BRAZE ALLOY MIX FOR APPLICATION IN A METHOD FOR BRAZING A COMPONENT, ADDITIVE ALLOY, BRAZING METHOD, AND COMPONENT

Abstract

The invention relates to a braze alloy mix for application in a method for brazing a component that has a nickel-based superalloy as base material, wherein the braze alloy mix comprises the following powders in a predetermined mixing ratio: a powder of a first braze alloy, a powder of a second braze alloy, a powder of a third braze alloy, and a powder of an additive alloy.

Claims

1. A braze alloy mix for application in a method for brazing a component that has a nickel-based superalloy as base material, wherein the braze alloy mix comprises the following powder in a predetermined mixing ratio: a powder of a first braze alloy, a powder of a second braze alloy, a powder of a third braze alloy, and a powder of an additive alloy, wherein an alloy composition of the first braze alloy comprises the following in mass percent: between 5.00% and 15.00% cobalt; between 8.00% and 16.00% chromium; between 1.00% and 4.50% aluminum; between 0.00% and 4.50% tantalum; between 0.00% and 10.0% germanium; between 1.00% and 3.00% boron; between 0.00% and 4.00% hafnium; and nickel as well as unavoidable impurities as the remainder; an alloy composition of the second braze alloy comprises the following in mass percent: between 15.00% and 25.00% chromium; between 8.50% and 13.00% titanium; between 0.00% and 5.00% niobium; and cobalt as well as unavoidable impurities as the remainder; an alloy composition of the third braze alloy comprises the following in mass percent: between 0.00% and 10.00% cobalt; between 18.00% and 30.00% chromium; between 10.00% and 14.50% titanium; between 0.00% and 1.80% niobium; and nickel as well as unavoidable impurities as the remainder; an alloy composition of the additive alloy comprises the following in mass percent: between 0.00% and 10.00% cobalt; between 10.00% and 18.00% chromium; between 4.00% and 7.00% aluminum; between 4.00% and 7.00% tantalum; between 0.00% and 3.00% molybdenum; between 5.00% and 14.00% tungsten; between 0.00% and 0.60% yttrium; between 0.00% and 2.00% hafnium; and nickel as well as unavoidable impurities as the remainder.

2. The braze alloy mix according to claim 1, wherein the alloy composition of the first braze alloy comprises the following in mass percent: between 0.00% and 0.05% yttrium.

3. The braze alloy mix according to claim 1, wherein the alloy composition of the second braze alloy (BFM2) comprises the following in mass percent: between 0.00% and 3.00% aluminum.

4. The braze alloy mix according to claim 1, wherein the alloy composition of the second braze alloy comprises the following in mass percent: between 0.00% and 7.00% tungsten.

5. The braze alloy mix according to claim 1, wherein the alloy composition of the third braze alloy (BFM3) comprises the following in mass percent: between 0.00% and 3.00% aluminum.

6. The braze alloy mix according to claim 1, wherein the alloy composition of the third braze alloy comprises the following in mass percent: between 0.00% and 5.70% tungsten.

7. The braze alloy mix according to claim 1, wherein the predetermined mixing ratio of the powders of the braze alloy mix comprises the following in mass percent: 15% first braze alloy; 25% second braze alloy; 25% third braze alloy; and 35% additive alloy.

8. The braze alloy mix according to claim 1 wherein the predetermined mixing ratio of the powders of the braze alloy mix comprises the following in mass percent: 25% first braze alloy; 12.5% second braze alloy; 12.5% third braze alloy; and 50% additive alloy.

9. The braze alloy mix according to claim 1, wherein the predetermined mixing ratio of the powders of the braze alloy mix comprises the following in mass percent: 50% first braze alloy; 10% second braze alloy; 10% third braze alloy; and 30% additive alloy.

10. The braze alloy mix according to claim 1, wherein the predetermined mixing ratio of the powders of the braze alloy mix comprises the following in mass percent: 30% first braze alloy; 10% second braze alloy; 20% third braze alloy; and 40% additive alloy.

