phase was supressed due to the presence of water vapour in the atmosphere. The obtained results showed that such a suppression is observed up to at least 100 hours.

PL

W pracy przedstawiono wyniki badań kinetyki procesu utleniania wysokotemperaturowego nadstopu niklu Rene 80 w temperaturze 1050°C i w czasie 100 h, w środowisku syntetycznego powietrza z i bez dodatku pary wodnej. Do utleniania stosowano dwa rodzaje pieców: komorowy – próba termograwimetryczna i piec rurowy. Przyjęto zawartość pary wodnej w powietrzu syntetycznym podczas próby w komorze termograwimetrycznej – 7%, natomiast w piecu rurowym 20%. Analiza wyników badań składu chemicznego metodami emisyjnej spektroskopii optycznej z wyładowaniem jarzeniowym (GD-OES) i skaningowej mikroskopii elektronowej (SEM) na przekroju warstwy utlenionej wykazała, że na podłożu nadstopu niklu Rene 80 tworzy się wielostrefowa zgorzelina złożona z tlenków TiO2 i Cr2O3 w strefie zewnętrznej oraz tlenek BCrO3 w strefie wewnętrznej. Poniżej warstwy wierzchniej zgorzeliny stwierdzono strefy wydzieleń nieciągłych tlenku Al2O3. Przedstawiona morfologia zgorzeliny jest charakterystyczna dla utleniania w obydwu atmosferach zarówno dla powietrza syntetycznego, jak również powietrza z parą wodną. Stwierdzono, że podczas utleniania w powietrzu syntetycznym (bez pary wodnej) tworzą się azotki TiN poniżej warstwy tlenku Al2O3. Azotki TiN nie wytworzyły się w warstwie utlenianej w atmosferze pary wodnej. Jest to spowodowane preferencyjną adsorpcją cząstek pary wodnej na powierzchni zgorzeliny.

2

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

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

Inżynieria Materiałowa

|

2001

|

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.

3

Rola mikrostruktury w procesie wysokotemperaturowego utleniania stopów TiAl.

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

Inżynieria Materiałowa

|

2001

|

R. XXII, nr 1

41-46

PL

W pracy przedstawiono wyniki badań mikrostruktury stopów Ti-50Al, Ti-48Al-2Cr i Ti-48Al-2Ag. Potwierdzono, że tworzenie ochronnej zgorzeliny Al2O3 na dwufazowych stopach TiAl zachodzi tym łatwiej, im większy jest stopień dyspersji faz alfa2-TiAl i gamma-TiAl. Metodami analitycznej transmisyjnej mikroskopii elektronowej wykazano, że dodatek srebra do stopów TiAl stabilizuje w nich fazę gamma-TiAl eliminując zarazem fazę alfa2-Ti3Al odpowiedzialną za tworzenie nieochronnego tlenku TiO2.

EN

The results of the microstructural studies of the alloys Ti-50Al, Ti-48Al-2Cr, Ti-48Al2Ag are presented. It was confirmed that the formation of the protective alumina scale on the two-phased TiAl alloys occurs more easier if the alpha2-Ti3Al phase is finely dispersed in the gamma-TiAl matrix. It has been shown using the analytical transmission electron microscopy that silver additions cause stabilisation of the gamma-TiAl phase and elimination from the alloy of the alpha2-Ti3Al phase, which is responsible for the formation of the non-protective TiO2-type scale.

4

Development of alumina forming coatings for titanium aluminides.

Singheiser L., Niewolak L., Shemet V., Gil A., Quadakkers W.J.

Inżynieria Materiałowa

|

2001

|

R. XXII, nr 5

829-833

EN

One important hindrance for the use of gamma-TiAl alloys at high temperatures is their relatively poor oxidation resistance and the sensitivity against environmentally induced embrittlement. The latter effect is also of major concern during elevated temperature application of Ti-based alloys. These problems can principally be avoided by the application of oxidation resistant, alumina forming coatings. In the present paper the possibility of using a Ag-containing TiAl alloy as a coating material for Ti and high-strength gamma-TiAl-alloys is being studied. First, oxidation tests in different environments were carried out, to compare the isothermal and cyclic oxidation resitance of a selected Ag containing coating alloy with that of two, new generation, high strength gamma-titanium aluminides. Subsequently, magnetron sputtering was used to apply the TiAl-Ag coating to a gamma-TiAl alloy (Ti-45Al-8Nb-0.2C) and to pure titanium. The coated materials were tested at 800 degrees centigrade in case of the gamma-TiAl substrate, and at 600 degrees centigrade in case of the Ti substrate. The results illustrate, that the coatings in all studied cases formed a protective alumina surface scale even up to the longest studied test times of 1000 hours. The interdiffusion processes between coating and base material, which eventually determine the coating life, were studied by SEM/EDX investigation after different exposure times.

5

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

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

Inżynieria Materiałowa

|

1998

|

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.

6

Protective coatings for high temperature applications.

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

Inżynieria Materiałowa

|

1998

|

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.

7

Microstructure and phase distribution of MCrAlY coatings.

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

Inżynieria Materiałowa

|

1998

|

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.