WO2014044431A1

WO2014044431A1 - Production of a refractory metal component

Info

Publication number: WO2014044431A1
Application number: PCT/EP2013/065207
Authority: WO
Inventors: Mathias Sommerer
Original assignee: Siemens Aktiengesellschaft
Priority date: 2012-09-24
Filing date: 2013-07-18
Publication date: 2014-03-27
Also published as: DE102012217194A1

Abstract

The invention relates to a method used for the production of a refractory metal component (1), said method having the following steps: application of a powder coating (P1-Pn) comprising refractory metal powder; and selective irradiation of the powder coating (P1-Pn) to create a beam-sintered refractory metal coating (S1-Sn). A refractory metal component (1) was produced by means of this method.

Description

description

The invention relates to a method for producing a refractory metal component, the method comprising the following steps: application of a powder layer with metal powder; and selectively irradiating the powder layer to produce a jet sintered metal layer. The invention relates to a refractory metal component which has been produced by means of the method. The invention is particularly applicable to the production of X-ray anodes, walls of a fusion reactor and 3D collimators. The plasma-facing surfaces of a wall of a fusion reactor or the surface of an X-ray anode in addition to high temperatures also high mechanical, thermocyclic loads that can lead to cracking or melting of the materials. In both applications, refractory metals, in particular tungsten, are used.

Basically known as (selective) electron beam melting ("(Selective) Electron Beam Melting", (S) EBM) or electron beam sintering a method for the production of metallic components from the powder bed. Through a

Electron beam as an energy source, a metal powder is selectively melted, which compact components of almost any geometry can be made directly from the design data. For this purpose, similar to the selective laser melting (SLM), alternately applied a powder layer by means of a so-called doctor blade to the previous and exposed by means of the electron beam. In this way, the desired component is generated in layers. Also known in principle is (selective) laser melting ("Selective Laser Melting", SLM) which is a generative manufacturing process that belongs to the group of beam melting. Selective laser melting involves the processing of pending material in powder form applied in a thin layer on a base plate. The powdery material is completely remelted locally by means of laser radiation and forms a solid layer of material after solidification. Subsequently, the base plate by the amount of a

Layer thickness lowered and powder applied again. This cycle is repeated until all layers have been remelted. The finished component is cleaned of excess powder, processed as needed or used immediately. The data for the guidance of the laser beam can be generated from a 3D CAD body by means of software. Components produced by selective laser melting are characterized by large component densities (> 99%). This ensures that the mechanical properties of the generatively produced component largely correspond to those of the base material. For the production of the powder, solid material is atomized, mechanically comminuted or chemically separated in solution. The materials used for laser melting are series materials that contain no binders. Materials used include stainless steel, tool steel, aluminum and aluminum alloys, titanium and titanium alloys, cobalt chromium, nickel-base alloys, copper alloys, ceramics and plastics. EP 0 512 633 A2 discloses a method for producing an X-ray rotary anode with a refractory region made of refractory metals. The focal area is manufactured by means of powder metallurgical processes or by means of CVD or PVD processes. The focal zone region is preferably aftertreated using high-energy electrons or photons at a depth of less than 1.5 mm by means of local superficial fusion. This reduces in particular the residual porosity in the focal area. This leads to improved mechanical properties, higher X-ray yield and significantly improved service life of such rotary anodes. WO 2008/058513 A1 discloses an electrode for the electrochemical machining of a workpiece with at least one flushing channel for the flow and exit of an electrolyte at least in a working region of the electrode, the electrode being designed as a cathodically polarized tool electrode and a geometry at least in the working region may correspond to the geometry to be removed on the workpiece. In this case, the electrode has been produced at least partially in layers by means of laser sintering, laser micro-sintering or laser melting or electron beam melting. WO 2008/058513 A1 further discloses a method for producing an electrode and uses of the electrode.

WO 2009/019645 A2 discloses a method and a device for locally applying material to a surface of an anode of an X-ray source as well as a corresponding anode. Anode material such as a repair material for filling a pit in an X-ray emitting surface (115) is applied to an X-ray emitting surface of an anode.

The location where such material is to be deposited can be detected using a laser beam. The applied repair material, including particles of anode material such as tungsten, rhenium or molybdenum, is then locally sintered using a high energy laser beam. The sintered material may then be melted using a high energy electron beam. By means of such a method, a damaged surface of an anode can be locally repaired. Alternatively, structures of different anode materials or protrusions with different levels may be provided on the X-ray emitting surface to selectively influence the X-ray emission characteristics of the anode.

It is the object of the present invention to at least partially overcome the disadvantages of the prior art and, in particular, to improve one under thermal alternating loads. It is intended to provide an inert, in particular more durable, refractory metal component which is comparatively easy to produce. This object is achieved according to the features of the independent claims. Preferred embodiments are in particular the dependent claims.

