WO2008080633A2

WO2008080633A2 - Method for increasing the oxidation stability of ni-base alloys by means of treatment with halogens

Info

Publication number: WO2008080633A2
Application number: PCT/EP2007/011503
Authority: WO
Inventors: Michael Schütze; Hans-Eberhard Zschau
Original assignee: Dechema Gesellschaft Für Chemische Technik Und Biotechnologie E.V.
Priority date: 2006-12-30
Filing date: 2007-12-29
Publication date: 2008-07-10
Also published as: DE112007003137A5; WO2008080633A3

Abstract

The incorporation of halogens (fluorine, chlorine, bromine, iodine) on the surface, or the regions close to the surface, of Ni-base materials can significantly increase the oxidation stability of Ni-base alloys in the temperature range from 700°C to 1300°C compared to untreated Ni-base alloys. The halogens, or halogen compounds, can be applied to the surface by means of different methods, such as by means of ion implantation, immersion, painting, spraying, or gas phase transport, or can be incorporated in the region of the components that is close to the surface.

Description

description

Process for increasing the oxidation resistance of Ni base alloys by treatment with halogens

The invention relates to a method for improving the oxidation resistance of Ni-base alloys, which form the material for a component or a component protective layer, wherein these are used in particular in a temperature range between 700 ⁰ C and 1300 ⁰ C.

According to the current state of the art, these materials are protected against oxidation by a metallic protective layer with an Al content> 10 wt .-% against oxidation. In the case of unprotected Ni-base alloys, metastable oxide phases, such as, for example, are formed after short oxidation times and at temperatures <HOO ⁰ C. B. 0-Al ₂ O ₃ , and NiO, Cr ₂ O ₅ , TiO ₂ and Ta ₂ O ₅ . Also, mixed oxides / spinel phases such. For example, NiAl ₂ O ₄ or NiCr ₂ O _{4 is} observed because there is insufficient aluminum in the Ni base alloy to form a dense protective layer of α-Al ₂ O ₃ . Rather, an internal oxidation of Al often occurs. However, the discontinuous Al ₂ O ₃ layer formed does not provide sufficient oxidation protection.

The invention is based on the object to improve the oxidation resistance of Ni-base alloys, which form the material for a component or a component protective layer, when using the components at temperatures above about 700 ⁰ C.

To solve the problem, the invention proposes

that the Ni-based alloy has a weight fraction of 1 to 10 wt .-% aluminum, and that a halogen in elemental or molecular form or a halogen compound in such an amount is applied to the surface of the component or the component protective layer or provided to the surface via the gas phase, so that a concentration of the halogen on the surface formed by the Ni-based alloy is present in excess of 2 x 10 ^"4 mol / cm ² or the concentration of the halogen in the Ni-base alloy in the near-surface region is greater than 0.1 at .-%.

The introduction of halogens (fluorine, chlorine, bromine, iodine) on the surface, which form a compound with the surface, or in the near-surface region of Ni-base materials, the oxidation resistance of Ni-base alloys in the temperature range of 700 ⁰ C to 1300 ⁰ C compared to untreated Ni-base alloys increase significantly.

The method can preferably be used with turbine blades which assume temperatures of more than 800 ^° C. during operation of the turbine.

The concentration of the halogen on the material surface is preferably not more than 1 mol / cm ² or the concentration of the halogen in the Ni-based alloy in the near-surface region is not more than 70 at.%.

In order to bring about the introduction of the halogens (fluorine, chlorine, bromine, iodine) on the surface or in the near-surface region, the component after or already in the application or providing the halogen or the halogen compound at a temperature of more than 700 ^0th C or 800 ⁰ C exposed. Preferably, the Ni-based alloy contains the elements cobalt or chromium or iron or tungsten or molybdenum or carbon or silicon or titanium or tantalum or manganese or a combination of several of the aforementioned elements as further alloying additions.

The application of the halogen or the halogen compound is carried out in solid or liquid form by a dipping method, by spreading with a brush, by a spraying method, by another known application method or by a combination of several application methods.

Another way of providing the halogen or halogen compound is to provide the halogen or halogen compound as a gas to the surface by a gas transport process.

Another way of providing the halogen or halogen compound is to introduce the halogen or halogen compound into the near-surface region by ion implantation or by a sputtering process or by a combination of both.

Preferably, the surface of the Ni-based alloy is oxidized prior to the application of the halogen or the halogen compound to form a closed alumina layer.

With the described methods of halogen treatment, the theoretically necessary minimum Al concentration for forming a continuous aluminum oxide layer is artificially reduced by accelerating aluminum from the material to the surface. basis this is the halogen effect that has already been successfully applied to components made of TiAl alloys [1-7] and in the industrial property rights [8 - 12] for TiAl alloys. The application of the halogen effect to Ni-base alloys is considered for the first time in the present application.

The effect of the invention on a component consisting of a Ni base alloy is illustrated in greater detail in FIGS. 1 and 2, the illustrations in FIG. 1 being sketches showing the photographic images of sections through the components in the Fig. 2 show schematically.

The figures each show the oxide structure of a component made of the Ni-based material IN738 after oxidation in air. The exposure of the component surface to air takes place at temperatures of 1050 ⁰ C and lasts 60 h.

