METHOD FOR PRODUCING A WELDING WIRE, WELDING WIRE FOR PROCESSING A COMPONENT, AND COMPONENT

Abstract

The invention relates to a method for producing a welding wire that includes the steps of providing a hollow wire, through at least part of which at least one cavity extends; producing the welding wire by introducing a welding material containing titanium aluminide or at least one nickel-based superalloy into the at least one cavity, the at least one cavity being evacuated or being filled with a protective gas before, during and/or after the introduction of the welding material, and the hollow wire being formed from nickel if the welding material contains the at least one nickel-based superalloy. Further aspects of the invention relate to a welding wire and to a component having at least one component region obtained by hardfacing using at least one such welding wire.

Claims

1. A method for producing a welding wire, comprising the steps of: providing a hollow wire, through at least part of which at least one cavity extends; producing the welding wire by introducing a welding material containing titanium aluminide or at least one nickel-based superalloy into the at least one cavity, wherein the at least one cavity is evacuated before, during, and/or after the introduction of the welding material or is filled with a protective gas, and wherein, if the welding material contains the at least one nickel-based superalloy, the hollow wire is formed from nickel.

2. The method according to claim 1, further further comprising the step of: sealing of the cavity after the introduction of the welding material into the cavity, as a result of which any flow of fluid between the cavity and the surroundings of the welding wire is prevented.

3. The method according to claim 2, wherein the sealing of the cavity takes place by sealing at least one opening of the welding wire that connects the cavity with the surroundings at at least one welding wire end of the welding wire.

4. The method according to claim 1, wherein the hollow wire is provided by bending a sheet metal element with the creation of the cavity, wherein respective sheet metal element edges of the sheet metal element are arranged so as to adjoin each other and are subsequently joined to each other.

5. The method according to claim 4, wherein the sheet metal element edges are joined to each other by a thermal joining process, in particular a welding method.

6. The method according to claim 5, wherein the sheet metal element is placed under a vacuum atmosphere or under a protective gas atmosphere, at least during the thermal joining process.

7. The method according to claim 4, wherein the sheet metal element is shaped to form the hollow wire with the creation of a cross section of hollow cylinder shape.

8. The method according to claim 1, wherein the welding material is present in a powdered state when it is introduced into the cavity.

9. The method according to claim 1, wherein the hollow wire is formed from titanium or from aluminum if the welding material contains titanium aluminide.

10. The method according to claim 1, wherein the welding material is formed from titanium aluminide or from the at least one nickel-based superalloy.

11. The method according to claim 1, wherein the welding material contains Nb and/or Mo if the welding material contains titanium aluminide.

12. The method according to claim 1, wherein a welding wire for processing a component for a turbomachine, by hardfacing, is provided.

13. The method according to claim 1, wherein a component for a turbomachine including at least one component region, which is obtained by hardfacing using at least one welding wire, is provided.

14. The method according to claim 13, wherein at least one region of the component that differs from the component region is formed completely from titanium aluminide or completely from the at least one nick-based superalloy.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0035] Further features of the invention ensue from the claims, the figures, and the descriptions of the figures. The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the descriptions of the figures and/or shown solely in the figures can be used not only in the respectively given combinations, but also in other combinations, without leaving the scope of the invention. Accordingly, the invention is also regarded as comprising and disclosing embodiments that are not shown explicitly and explained in the figures, but can derive from and be produced from the explained embodiments by separate combinations of features. Also to be regarded as disclosed, therefore, are embodiments and combinations of features that thus do not have all features of an originally formulated independent claim.

[0036] Shown are:

[0037] FIG. 1 a cut-away illustration of a sub-region of a welding wire;

[0038] FIG. 2 a side view of the sub-region of the welding wire; and

[0039] FIG. 3 a schematic perspective view onto a component of a turbomachine, a component region of the component being formed by hardfacing using the welding wire and regions of the component that differ from the component region being formed completely from titanium aluminide.

DESCRIPTION OF THE INVENTION

[0040] FIG. 1 and FIG. 2 each show method steps for producing a welding wire 10, which, in FIG. 1 and FIG. 2, is shown only in sections in each case.

