METAL BODIES AND METHOD FOR PRODUCTION THEREOF

Abstract

The present invention relates to methods for producing coated metal bodies by applying a metal powder composition to a metal body, such that a coated metal body is obtained, the coating of which contains one or more wax components; heating the coated metal body to the melting temperature of at least one of the wax components and subsequent cooling to room temperature, such that a coated metal body is obtained; and thermally treating the coated metal body in order to achieve alloy formation between metal portions of metal body and metal powder composition, wherein the metal body comprises nickel, cobalt, copper and/or iron and the metal powder composition comprises a metal component in powder form, which contains aluminium, silicon or magnesium in elemental or alloyed form. By melting and cooling the wax, the method makes metal bodies having a more uniform alloy coverage accessible. The invention furthermore relates to methods wherein the metal body is subsequently treated with a basic solution. The present invention additionally comprises the metal bodies obtainable by the method according to the invention, which find application as load-bearing and structural components, for example, and in catalyst converter technology.

Claims

1-12. (canceled)

13. A process for producing coated metal bodies, comprising the following steps: (a) applying a metal powder composition to a metal body so as to obtain a coated metal body 1, the coating of which contains one or more wax components; (b) heating the coated metal body 1 up to the melting temperature of at least one of the wax components and then cooling it down to room temperature so as to obtain a coated metal body 2; (c) treating the coated metal body 2 thermally in order to form an alloy between metallic components of the metal body and the metal powder composition, so as to obtain metal body 3; wherein the metal body used in step (a) comprises a metal component selected from the group consisting of: nickel, cobalt, copper, and iron; and wherein the metal powder composition used in step (a) comprises a pulverulent metal component containing aluminium, silicon or magnesium in elemental or alloyed form.

14. The process of claim 13, wherein the metal body used in step (a) is a metal foam body.

15. The process of claim 13, wherein the metal body used in step (a) consists of one of the following: metallic nickel; metallic cobalt; metallic copper; alloy of nickel and cobalt; alloy of nickel and copper; arrangements of two superposed layers of two individual metallic components, in which one of the metallic components forms an inner layer of the metal body and the other metallic component forms an outer layer of the metal body, wherein the metallic components are selected from the following combinations: nickel on the inside and cobalt on the outside; iron on the inside and nickel on the outside.

16. The process of claim 13, wherein the metal body used in step (a) consists of a metal selected from the group consisting of: Ni, Fe, Co, and Cu.

17. The process of claim 13, wherein the metal powder composition used in step (a) of the process comprises one or more pulverulent metal components selected from the group consisting of: aluminium, silicon, magnesium, alloys of aluminium and chromium, alloys of aluminium and molybdenum, alloys of aluminium and copper, alloys of aluminium and iron, alloys of aluminium and iron and chromium, alloys of aluminium and titanium, alloys of aluminium and molybdenum and titanium, alloys of silicon and chromium, alloys of silicon and molybdenum, alloys of silicon and copper, alloys of silicon and iron, alloys of silicon and iron and chromium, alloys of silicon and titanium, alloys of silicon and molybdenum and titanium, alloys of magnesium and chromium, alloys of magnesium and molybdenum, alloys of magnesium and copper, alloys of magnesium and iron, alloys of magnesium and iron and chromium, alloys of magnesium and titanium, alloys of magnesium and molybdenum and titanium.

18. The process of claim 13, wherein the metal powder composition used in step (a) consists of pulverulent aluminium and one or more pulverulent wax components.

19. The process of claim 13, wherein at least one of the wax components in the coating of the coated metal body 1 obtained in step (a) has a solidification temperature in the range from 45 to 160° C.

20. The process of claim 13, wherein one or more wax components are added to the metal powder composition used in step (a).

21. The process of claim 13, further comprising: (d) treating the metal body 3 with a basic solution.

22. The process of claim 21, wherein the treatment of metal body 3 with a basic solution is performed for a period of from 5 minutes to 8 hours at a temperature of from 20 to 120° C., and wherein the basic solution is an aqueous NaOH solution having an NaOH concentration between 2% and 30% by weight.