The object is achieved by a method for producing a refractory metal component, wherein the method comprises the following steps: application of a powder layer with refractory metal powder; and then selectively irradiating the powder layer to produce a refractory refractory metal layer.

This method advantageously provides new possibilities for coating surfaces with refractory metals and for producing refractory metal components, wherein in addition a highly homogeneous, isotropic microstructure of the material can be achieved. This makes it possible to improve the material properties, in particular the thermocyclic strength, which in turn extends a service life. By controlling the jet, a precise coating can be produced. About the leadership of the beam so almost any, even three-dimensional, geometry can be built or coated. Consequently, a production of whole, even complex shaped refractory metal components is possible. The refractory metal components may in particular have a non-negligible height and / or area. The jet sintering process is also suitable for coating already worn surfaces over a large area, thus providing a particularly effective repair process. The application of the powder layer can be effected for example by means of doctoring. The application of the first powder layer can be done for example on a base body. In the case of metal, sintering can also be understood as meaning a (local) melting or melting effected by the energy of the beam. It is an embodiment that the steps for producing a multilayer refractory metal component are performed multiple times. The refractory metal component is therefore in particular a layer stack. In particular, at least once a powder layer may be applied to an already jet-sintered layer. This embodiment has the advantage that thick or bulky refractory metal components can also be produced as a layer stack.

It is yet another embodiment that the irradiation is carried out by means of an electron beam, that is, the method is an electron beam sintering method (EBM).

It is yet a further embodiment that the irradiation is carried out by means of a laser beam, the method is therefore a laser beam sintering process (LBM).

The EBM method and the LBM method have the advantage that production machines are available on the market for them. In particular, by these two methods, an isotropic, fine-grained microstructure of the material can be achieved, which is advantageous for a behavior of refractory metals under thermocyclic load and in particular leads to a lifetime extension. It is also an embodiment that the refractory metal powder has at least one powder of pure refractory metal and / or a pure refractory metal alloy. Under a pure powder may be understood in particular a powder having a purity of more than 99%. This is preferred because impurities such as Fe, Ni, O ₂ or C, unlike conventional sintering processes during jet sintering, can hardly be removed due to the short heat influence and the process atmosphere. A refractory metal may in particular a particular element of the group comprising tungsten, rhenium, niobium and tantalum.

It is also an embodiment that at least the powder layer additionally comprises ceramic powder. The addition of ceramic has the advantage that during sintering, the grain boundaries of the refractory metal stabilizing effect results. The ceramic powder may in particular comprise particles of an oxide or carbide ceramic. The ceramic may in particular - sondere La ₂ 0 _3, Y ₂ O _3, TiC and / or HfC include.

In particular, a proportion of the ceramic powder on the powder layer may not exceed 20% by weight, in particular not exceed 10% by weight, in particular not exceed 5% by weight.

It is also an embodiment that a median grain size, D50, of powder particles of the refractory metal powder is less than two microns.

It is still an embodiment that the method has as additional steps: applying a powder layer of ceramic powder; and selectively irradiating the powder layer to produce a jet sintered ceramic layer. Thus, the refractory metal component can also receive or have one or more ceramic layers. In principle, it is not excluded that the refractory metal component also receives or has one or more layers of conventional metal (no refractory metal). By means of the method, a layer structure, in particular with a gradient of the properties, is thus possible.

By means of jet sintering, a surface treatment (for example structuring, additional heat treatment) may additionally be carried out at the end of the coating process.

According to yet another embodiment, an X-ray anode can be produced by means of the method. Here, the Layers are applied in particular to a carrier body of a tungsten-molybdenum alloys (in particular TZM) or carbon fiber-reinforced carbon (CFC). Alternatively, in particular a wall for a fusion reactor can be produced by means of the method.

Also, by means of the method, in particular, an SD collimator can be produced.

The object is also achieved by a refractory metal component, which has been produced by the method described above. The component can be designed analogously and has the same advantages. In particular, therefore, the entire refractory metal volume of the refractory metal component can be constructed in this way.

The refractory metal component may therefore in particular be a component made up of a plurality of refractory metal layers.

It is a further development that the composition of the refractory metal layers is the same.

It is another development that the composition of at least two refractory metal layers differs, e.g. has a sequence of W / WRe layers.

It is still a further development that the layers form a gradient stack or a gradient material, e.g. by gradually varying one or more parameters (e.g., a fraction of a particular refractory metal) over multiple layers.

Also, at least one layer may be a ceramic layer, a conventional metal layer (without refractory metal) and / or even plastic. For example, the conventional metal layer may be stainless steel, tool steel, aluminum and aluminum alloys, titanium and titanium alloys, cobalt. Chrome, nickel-based alloys or copper alloys exist.