11. The braze alloy mix according to claim 1, wherein the predetermined mixing ratio of the powders of the braze alloy mix comprises the following in mass percent: 30% first braze alloy; 20% second braze alloy; 10% third braze alloy; and 40% additive alloy.

12. The braze alloy mix according to claim 1, wherein the predetermined mixing ratio of the powders of the braze alloy mix comprises the following in mass percent: 50% first braze alloy; 10% second braze alloy; 10% third braze alloy; and 30% additive alloy.

13. An additive alloy for a braze alloy mix, wherein an alloy composition of the additive alloy comprises the following in mass percent: between 0.00% and 10.00% cobalt; between 10.00% and 18.00% chromium; between 4.00% and 7.00% aluminum; between 4.00% and 7.00% tantalum; between 0.00% and 3.00% molybdenum; between 5.00% and 14.00% tungsten; between 0.00% and 0.60% yttrium; between 0.00% and 2.00% hafnium; and nickel as well as unavoidable impurities as the remainder.

14. A method for brazing a component that has a nickel-based superalloy as base material, by a braze alloy mix according to claim 1, comprising at least the following steps: applying the braze alloy mix onto a place to be brazed of the base material of the component, heating the braze alloy mix up to a brazing temperature, wherein the brazing temperature lies between 1150 C. and 1250 C., maintaining the brazing temperature over a predetermined brazing time between 10 minutes and 24 hours, reducing the temperature to a post-treatment temperature, which lies between 1150 C. and 1180 C., and maintaining the post-treatment temperature over a predetermined post-treatment time of 1 hour to 24 hours.

15. A method of claim 14, wherein the brazing temperature lies between 1150 C. and 1250 C.

16. The method of claim 14, wherein the brazing temperature is maintained over a predetermined brazing time for 30 minutes.

17. The method of claim 14, wherein the post-treatment temperature is maintained over a predetermined post-treatment time 3 hours to 11 hours.

18. A component for a turbomachine, wherein the component has a nickel-based superalloy as base material, wherein the component is brazed by a braze alloy mix according to claim 1.

19. A component for a turbomachine, wherein the component has a nickel-based superalloy as base material, wherein the component is brazed by a braze alloy mix according to a method according to claim 14.

20. A component for a turbomachine, wherein the component has a nickel-based superalloy as base material, wherein the component is brazed by a braze alloy mix by an additive alloy according to claim 13.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0060] Additional features of the invention result from the claims, the figures, and the description of the figures. The features and combinations of features named above in the description, as well as the features and combinations of features named in the description of the figures and/or in the figures shown alone below can be used not only in the combination indicated in each case, but also in other combinations, without departing from the scope of the invention. Thus, embodiments that are not explicitly shown and explained in the figures, but proceed from the explained embodiments and can be produced by separate combination of features, are also to be viewed as comprised and disclosed by the invention. Embodiments and combination of features that thus do not have all features of an originally formulated independent claim are also to be viewed as disclosed. Moreover, embodiments and combination of features that depart from the combination of features presented in references back to the claims or deviate from these are to be viewed as disclosed particularly by the embodiments presented above. Herein:

[0061] FIG. 1 shows a schematic representation of a component for a turbomachine; and

[0062] FIG. 2 shows a schematic representation of a method for brazing a component.