23. The process of claim 14, wherein the metal body used in step (a) consists of one of the following: metallic nickel; metallic cobalt; metallic copper; alloy of nickel and cobalt; alloy of nickel and copper; arrangements of two superposed layers of two individual metallic components, in which one of the metallic components forms an inner layer of the metal body and the other metallic component forms an outer layer of the metal body, wherein the metallic components are selected from the following combinations: nickel on the inside and cobalt on the outside; iron on the inside and nickel on the outside.

24. The process of claim 23, wherein the metal body used in step (a) consists of a metal selected from the following group: Ni, Fe, Co and Cu.

25. The process of claim 24, wherein the metal powder composition used in step (a) of the process comprises one or more pulverulent metal components selected from the group consisting of: aluminium, silicon, magnesium, alloys of aluminium and chromium, alloys of aluminium and molybdenum, alloys of aluminium and copper, alloys of aluminium and iron, alloys of aluminium and iron and chromium, alloys of aluminium and titanium, alloys of aluminium and molybdenum and titanium, alloys of silicon and chromium, alloys of silicon and molybdenum, alloys of silicon and copper, alloys of silicon and iron, alloys of silicon and iron and chromium, alloys of silicon and titanium, alloys of silicon and molybdenum and titanium, alloys of magnesium and chromium, alloys of magnesium and molybdenum, alloys of magnesium and copper, alloys of magnesium and iron, alloys of magnesium and iron and chromium, alloys of magnesium and titanium, alloys of magnesium and molybdenum and titanium.

26. The process of claim 25, wherein the metal powder composition used in step (a) consists of pulverulent aluminium and one or more pulverulent wax components.

27. The process of claim 26, wherein at least one of the wax components in the coating of the coated metal body 1 obtained in step (a) has a solidification temperature in the range from 45 to 160° C.

28. The process of claim 27, wherein one or more wax components are added to the metal powder composition used in step (a).

29. The process of claim 23, further comprising: (d) treating the metal body 3 with a basic solution.

30. The process of claim 29, wherein the treatment of metal body 3 with a basic solution is performed for a period of from 5 minutes to 8 hours at a temperature of from 20 to 120° C., and wherein the basic solution is an aqueous NaOH solution having an NaOH concentration between 2% and 30% by weight.

31. A coated metal body obtainable by the process of claim 13.

32. A coated metal body obtainable by the process of claim 21.

Description

EXAMPLES

[0079] A—Coating of Nickel Foam

[0080] 1. Application of Metal Powder Compositions to Metal Bodies

[0081] 40 g of binder solution (2.5% by weight of polyethyleneimine in aqueous solution) was first sprayed onto each of two metal foam bodies composed of nickel in flat form with a weight per unit area of 1000 g/m.sup.2 and an average pore size of 580 μm (1.9 mm “300 mm” 860 mm). Directly thereafter, dry pulverulent aluminium (particle size d99=90 μm) in a mixture with 3% by weight of pulverulent Ceretan®-7080 wax (melting point in the range from 140 to 160° C.) was applied to the metal bodies (about 400 g/m.sup.2).

[0082] 2. Melting and Resolidification of Wax Components

[0083] Subsequently, one of the metal foam bodies was heated to 160° C. in a laboratory oven and then cooled back down to room temperature.

[0084] 3. Thermal Treatment for Alloy Formation

[0085] Thereafter, both metal foam bodies were subjected to a thermal treatment for alloy formation under a nitrogen atmosphere in a conveyor sintering furnace (manufacturer: Sarnes). The furnace was heated from room temperature to 725° C. over the course of 15 min, and the temperature was kept at 725° C. for 2 min, followed by quenching by contacting with nitrogen atmosphere at 200° C.

[0086] 4. Determination of the Uniformity of Alloy Coverage

[0087] At the end, the scatter of the areas per unit weight of parts of the area of both metal foam bodies was determined, in order to obtain information as to the homogeneity of the alloy coverage of the two metal foam bodies. For this purpose, 36 circular cutouts each with a diameter of 30 mm were cut out of all areas of both metal foam bodies and weighed.