FIGS. 1 a and 2 a show the component which has been implanted with fluorine according to the method according to the invention, while FIGS. 1 b and 2 b each show an untreated component.

By introducing a halogen in a suitable concentration in the near-surface zone, the formation of a thin closed layer of aluminum oxide in the near-surface region is stimulated (see Fig. Ia and 2a). The halogens or halogen compounds are first by various methods, eg. As by ion implantation, sputtering, dipping, brushing, spraying or gas phase transport, applied to the surface of the components or made available to the surface. By increasing the temperature to above 700 ^° C., the halogen or the halogen compound forms a compound with the surface or is absorbed into the surface introduced near the area of the components. The increase of the temperature can be carried out after or even during the provision of the halogens or the halogen compounds. It can also take place during the first operation of a machine equipped with the component, in which temperatures above 700 ^° C. occur.

It forms, as can be seen in Figures Ia and 2a, a closed Al ₂ O ₃ layer.

Preoxidation in an oxidizing atmosphere is recommended to form the closed protective aluminum oxide layer. Setting the halogen effect on Ni-base alloys requires a concentration of the halogen in the material volume (based on the near-surface region) of more than 0.1 at.% Or a concentration of the halogen on the material surface of more than 2 × 10 -3 mol / mol. cm ^2. Corresponding amounts of halogens or halogen compounds must therefore be provided.

Each of the above methods for introducing the halogen must therefore realize an initial concentration in the material volume close to the surface or an initial application on the surface of the material which leads to the stated values.

Figs. Ib and 2b show compared to a non-treated by the inventive process component, wherein the Al ₂ 0 ₃ layer is interrupted, thus formed is discontinuous.

Literature:

[1] M. Kumagai, K. Sibue, M. -S. Kim, M. Yonemitsu: Intermetallics 4 (1996), 557 [2] M. Hara, Y. Kitagawa: Oxidation of Metals 52 (1999), 77

[3] G. Schumacher, F. Dettenwanger, M. Schütze, U. Hornung, E. Richter, E. Wieser, W. Moeller: Intermetallics 7 (1999)

[4] A. Donchev, B. Gleeson, M. Sagittarius: Intermetallics 11 (2003), 387-398

[5] H. -E. Zschau, V. Gauthier, G. Schumacher, F. Dettenwanger, M. Schütze, H. Baumann, K. Bethge: Oxidation of Metals, 59 (2003), 183

[6] H. -E. Zschau, V. Gauthier, M. Sagittarius, H. Baumann, K. Bethge: Proc. Internat. Symposium Turbomat, Bonn, 17. - 19.6.2002, 210-214

[7] H. -E. Zschau, M. Schütze, H. Baumann, K. Bethge: Materials Science Forum 461-464 (2004), 505

[8] M. Kumagai, K. Shibue, M. -S. Kim, T. Furuyama: EP 0 580 081 A1

[9] M. Schütze, M. Haid: EP 0 770 702 A1

[10] M. Schütze, M. Haid: DE 196 27 605 Cl

[11] M. Sagittarius, G. Schumacher: DE 100 17 187 A1

[12] A. Donchev, M. Sagittarius: EP 1 462 537 A2

Claims

claims

1. A method for improving the oxidation resistance of Ni-base alloys, which form the material for a component or a component protective layer, wherein these are used in particular in a temperature range between 700 ⁰ C and 1300 ⁰ C, characterized

that the Ni-based alloy has a weight fraction of 1 to 10 wt .-% aluminum, and

that a halogen in elemental or molecular form or a halogen compound in such an amount is applied to the surface of the component or the component protective layer or provided to the surface via the gas phase, so that a concentration of the halogen on the surface formed by the Ni-based alloy is present in excess of 2 x 10 ^"4 mol / cm ² or the concentration of the halogen in the Ni-base alloy in the near-surface region is greater than 0.1 at .-%.

2. The method according to claim 1, characterized in that the concentration of the halogen on the material surface is not more than 1 mol / cm ² or the concentration of the halogen in the Ni-based alloy in the near-surface region is not more than 70 at .-%.

3. The method according to claim 1 or 2, characterized in that the component after application of the halogen or the halogen compound is exposed to a temperature of more than 800 ⁰ C.

4. The method according to claim 1, characterized in that further alloying additions to the Ni-based alloy, the elements cobalt or chromium or iron or tungsten or Molybdenum or carbon or silicon or titanium or tantalum or manganese or a combination of several of the aforementioned elements.

5. The method according to claim 1, characterized in that the halogen or the halogen compound is applied in solid or liquid form by a dipping method, by spreading with a brush, by a spray method, by another known application method or by a combination of several application methods.

6. The method according to claim 1, characterized in that the halogen or the halogen compound is provided as a gas by a gas transport process of the surface available.

7. The method according to claim 1, characterized in that the halogen or the halogen compound is introduced by ion implantation or by a sputtering process or by a combination of both in the near-surface region.

8. The method according to any one of the preceding claims, characterized in that the surface of the Ni-base alloy is oxidized prior to the application of the halogen or the halogen compound, so that forms a closed aluminum oxide layer.