DESCRIPTION OF THE INVENTION

[0063] FIG. 1 shows a schematic representation of a component C for a turbomachine. The component C can have a nickel-based superalloy as a base material G. Due to material fatigue, a crack can form in the component C, and said crack can be filled by means of a brazing method. The opening O can be filled with a braze alloy mix S in the brazing method. The braze alloy mix S can be present as a powder of a first braze alloy BFM1, a powder of a second braze alloy BFM2, and a powder of a third braze alloy BFM3. The braze alloys can differ from one another in their composition and comprise melting point reducers. The braze alloys can therefore differ from one another in their melt range. The melt range of the first braze alloy BFM1 can lie within the range of 1050 C. to 1160 C. The melt range of the second braze alloy BFM2 as well as the third braze alloy BFM3 can lie within the range of 1180 C. to 1230 C. The second braze alloy BFM2 and the third braze alloy BFM3 can be present in a eutectic or near-eutectic phase, so that a liquidus temperature T and a solidus temperature T of these braze alloys can lie together at one melting point. Based on different melt ranges of braze alloys, it may be possible in this case to melt the braze alloys sequentially. An additive alloy ADD can be mixed with the braze alloy mix S. The additive alloy ADD can be provided for the purpose of taking up at least one of the melting point reducers of the braze alloys during a manufacturing method. The additive alloy ADD can have a higher melt range than the braze alloys. The melt range of the additive alloy ADD can lie within the range of 1300 C. to 1500 C. For this purpose, the additive alloy ADD can be designed as a diffusion sink. The extent of the melting point reducers diffusing into the base material G can be reduced in this way.

[0064] FIG. 2 shows a schematic representation of a method for brazing a component C. In order to prevent brittle phases and in order to be able to make possible the reproducibility of the braze alloy mix S also in repeated repairs, a novel braze concept with four newly developed braze alloys was developed. The new braze alloy mix S is hereby characterized in that it can solidify isothermally independently of the brazing gap width; an isothermal solidification of the braze alloy mix S is primarily possible due to the interaction between the braze alloys. The new braze alloy mix S comprises three different braze alloys BFM1, BFM2, BFM3, and an additive alloy ADD of a high-melting component. The braze alloys BFM1, BFM2, BFM3 are also designated as braze filler metals, BFM.

[0065] The braze alloy mix S can be applied together with a flux and/or a binder into a site of the component C that is to be brazed, for example a crack or an opening O. The braze alloy mix S can be present as powder and can comprise a powder of a first braze alloy BFM1, a powder of a second braze alloy BFM2, a powder of a third braze alloy BFM3, and a powder of an additive alloy ADD. Exemplary alloy compositions are shown in Table 1, wherein the mass percents are indicated, also known as wt. %.

TABLE-US-00001 TABLE 1 Element BFM1 BFM2 BFM3 Additive Nickel remainder remainder remainder Cobalt 5-15 remainder 0-10 0-10 Chromium 8-16 15-25 18-30 10-18 Aluminum 1-4.5 0-3 0-3 4-7 Titanium 8.5-13 10-14.5 Tantalum max. 4 4-7 Niobium 0-5 0-1.8 Molybdenum 0-3 Tungsten 0-7 0-5.7 5-14 Germanium max. 10 Boron 1-3 Yttrium 0 to 0.1 max. 0.6 Hafnium max. 4 max. 2 (Data in mass%)

[0066] Yttrium need not absolutely be contained in BFM1. Yttrium only improves the wetting properties with respect to potentially present oxides on crack flanks. Tungsten functions as a mixed crystal or solid solution hardening element and optimizes the mechanical properties of the brazing material. The brazing strategy would work also without tungsten in BFM2 or BFM3. However, tungsten is required in the additive. Aluminum improves the oxidation properties. In order to counteract a reduction of the Al concentration from BFM1 by BFM2/BFM3 (dilution after liquid-phase homogenization), small percentages can be additionally alloyed in BFM2/BFM3. The brazing strategy here would work also without aluminum in BFM2 or BFM3.

[0067] The alloys BFM1, BFM2, BFM3, ADD can be mixed in the form of powder in precisely defined mixing ratios and applied onto the site to be repaired. The braze alloy mix S can additionally be mixed with the flux and/or the binder in order to introduce it as a paste.

[0068] The braze alloy mix can comprise the powder of the first braze alloy BFM1, the powder of the second braze alloy BFM2, the powder of the third braze alloy BFM3, and the powder of the additive alloy ADD in a predetermined mixing ratio. Possible mixing ratios are disclosed, for example, in Table 2.