[0088] Subsequently, the PFR (powder foam ratio) was determined from:

PFR=100*(m[sintered]−m[original foam])/m[sintered],

[0089] with:

[0090] m[sintered]=mass of the circular cutouts each with a diameter of 30 mm that were diecut after the alloy formation

[0091] m[original foam]=mass of a circular cutout of the metal foam body with a diameter of 30 mm before the start of the experiment

[0092] At the end, averages and empirical standard deviations of the series of the respective PFR values were ascertained for both metal foam bodies.

[0093] For the metal foam body that had undergone the wax melting and resolidification step, the following result was found:

[0094] Mean: 29.7

[0095] Standard deviation: 0.5

[0096] For the metal foam body that had not undergone the wax melting and resolidification step, the following result was found:

[0097] Mean: 27.7

[0098] Standard deviation: 2.3

[0099] This result shows clearly that addition of wax and a melting-recooling step prior to the thermal treatment for alloy formation achieves a distinct increase in the uniformity of alloy coverage in the metal bodies according to the invention.

[0100] B—Coating of Wire Mesh

[0101] 1. Applying Metal Powder Compositions to Metal Bodies

[0102] Binder solution (2.5% by weight of polyethyleneimine in aqueous solution) was first sprayed onto two metal bodies composed of commercially available nickel wire mesh in two-dimensional form (mesh size 0.163 mm). Directly thereafter, an identical amount of dry pulverulent aluminium (particle size d99=90 μm) mixed with 3% by weight of pulverulent Ceretan®-7080 wax (melting point in the range from 140 to 160° C.) was applied to the two metal bodies.

[0103] 2. Melting and Resolidification of Wax Components

[0104] Subsequently, one of the metal bodies was heated to 160° C. in a laboratory oven and then cooled back down again to room temperature. The other metal body was dried at room temperature under air for 24 h.

[0105] Thereafter, the passage of light through the two metal bodies in the case of illumination from one side with a bright lamp was examined. It was found that the metal body that had undergone the melting-resolidifying operation on the wax had much more uniform passage of light than the body dried at room temperature under air. This indicates a more homogeneous distribution of the powder applied on the metal body that was actively dried at 160° C.

[0106] 3. Thermal Treatment for Alloy Formation

[0107] Thereafter, the two metal bodies were subjected to a thermal treatment for alloy formation in an industrial belt sintering furnace under a nitrogen atmosphere. The furnace here was heated up from room temperature to 725° C. over the course of 15 min, the temperature was kept at 725° C. for 2 min, followed by quenching by contacting with nitrogen atmosphere at 200° C.

[0108] C—Coating of Cobalt Foam

[0109] 1. Application of Metal Powder Compositions to Metal Bodies

[0110] 40 g of binder solution (2.5% by weight of polyethyleneimine in aqueous solution) was first sprayed onto two metal foam bodies composed of cobalt in two-dimensional form having a basis weight of 1000 g/m.sup.2, and an average pore size of 580 μm (1.9 mm “300 mm” 860 mm). Directly thereafter, dry Al/Cr powder (containing 5% by weight of Cr) (particle size d90<63 μm, d50=35 μm) mixed with 3% by weight of pulverulent Ceretan®-7080 wax (melting point in the range from 140 to 160° C.) was applied to the metal bodies (about 400 g/m.sup.2).

[0111] 2. Melting and Resolidification of Wax Components

[0112] Subsequently, one of the metal bodies was heated to 160° C. in a laboratory oven and then cooled back down again to room temperature. The other metal body was dried at room temperature under air for 24 h.

[0113] Thereafter, the passage of light through the two metal bodies in the case of illumination from one side with a bright lamp was examined. It was found that the metal body that had undergone the melting-resolidifying operation on the wax had much more uniform passage of light than the body dried at room temperature under air. This indicates a less homogeneous distribution of the powder applied in the body dried at room temperature under air. This result was confirmed by SEM, which made it possible to see the closed pores and hence local overloading of this body.