The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of exemplary embodiments, which will be described in more detail in conjunction with the drawings.

The figure shows a sectional side view of a refractory metal component, which has been produced by means of a jet sintering process. The refractory metal component is an X-ray anode 1 by way of example here.

The X-ray anode 1 has a carrier body 2, e.g. from TZM or CFC, to which a powder layer PI with refractory metal powder has been applied in the first step by means of a doctor blade. The refractory metal powder herein comprises high purity refractory metal powder (e.g., W, Rh, Ni, Ta, etc.) and / or refractory metal alloy high purity powder (e.g., WRe, WTa, etc.). In particular, a median grain size, D50, of powder particles of the refractory metal powder may be less than two microns.

In a second step, the powder of the powder layer PI at the irradiated points has been heated to such an extent by selective (full-surface or partial) irradiation of the powder layer PI with a high-energy beam B (eg an electron beam or a laser beam) that it is sintered there , The powder layer PI has therefore been selectively sintered, in particular by means of an electron beam sintering process or a laser beam sintering process. As a result, a (jet) sintered layer ("sintered layer") S1 of refractory metal has been produced from the powder layer PI.

The powder layer PI may be used to stabilize the grain boundaries of the refractory metal or its alloy during jet sintering and thus additionally have ceramic powder for suppression of grain growth. Particularly preferred is ceramic powder with particles of La ₂ 0 ₃ , Y ₂ 0 ₃ , Tic and / or HfC. Particularly preferred is a content of the ceramic powder of not more than 5% by weight.

By repeating these steps, an X-ray anode 1 composed of respective sintered layers Si can be prepared from a plurality of powder layers Pi (i = 1,..., N).

The starting powders of the powder layers Pi may be the same or different. For example, powder layers may alternate with pure tungsten powder (eg, PI, P3, Pn-3, Pn) and powder layers with pure tungsten-rhenium powder (eg P2, Pn-1) to provide an X-ray anode 1 having a W / WRe layer structure becomes. Also, a layer height of the powder layers Pi and hence the sintered layers Si may be the same or different. There may be at least one powder layer Pn-2 substantially

(If necessary, on sintering aids) only ceramic powder, so no refractory metal powder. Thus, an X-ray anode 1 with a ceramic layer Si produced therefrom by jet sintering can also be produced. Analogously, metal layers can also be produced from conventional metal.

In particular, the powder layers Pi may only be partially irradiated or sintered, ie not over the entire surface, as is the case here, for example, in the case of the two uppermost powder layers Pn-1 and Pn. The resulting sintered layers Sn-1 and Sn are patterned and three-dimensionally formed after removal of the unsintered powder. This allows finely structured, three-dimensional refractory metal components to be produced with little effort.

Although the invention has been further illustrated and described in detail by the illustrated embodiments, the invention is not limited thereto, and other riationen can be derived therefrom by a person skilled in the art without departing from the scope of the invention.

Claims

claims

Method for producing a refractory metal component (1), the method comprising the following steps:

Applying a powder layer (PI to Pn-3, Pn-l to

Pn) with refractory metal powder; and

Selective irradiation of the powder layer (PI to Pn-3, Pn-l to Pn) for producing an associated jet-sintered sintered layer (Sl to Sn-3, Sn-1 to Sn) with refractory metal.

The method according to claim 1, wherein the steps for producing a multi-layered refractory metal component (1) are performed several times.

Method according to one of the preceding claims, wherein the irradiation is carried out by means of an electron beam (B).

Method according to one of the preceding claims, wherein the irradiation is carried out by means of a laser beam (B).

A method according to any one of the preceding claims, wherein the refractory metal powder comprises at least one powder of pure refractory metal and / or a pure refractory metal alloy.

Method according to one of the preceding claims, wherein at least one powder layer (Pi) additionally comprises ceramic powder.

The method (S1-S15) according to claim 6, wherein the ceramic powder comprises La ₂ O ₃ , Y ₂ O ₃ , Tic and / or HfC.

A method according to any one of the preceding claims, wherein a median grain size, D50, of powder particles of the refractory metal powder is less than two microns. Method according to one of the preceding claims, wherein the method comprises as additional steps:

Applying a powder layer (Pn-2) made of Keramikpul ver; and

Selective irradiation of the powder layer (Pn-2) to produce a jet-sintered ceramic layer (S2).

10. The method according to any one of the preceding claims, wherein by means of the method, an X-ray anode (1) is produced.

11. The method according to any one of claims 1 to 9, wherein by means of the method, a wall for a fusion reactor is produced.

12. The method according to any one of claims 1 to 9, wherein by means of the method, a 3D collimator is produced.

13. Refractory metal component (1), which has been produced by the method according to one of the preceding claims.