[0041] For the production of the welding wire 10, a hollow wire 12 is initially supplied, through which a cavity 14 extends. The hollow wire 12 is provided by bending a sheet metal element 26, which is formed as a titanium sheet or as a nickel sheet, that is, is formed from pure titanium or pure nickel, with creation of the cavity 14, until the sheet metal element 26 is shaped to form a hollow wire 12 with a cross section of hollow cylinder shape 32, as illustrated in FIG. 1. Each of the edges 28, 30 of the sheet metal element 26 are hereby arranged so as to adjoin each other (see FIG. 1) and are subsequently joined to each other by a thermal joining process in the form of a welding method with the creation of a weld seam 36. In summary, therefore, the hollow wire 12 is completely and thus exclusively formed from titanium or, alternatively to this, exclusively from nickel.

[0042] The sheet metal element 26 is placed under a protective gas atmosphere during the thermal joining process. To this end, the sheet metal element 26 is situated in a chamber 20, which in the present example, is filled with argon and/or helium as protective gas 18, thereby creating the protective gas atmosphere. Alternatively to this, the chamber 20 can also be evacuated, so that a vacuum atmosphere can be created in the chamber 20. The production of the welding wire 10 takes place by introducing a welding material 16, comprising a mixture of Ti, Al, Nb, and Mo or, alternatively, formed completely from titanium aluminide or, in one embodiment of the hollow wire 12, from pure nickel or, alternatively to this, from at least one nickel-based superalloy, via an opening 22, which, in the present case, is formed as a through opening, into the cavity 14, the cavity 14 being filled with the protective gas 18 before, during, and after the introduction of the welding material. During its introduction into the cavity 14, the welding material 16 is present in a powdered state. In other words, during its introduction into the cavity 14, the welding material 16 exists as a TiAl powder or as a nickel-based superalloy powder.

[0043] Both the protective gas atmosphere, which fills the cavity 14 with the protective gas 18, as well as the vacuum atmosphere have an oxygen fraction inside cavity 14, during as well as after the introduction, that can be kept at a reduced level in comparison to the surrounding air. In this way, it is possible to prevent, at least in large part, undesired oxidation processes when the welding wire 10 is later used for hardfacing.

[0044] After introduction of the welding material 16 into the cavity 14, the cavity 14 is sealed, as a result of which any flow of fluid between the cavity 14 and the surroundings of the welding wire 10 is prevented. At the latest, after the cavity is sealed, the protective gas atmosphere can be removed and thus exposure to the protective gas 18 can be ended. The cavity 14 is sealed by sealing the particular openings that connect the cavity 14 to the surroundings and lie opposite to each other at respective ends of the welding wire 10, with FIG. 2 showing, by way of example, only one of the openings, namely, an opening 22 of the welding wire 10 at one of the welding wire ends, namely, at a welding wire end 24 of the welding wire 10. In the present variant, the opening 22 at the folded welding wire end 24, for example, is sealed by a spot weld 34.

[0045] The welding wire 10 that is produced by the described method can be used for processing a component 50 of a turbomachine, for example, by means of hardfacing. The processing can involve the production or repair of the component 50.

[0046] FIG. 3 shows the component 50 for the turbomachine, which is not illustrated in more detail. In the present variant, the component 50 is designed as a blade. The component 50 comprises a component region 52 in the form of a weld seam, which is obtained by hardfacing using the welding wire 10. In the present case, each of the regions 54, 56 of the component 50, which differ from the component region 52, are formed from the titanium aluminide Ti-48Al-2Cr-2Nb. The regions 54, 56 each represent sub-segements (here, blade segments) of the component 50, which are joined to each other in a material-bonded manner via the component region 52 by hardfacing using the welding wire 10. Thus, for example, it is possible to join the region 56 to the region 54 in the course of a repair by the weld seam (component region 52). In order to avoid any crack formation due to the hardfacing, it may be appropriate to preheat the regions 54, 56 at least at a common joining zone at which the joining of the regions 54, 56 is to occur via the component region 52, to a temperature of 750-800° C., for example.

[0047] The welding wire 10, which may also be referred to as a filler wire, offers the advantage that the chemical composition of the welding material 16 (here, TiAl powder) can be chosen in such a way that the component region 52 that is formed by hardfacing can correspond to the desired value of a corresponding chemical composition of the respective regions 54, 56, which are likewise formed from TiAl. In this case, a wall thickness of the hollow wire 12 and thus a fraction of pure titanium can be taken into consideration in the component region 52 (here, the weld seam of the component 50). During hardfacing using the welding wire 10, a melt that is formed from the hollow wire 12 and the welding material 16 can likewise correspond to the composition of the respective regions 54, 56, so that the melt can accordingly have the composition Ti-48Al-2Cr-2Nb. In this way, when the regions 54, 56 are joined to the component region 52, the result is an especially homogeneous material structure that can withstand stress.