[0114] 3. Thermal Treatment for Alloy Formation

[0115] Thereafter, the two metal bodies were subjected to thermal treatment for alloy formation in a belt sintering furnace (manufacturer: Sarnes) under a nitrogen atmosphere. The furnace here was heated up from room temperature to 700° C. over the course of 15 min, the temperature was kept at 700° C. for 2 min, followed by quenching by contacting with nitrogen atmosphere at 200° C.

[0116] 4. Determination of Uniformity of Alloy Coverage

[0117] Finally, the scatter of the basis weights of parts of the area of both metal bodies was determined, in order to obtain information as to the uniformity of alloy coverage of the two metal bodies. For this purpose, 36 circular cutouts each having a diameter of 30 mm were stamped out of all areas of each of the two metal foam bodies and weighed.

[0118] Subsequently, the PFR value was determined from:

PFR=100*(m[sintered]−m[starting body])/m[sintered],

with:

[0119] m[sintered]=mass of the circular cutouts punched out after alloy formation, each having a diameter of 30 mm

[0120] m[starting body]=mass of a circular cutout of the metal body having a diameter of 30 mm before commencement of the experiment

[0121] Finally, averages and empirical standard deviations of the series of respective PFR values were ascertained for the two metal bodies.

[0122] For the metal bodies that had undergone the melting and resolidification step on the wax, the following result was found:

[0123] Average: 28.2

[0124] Standard deviation: 0.7

[0125] For the metal body that had not undergone the melting and resolidification step on the wax, the following result was found:

[0126] Average: 26.8

[0127] Standard deviation: 2.7

[0128] This result shows again that addition of wax and a melting-recooling step prior to the thermal treatment for alloy formation achieves a distinct increase in the uniformity of alloy coverage in the metal bodies according to the invention.

[0129] D—Coating of Nickel/Cobalt Foam

[0130] 1. Application of Metal Powder Compositions to Metal Bodies

[0131] 40 g of binder solution (2.5% by weight of polyethyleneimine in aqueous solution) was first sprayed onto two metal foam bodies composed of nickel/cobalt (42% by weight of nickel, 58% by weight of cobalt; produced by electroplating in layers, with template assistance) in two-dimensional form with a basis weight of 1000 g/m.sup.2, and an average pore size of 580 μm (1.9 mm “300 mm” 860 mm). Directly thereafter, dry Al/Cr powder (containing 5% by weight of Cr) (particle size d90<63 μm, d50=35 μm) mixed with 3% by weight of pulverulent Ceretan®-7080 wax (melting point in the range from 140 to 160° C.) was applied to the metal bodies (about 400 g/m.sup.2).

[0132] 2. Melting and Resolidification of Wax Components

[0133] Subsequently, one of the metal bodies was heated to 160° C. in a laboratory oven and then cooled back down again to room temperature. The other metal body was dried at room temperature under air for 24 h.

[0134] Thereafter, the passage of light through the two metal bodies in the case of illumination from one side with a bright lamp was examined. It was found that the metal body that had undergone the melting-resolidifying operation on the wax had much more uniform passage of light than the body dried at room temperature under air. This indicates a less homogeneous distribution of the powder applied in the body dried at room temperature under air. This result was confirmed by SEM, which made it possible to see the closed pores and hence local overloading of this body.

[0135] 3. Thermal Treatment for Alloy Formation

[0136] Thereafter, the two metal bodies were subjected to thermal treatment for alloy formation in a belt sintering furnace (manufacturer: Sarnes) under a nitrogen atmosphere. The furnace here was heated up from room temperature to 700° C. over the course of 15 min, the temperature was kept at 700° C. for 2 min, followed by quenching by contacting with nitrogen atmosphere at 200° C.

[0137] 4. Determination of Uniformity of Alloy Coverage

[0138] Finally, the scatter of the basis weights of parts of the area of both metal bodies was determined, in order to obtain information as to the uniformity of alloy coverage of the two metal bodies. For this purpose, 36 circular cutouts each having a diameter of 30 mm were stamped out of all areas of each of the two metal foam bodies and weighed.