[0069] The additive alloy ADD can also be mixed with conventional braze alloys from the prior art. The additive alloy ADD reduces the percentage of eutectic brittle phases due to a larger uptake capacity, whereby a higher boride precipitation potential is meant, when compared to other additive alloys according to the prior art. The mechanical properties in the region of the brazing site can be improved thereby.

TABLE-US-00002 TABLE 2 BFM1 BFM2 BFM3 ADD 15 25 25 35 25 12.5 12.5 50 50 10 10 30 30 10 20 40 30 20 10 40 50 10 10 30 (Data in mass %)

[0070] The new brazing concept provides for reducing the primary and rapidly diffusing melting point reducer boron by alternative melting point reducers. At the same time, the alternative melting point reducers should not display any negative microstructural properties. Boron and titanium can form new phases with one another in an alloy, for example, -phase er TiB2, whereby the melting point is raised. A high melting point leads to poor flow properties of the braze. For this reason, the melting point reducers were divided into functional clusters and mixed in different alloys.

[0071] The first braze alloy BFM1 contains boron and has a lower melting point in comparison to the second braze alloy BFM2 and the third braze alloy BFM3. The first braze alloy BFM1 therefore has good flow properties.

[0072] The second braze alloy BFM2 and the third braze alloy BFM3 do not contain boron. The primary melting point reducers are thereby niobium and titanium. Since niobium and titanium usually act only slightly in a melting point reducing manner, the material matrix was effectively adjusted, so that titanium and niobium have strong melting point reducing properties.

[0073] The additive alloy ADD has a higher melting point than BFM1, BFM2, BFM3 and the additive alloy. The melting point is higher than the processing temperature/brazing temperature T1, so that the additive does not melt. Also, the alloy chemistry of the additive alloy ADD was effectively optimized, so that it has a high solubility for the most rapidly diffusing melting point reducer, boron.

[0074] The second braze alloy BFM2 and the third braze alloy BFM3 are braze alloys in which the matrix was optimized with respect to reducing the temperature, and depended on the melting point reducer used. Therefore, only elements are used that are also found in nickel-based superalloys. The matrix compositions differ considerably between the second braze alloy BFM2 and the third braze alloy BFM3.

[0075] After applying the braze alloy mix S, proceeding from room temperature over a warm-up time of t1 up to a brazing temperature T1 of 1150 C. to 1250 C., particularly about 1200 C., the braze alloy mix S can be heated over a predetermined heating time. It can be provided that the braze alloys differ from one another in their melt range. The melt range of the first braze alloy BFM1 for example, can lie within the range of 1050 C. to 1160 C. and thus below the melt range of the second braze alloy BFM2 and the third braze alloy BFM3 between 1180 C. and 1230 C. Based on the different melt ranges of the braze alloys, a sequential melting of the braze alloys can take place. For example, first a solidus temperature T of the first braze alloy BFM1 can be exceeded, so that the first braze alloy BFM1 first begins to melt. During a further warm-up, a liquidus temperature T of the first braze alloy BFM1 can be exceeded, so that the first braze alloy BFM1 can be completely melted. The brazing temperature T1 can lie, for example, within the melt range of the second braze alloy BFM2 as well as within the melt range of the third braze alloy BFM3. In a further warm-up, the temperature T can exceed the solidus temperature T of the second braze alloy BFM2 as well as the third braze alloy BFM3, so that the second braze alloy BFM2 and the third braze alloy BFM3 also begin to melt. If the brazing temperature T1 lies above the liquidus temperature T of the second braze alloy BFM2 as well as of the third braze alloy BFM3, these also melt completely. The brazing temperature T1 can be selected so that it lies below a solidus temperature T of the additive alloy ADD. The additive alloy ADD is thus not melted at the brazing temperature T1. The melt range of the additive alloy ADD can lie within the range of 1300 C. to 1500 C.