[0048] Through the use of the welding wire 10 (filler wire) during hardfacing by means of a high-energy beam (laser beam or electron beam), it is possible to prevent any absorption of moisture (entry of moisture into the cavity 14) as well as also any contaminants of the welding material 16 or of the component region 52 in an effective manner. The described method makes possible a reproducible production of the welding wire 10, as a result of which reproducible welding characteristics with, at the same time, high welding quality can be achieved. The described method makes it possible to supply especially brittle titanium aluminide (TiAl) in the cavity 14 of the welding wire 10 as a welding additive.

[0049] The welding wire 10 can also generally be used for the additive manufacture of the component 50, that is, in other words, for layer-by-layer buildup of the component 50, although, in the present case, this is not shown further. Furthermore, the production of hybrid TiAl components is possible by way of hardfacing using the welding wire 10.

[0050] The invention is based on the general knowledge that welding wires that are formed from titanium aluminide or from the at least one nickel-based superalloy cannot be produced by a conventional drawing process, especially since titanium aluminide or nickel-based superalloys are too brittle for drawing processes of this kind.

[0051] A further advantage consists in the fact that the welding wire 10 can be preheated to a very high temperature prior to the welding method (fusion welding or hardfacing), so that it is possible to dispense with a local preheating of the component 50 in order to avoid welding cracks. The welding method with a preheated welding wire 10 may also be referred to as hot-wire welding. By preheating of the welding wire 10, it is possible, for example, to reduce the power of a welding current source used for the welding method. Hot-wire welding can be carried out with an especially smaller input of heat into the component 50 and does not lead at all, or only to a small extent, to thermal distortion of the component 50.

[0052] In summary, the present method describes the production of the welding wire 10, which can be used as a filler wire in hardfacing (wire hardfacing), wherein the hollow wire 12 can form a cylindrical sheath from pure titanium or pure nickel with a predetermined wall thickness w (see FIG. 1) and wherein the welding material 16 can be formed from pure, powdered TiAl (TiAl powder) or from the at least one, pure, powdered nickel-based superalloy. The powdered TiAl or the at least one powdered nickel-based superalloy may also be referred to below simply as a powder or powder batch.

[0053] During introduction, the welding material 16 can, for example, be present as a powder batch, the chemical composition of which, under the assumption that the wall thickness w of the hollow wire 12, which is referred to below as a sheath, is formed from pure titanium or from pure nickel, and can be calculated as shown below by way of example. Respective weight proportions of the welding wire 10 can be identical to the weight proportions of the welding material 16, which is also referred to below as base material G.

[0054] Respective dimensions of the hollow wire 12 in FIG. 1 are here defined as:

d: diameter of the hollow wire 12 (see FIG. 1)
w: wall thickness of the hollow wire 12 (see FIG. 1)
l: length of a regarded wire segment of the hollow wire 12 (see FIG. 1)
Furthermore, the following applies: [0055] F.sub.P: cross-sectional area of the introduced powder [0056] F.sub.H: annular cross-sectional area of the filler wire [0057] m.sub.H: mass of the sheath with the length l [0058] M.sub.P,H: mass of the powder H made of the element of the sheath in the filler wire of length l [0059] m.sub.i: mass of the powder i made of element i of the filler wire of length l [0060] ρ.sub.H: density of the material of the sheath [0061] ρ′.sub.H: bulk density of the powder made of the element in the sheath in the filler wire [0062] ρ′.sub.i: bulk density of the powder i made of element i in the filler wire [0063] g.sub.H: nominal weight proportion of the element H in the base material G [0064] g.sub.i: nominal weight proportion of the element i in the base material G [0065] g′.sub.H: nominal weight proportion of the element H in the filler wire [0066] g′.sub.i: nominal weight proportion of the element i in the filler wire

[0067] The chemical composition of the powdered welding material 16 can be calculated under the above-mentioned assumption (sheath formed from pure titanium or pure aluminum or formed from pure nickel) with reference to FIG. 1, where the welding material 16 (base material) may also be referred to as material G:

