Patent Application
20080305276
This application claims the priority of International Application No. PCT/DE2005/001041, filed May 20, 2005, and German Patent Document No. 10 2004 025 139.8, filed May 21, 2004, the disclosures of which are expressly incorporated by reference herein.
The invention relates to a method of applying hot gas anticorrosion layers to a material with a Ni-based or Co-based material.
In aircraft gas turbines, hot gas corrosion protection in the high temperature range is required in the area of the high pressure turbine, in particular the blades and vane segments. To do so, the components, which are made of a Ni-based material (in special cases also a Co-based material) are coated with a noble metal from the platinum group, preferably platinum itself.
Then the respective component is diffusion-annealed at a temperature of approx. 1000° C. The resulting composite material is then aluminized by a thermochemical process. Aluminizing creates a PtAl gradient material which forms Al2O3 at the surface during operation, thus providing a protective layer against corrosive gases (e.g., nitrogen oxides, sulfur oxides). This protective layer is initially consumed by the corrosive/erosive attack. However, due to boundary diffusion of aluminum present in the material in combination with the free oxygen in the turbine gas, new Al2O3 is constantly being formed again, and thus an appropriate protective effect is maintained. When the Al present in the material is consumed due to the constant boundary diffusion, a corresponding component (blade, vane segment) must be aluminized again for reuse.
Traditional methods of producing the hot gas anticorrosion layers are galvanic or chemical methods, for example. These two method variants are characterized in that the layer is applied at least in a primary step from the liquid phase. One disadvantage of these methods is that not all combinations of materials can be produced. In addition, these methods are comparatively cost intensive due to the great amount of time/labor involved.
The object of the invention is to provide a correspondingly economical method with which hot gas anticorrosion layers may be applied to a Ni-based or Co-based material.
According to the invention, metallic precursors are introduced into a directional high-temperature, high-enthalpy jet to produce the hot gas anticorrosion layers; a metal vapor is generated from the metallic precursors and deposited on a component to form a gradient layer.
First an adhesive layer of an identical material or at least a related material is advantageously applied to the base material of the hot gas components, which are blades and vane segments, for example, and are usually made of high-temperature-resistant nickel alloys (but also Co alloys). According to the invention, this is also accomplished by a coating method characterized by a directional high-temperature, high-enthalpy flow. A plasma flow, primarily of a thermal nature (thermodynamic equilibrium plasma flow, characterized by either a full or local thermodynamic equilibrium, FTE, LTE) may advantageously be used here. Corresponding plasma flows can be produced by expanding high-current arc discharges (working range of the arc voltages preferably greater than 100 V, working range of the arc currents preferably greater than 500 Å) using argon/hydrogen primary gases.
Alternatively, high-enthalpy flows of the required power range may be produced by high frequency-induced plasmas (e.g., by inductive coupling of electromagnetic radiation in the frequency range of 0.8 MHz to 10 MHz).
In such high temperature high-enthalpy flows, a powdered material of the Ni-based or Co-based material or a similar material may be vaporized or fragmented on a nanoscale to produce an adhesive layer. This following expansion of the metal vapor bound to the carrier gas leads to a directional free jet and to deposition of a fine crystalline layer. The entire relevant component is coated.
An alternative method of applying the adhesive layer utilizing the specific properties of high-temperature, high-enthalpy flows consists of introducing gaseous precursors (e.g., sublimed halides from the corresponding salt compounds, practical examples of which include NiCl2, Al2Cl6, CoCl2, PtCl4, PdCl2) or direct precursor gases (e.g., Al(CH)3, Ni(CO)4) and liquid precursors (e.g., H2PtCl6) into the flows and reducing them to metal atoms and/or metallic nanoparticles (metal clusters) by means of proportional hydrogen in the process gas.
The result of this process variant is likewise a metal vapor bound to a carrier gas in accordance with the previous variant of metal powders.
Following this, the actual hot gas anticorrosion layer is applied in gradient form with different concentrations of the required constituents by an identical method.
A specific exemplary embodiment is illustrated in
The specific layer of
It is advantageous that the mixing ratios and/or gradients which may be implemented in virtually any form may be adapted to the specific corrosion conditions. These depend on the particular temperature of the component and the specific pressure, the amount of corrosive gases resulting from the fuel composition and the individual combustion chamber parameters (average and local flame temperatures, average and local oxygen levels).
It is also advantageous that the desired layer composition can be adjusted by means of the inventive method in a one-step process management.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 025 139.8 | May 2004 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE2005/001041 | 5/20/2005 | WO | 00 | 7/29/2008 |