[0076] The brazing temperature T1 can be maintained for a predetermined brazing time range t2 from 10 minutes up to a maximum 24 hours, usually for 30 minutes. In this way, it is possible that a liquid-phase homogenization of the first braze alloy BFM1, the second braze alloy BFM2, and the third braze alloy BFM3 takes place. During the brazing time t2, in addition to the liquid-phase homogenization of the braze alloys, a controlled diffusion of boron from the melt of the braze alloys into the additive alloy ADD can occur.

[0077] Due to the sequential melting of the brazes, the interaction between the first braze alloy BFM1, the second braze alloy BFM2, as well as the third braze alloy BFM3 should be controlled. Since the second braze alloy BFM2 and the third braze alloy BFM3 have higher melting points, the brazing temperature T1 can be raised to above the liquidus temperature of the first braze alloy BFM1, which brings about good flow properties. After the melting ranges of the second braze alloy BFM2 and of the third braze alloy BFM3 have been reached, the braze alloys are mixed by liquid-phase homogenization. The melting point reducers are thereby diluted into one another. The concentration of boron in the new melt is strongly reduced in comparison to the concentration in the first braze alloy BFM1.

[0078] Due to the simultaneous increase in solubility in the additive, the boron can be withdrawn from the melt via diffusion processes. The mixtures between the first braze alloy BFM1, the second braze alloy BFM2, and the third braze alloy BFM3 are indicated in a defined mixing ratio, so that the final alloy chemistry has a -precipitation-hardened brazing material zone. The aluminum and germanium from the first braze alloy BFM1 thereby form the -phase with the titanium and niobium from the second (BFM2) and the third braze alloy (BFM3). The high cobalt concentration from the second braze alloy BFM2 reduces the -solvus temperature, in order to secondarily precipitate the -phase despite a high concentration of -forming elements, and to be able to act to increase strength.

[0079] After the brazing time t2, the temperature T of the braze alloy mix S from the brazing temperature T1 to a post-treatment temperature T2 can be reduced over a predetermined intermediate time t3. The post-treatment temperature T2 can lie, for example, between 1150 C. and 1180 C. The post-treatment temperature T2, for example, can lie below the -solvus temperature T of the base material G of the component C, whereby any microstructural damage of the base material G can be avoided.

[0080] The post-treatment temperature T2 can be maintained over a predetermined post-treatment time t4, for example, over 1 hour to 24 hours, in particular 3 to 11 hours, in order to make possible an isothermal solidification of the braze alloy mix S. The goal is that the final brazing microstructure in the isothermal solidification arises from a melt that is alloyed within the brazing process and can therefore combine competing targeted properties by using different braze alloys.

[0081] The additive was newly developed with respect to a clearly higher solubility for the most rapidly diffusing melting point reducer, boron. If the boron concentration is reduced first by homogenization with the second braze alloy BFM2 and the third braze alloy BFM3, the braze alloy mix S should be controlled by the diffusion of the melting point reducer into particles of the additive alloy ADD. Since the boron concentration in the braze alloy mix S and the boron solubility of the additive alloy ADD were increased, the braze alloy mix S can solidify isothermally without interaction with the base material G. This means, in particular, without diffusion of boron into the base material G. The additive can also be used in combination with already existing braze alloys containing boron. The optimizing property, which is to prevent brittle phases, also reduces said phases in that case, but brittle phases cannot be completely prevented, since the boron concentration is too high in known braze alloys. The term solubility in the present case means the concentration-dependent phase transition of boron at the solidus line at process-relevant temperatures. The uptake capacity for B in the additive was increased. For such increase, a new phase formation is necessary, since the solubility of boron in nickel is negligibly small.

[0082] After the post-treatment time t4, the heating of the braze alloy mix S can be terminated, so that the temperature T can decrease over a cooling time from the post-treatment temperature T2 to room temperature T.