Method for coating a component for the hot gas duct of a turbomachine

Abstract

The invention relates to a method for coating a component, which is provided for the hot gas duct of a turbomachine, wherein the coating material is applied onto the uncoated component surface in the form of particles in mixture with a binding agent, and the component with the particle-treated binding agent thereupon then undergoes thermal treatment in such a way that the binding agent is released and the coating material remains on the component.

Claims

1. A method for coating a component with a coating material, which component is provided for arrangement in the hot gas duct in a turbine center frame of a turbomachine, as a hot gas duct panel or as a fairing of a support strut supporting the bearing of the turbine shaft, comprising the steps of: keeping the coating material or a precursor thereof in the form of particles in mixture with a binding agent; applying a coat of the particle-treated binding agent onto a region of the component the entirety of which is not precoated; and thermally treating the component with the particle-treated binding agent on it so that the binding agent is released and the coating material remains on the component; and wherein the second region is a functional surface-area region of the surface of the component that represents a mounting boundary in regard to an assembly of the component with other components in the turbomachine, which remains uncoated, and wherein a surface-area proportion of at least 10% of a portion of the surface of the component exposed to the hot gas is coated and at least 20% of the surface exposed to the hot gas is uncoated; and wherein the particle-treated binding agent is applied prior to the step of thermally treating sequentially in at least two non-coextensive coats, which have at least one partial overlap with one another on the surface of the component providing a progressive stepped coating.

2. The method according to claim 1, wherein the particles comprise aluminum, which diffuses proportionately into the surface of the component during the thermal treatment and/or in which the coat is applied by spraying and/or by brushing, in particular locally.

3. The method according to claim 1, wherein the component is made of a nickel alloy.

4. The method according to claim 1, wherein the binding agent is provided on an organic base and undergoes pyrolysis during the thermal treatment.

5. The method according to claim 1, wherein the step of thermally treating the component is carried out at least at 800° C. and at most at 1200° C.

6. The method according to claim 1, wherein a surface-area proportion of at most 80% of a portion of the surface of the component exposed to the hot gas is coated.

7. The method according to claim 1, wherein, in relation to a flow in the hot gas duct, the component has a leading edge and a trailing edge as well as, further, two lateral surfaces that join the leading edge and the trailing edge to each other, wherein the leading edge and/or the trailing edge are each coated at least over a major part of their respective extent, but the lateral surfaces each remain uncoated at least in some regions.

8. The method according to claim 1, wherein the region of the surface on which the particle-treated binding agent is applied is masked with a mask during the application of the particle-treated binding agent.

9. The method according to claim 8, further comprising the steps of: providing a used component that was coated with the coating material; revising and re-coating the used component, wherein, also during the re-coating, a particle-treated binding agent is applied using the same mask for the re-coating.

10. The method according to claim 1, wherein the component is coated only in regions, by use of a local masking, and a region that is unmasked during the coating remains uncoated.

11. The method according to claim 10, wherein a coated component is configured and arranged for use in a hot gas duct of a turbomachine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in detail below on the basis of an exemplary embodiment, wherein the individual features in the scope of the independent claims can also be essential to the invention in other combinations, and also no distinction is further made in detail between the different claim categories.

(2) The invention is shown in the following figures:

(3) FIG. 1a shows a jet engine in a partially cut-away side view, schematic view;

(4) FIG. 1b shows a schematic detail view relating to FIG. 1a;

(5) FIG. 2 shows, in a side view, a fairing of a support strut from the turbine center frame;

(6) FIG. 3a shows a schematic section through a region of the component in accordance with FIG. 2 for illustration of an intermediate step of the coating method;

(7) FIG. 3b shows, likewise in a section, a layer produced in accordance with the coating method.

DESCRIPTION OF THE INVENTION

(8) FIG. 1a shows a turbomachine 1 in a partially cut-away side view, specifically a jet engine. FIG. 1b shows a schematic detail view for the latter; the following remarks relate to both figures. In terms of function, the turbomachine 1 is subdivided into compressor, combustion chamber, and turbine. Both the compressor and the turbine are each made up of a plurality of stages (not illustrated). Each stage is composed of a guide vane ring and a rotating blade ring. During operation, the rotating blade rings rotate around the longitudinal axis 2 of the turbomachine 1. The turbine shaft 3 is mounted in a bearing 4, which is held by support struts 5 (shown partially by dashed lines) in the rest of the turbomachine 1. In the region of the hot gas duct, each of the support struts 5 is clad for aerodynamic and thermal reasons, namely, by a component 6, which represents a cladding and is also referred to as a fairing.

(9) The method according to the invention has proven to be particularly advantageous especially for the coating of fairings or panels, because, in the case of these specific surface areas, processing by material removal is carried out after the coating process. By way of the coating in some regions by spraying and/or brushing (also referred to as so-called “touch-up” coating), it is possible during subsequent process steps to prevent any crack formation due to a local removal of the coating. In addition, it is also possible to avoid a complicated full-extent coverage for a local coating by gas-phase deposition.

(10) FIG. 2 shows such a fairing in an oblique view; not illustrated are the inner and outer shroud sections thus typically formed in one casting. With respect to the hot-gas flow 20, the fairing shows a leading edge 21 and a trailing edge 22 as well as, in addition, two respective lateral surfaces 23a,b that join the leading and trailing edges 21, 22 to each other and lie opposite to each other. The leading and trailing edges 21, 22 are each furnished with a coating 24. The coatings 24a,b cover the edges 21, 22 over the major part of their extent in each case, but, conversely, leave the lateral surfaces 23a,b partially uncoated. This has aerodynamic reasons—compare the introduction to the description for details. Such a coating only in some regions can be achieved with the method described below in an especially advantageous way.

(11) FIG. 3a shows a schematic section of the component 6 in a region that is coated. The component is provided from a nickel alloy and is coated with aluminum, which, however, is not deposited from the gas phase onto the uncoated surface 30 of the component 6. Instead, the aluminum is kept in a binding agent 32 in the form of particles 31, and this suspension, that is, the particle-treated binding agent 32, is applied onto the uncoated component surface 30. The binding agent 32 can be provided, for example, on an epoxy resin base, the particles 31 are admixed, and distributed uniformly by stirring prior to application, for example. The suspension can be sprayed on, comparably to a lacquer.

(12) In a next step, the component 6, onto which a coat 33 of the particle-treated binding agent 32 was applied, undergoes thermal treatment at a temperature of around 980° C. During this diffusion annealing, on the one hand, the binding agent 32 undergoes pyrolysis and vaporizes, and, on the other hand, the aluminum also diffuses proportionately into the surface 30 of the component 6. This is shown in FIG. 3b, in which the coating material 35, that is, the aluminum, is situated in part at the surface 30, but is also proportionately diffused inward. This results in a coating that well protects against oxidation the regions at and around the leading and trailing edges 21, 22 that are especially at risk of oxidation.

(13) Although the present invention has been described in detail on the basis of the exemplary embodiments, it is obvious to the person skilled in the art that the invention is not limited to these exemplary embodiments, but rather that modifications are possible in such a way that individual features are omitted or other types of combinations of features can be realized, without leaving the scope of protection of the appended claims. In particular, the present disclosure encompasses all combinations of the individual features shown in the different examples of embodiment, so that individual features that are described only in conjunction with one exemplary embodiment can also be used in other exemplary embodiments, or combinations of individual features that are not explicitly shown can also be employed.