[00001]$\begin{array}{cc}{F}_P=\frac{\pi }{4}\times {\left(d-w\right)}^2& \left(1\right)\\ F_H=\frac{\pi }{4}\times \left(2\times d-w\right)& \left(2\right)\\ m_H=F_H\times l\times {\rho }_H& \left(3\right)\\ m_{P,H}=F_P\times l\times {{\rho }^{\prime }}_H\times {g^{\prime }}_H& \left(4\right)\\ m_{P,i}=F_P\times l\times {{\rho }^{\prime }}_i\mathrm{with}i=2,3,\mathrm{.Math.}n& \left(5\right)\\ ϵ=F_H/F_P& \left(6\right)\\ g_H=\frac{{\rho }_H\times ϵ+{{\rho }^{\prime }}_H\times {g^{\prime }}_H}{{\rho }_H\times {{\mathrm{ϵ\rho }}^{\prime }}_H\times {g^{\prime }}_H+\underset{i=2}{\overset{n}{.Math.}}{{\rho }^{\prime }}_i\times {g^{\prime }}_i}& \left(7\right)\\ g_i=\frac{{\rho }_i\times {g^{\prime }}_i}{{\rho }_H\times {{\mathrm{ϵ\rho }}^{\prime }}_H\times {g^{\prime }}_H+\underset{i=2}{\overset{n}{.Math.}}{{\rho }^{\prime }}_i\times {g^{\prime }}_i}i=2,3,\mathrm{.Math.}n& \left(8\right)\end{array}$

[0068] Overall, the filler wire has the weight proportions g of the material G (welding material 16; titanium aluminide or nickel-based superalloy). This results in n linear equations (7) and (8), with which the nominal weight proportions g′ of all n elements of the welding wire 10 can be calculated in a simple manner.

[0069] The chemical composition of the welding material 16, which corresponds to a filling of the welding wire 10, can be adjusted in such a way that, after the welding method (wire hardfacing), the additively built-up component region 52 has a chemical composition that corresponds to the chemical composition of the titanium aluminide or to the chemical composition of the at least one nickel-based superalloy. In this way, it is possible to take into consideration beforehand and address any process-related vaporization of aluminum fractions during the welding method.

[0070] By use of the present method, it is possible for a filling of the hollow wire 12 with titanium aluminide or with the at least one nickel-based superalloy to take place as needed in the form of one nickel-based casting material or a plurality of nickel-based casting materials. In the latter case, the hollow wire 12 (outer sheath of the welding wire 10) is formed from pure nickel, whereas the welding material 16 (filling) is adjusted in such a way that the entire welding wire 10 corresponds to the composition of the nickel-based superalloy (or nickel-based casting alloy). If need be, it is also possible to compensate here for the vaporization of lighter alloy elements by increasing the weight proportion of these light alloy elements in the welding wire 10 beforehand, as has already been described for the process-related vaporization of the above-mentioned aluminum fractions.

[0071] The above-described nickel-based casting materials can be utilized, in particular, as blade materials in the field of a turbine of an aircraft engine and in stationary gas turbines. Typical representatives of the nickel-based casting materials are polycrystalline materials, such as, for example, INCONEL 100, INCONEL 713, or MAR-M 247 as well as monocrystalline materials, such as, for example, Rene N5, PW1484, or LEK94. These polycrystalline or monocrystalline materials are especially suitable as welding material 16 of the welding wire 10.

[0072] In order to avoid any crack formation in the region of the component region 52 that is formed by the welding method, the component 50 and, additionally or alternatively, the welding wire 10 can be heated locally to a temperature of greater than 1000° C., for example. Such a local heating of the welding wire 10 nearly to its melting temperature may also be referred to as hot-wire welding (hot-wire hardfacing). The possibility of a preheating of this kind in order to avoid crack formation represents a special advantage of the welding wire 10 in comparison to a purely powdered welding additive.

[0073] Regions that are strongly heated during the welding method and thus are hot, such as, for example, the component region 52 either can be shielded locally by the protective gas 18 or else, in an especially advantageous manner, can be placed under the protective gas 18 or under vacuum in the chamber 20.

[0074] In order to prevent any contamination of the welding material 16, the introduction of the welding material 16 can take place under the protective gas atmosphere (the atmosphere formed by the protective gas 18). In order to avoid the penetration of moisture, the welding wire ends can be sealed by the respective spot weld 34.

[0075] The welding wire 10 filled with the nickel-based superalloy as a welding material 16 is especially suitable for the repair of damaged components, such as explained on the basis of the component 50. Independently of this, the welding method using the welding wire 10 can also be employed for the production of welded constructions.

[0076] In addition to the hardfacing, the welding wire 10 can also be employed as an additive material for joint welding of welded constructions that are similar in kind or hybrid.