[0139] Subsequently, the PFR value was determined from:

PFR=100*(m[sintered]−m[starting body])/m[sintered],

with:

[0140] m[sintered]=mass of the circular cutouts punched out after alloy formation, each having a diameter of 30 mm

[0141] m[starting body]=mass of a circular cutout of the metal body having a diameter of 30 mm before commencement of the experiment

[0142] Finally, averages and empirical standard deviations of the series of respective PFR values were ascertained for the two metal bodies.

[0143] For the metal bodies that had undergone the melting and resolidification step on the wax, the following result was found:

[0144] Average: 28.4

[0145] Standard deviation: 0.6

[0146] For the metal body that had not undergone the melting and resolidification step on the wax, the following result was found:

[0147] Average: 27.1

[0148] Standard deviation: 2.4

[0149] This result shows again that addition of wax and a melting-recooling step prior to the thermal treatment for alloy formation achieves a distinct increase in the uniformity of alloy coverage in the metal bodies according to the invention.

[0150] E—Folding Test with Nickel Foam

[0151] 1. Application of Metal Powder Compositions to Metal Bodies

[0152] 40 g of binder solution (2.5% by weight of polyethyleneimine in aqueous solution) was first sprayed onto a metal foam body composed of nickel in two-dimensional form having a basis weight of 1000 g/m.sup.2, and an average pore size of 580 μm (1.9 mm “300 mm” 860 mm). Directly thereafter, dry pulverulent aluminium (particle size d99=90 μm) mixed with 3% by weight of pulverulent Ceretan®-7080 wax (melting point in the range from 140 to 160° C.) was applied to the metal bodies (about 400 g/m.sup.2).

[0153] 2. Melting and Resolidification of Wax Components

[0154] Subsequently, the metal bodies were cut into pieces of dimensions 1.9×300×200 mm. One piece was heated to 160° C. in a laboratory oven and then cooled back down to room temperature. The other metal body was dried at room temperature under air for 24 h.

[0155] A metal body of dimensions 1.9×300×200 mm weighs about 85 g. The mass is composed of 23 g of powder, <1 g of wax and about 61 g of Ni foam.

[0156] Thereafter, the passage of light through the two metal bodies in the case of illumination from one side with a bright lamp was examined. It was found that the metal body that had undergone the melting-resolidifying operation on the wax had much more uniform passage of light than the body dried at room temperature under air. This indicates a less homogeneous distribution of the powder applied in the body dried at room temperature under air. This result was confirmed by SEM, which made it possible to see the closed pores and hence local overloading of this body.

[0157] 3. Drop Test

[0158] Thereafter, the two metal bodies were weighed and then allowed to drop onto a tabletop from a height of 10 cm. Finally, the metal bodies were weighed again.

[0159] It was found that the drop onto the tabletop resulted in a loss of about 6% of the mass of the metal powder compositions applied in the case of the metal body dried at room temperature under air for 24 h, whereas the loss of mass of the metal powder composition applied was below 1% in the case of the metal body that had undergone the melting-resolidification operation.

DESCRIPTION OF THE FIGURES

[0160] FIG. 1

[0161] The figure shows two-dimensional wire mesh blanks—on the right in the original, i.e. uncoated, form and on the left in coated form, i.e. after, as described in Example B, first an aluminium powder composition and then a cycle of melting-resolidification of wax components was run. However, the aluminium powder composition was not subsequently incorporated into the alloy by thermal treatment.

[0162] FIG. 2

[0163] The figure shows the passage of light, in the case of illumination with a bright lamp from one side, through a two-dimensional blank of cobalt foam, like that used in Example C, to which, as described in Example C, a metal powder composition has first been applied and then dried at room temperature under air for 24 hours. However, the metal powder composition was not subsequently incorporated into the alloy by thermal treatment. It is apparent that the distribution of the passage of light is less uniform than in FIG. 3. Opaque regions show closed pores and hence local overloading with metal powder composition and hence indicate inhomogeneous distribution of the metal powder composition applied.

[0164] FIG. 3

[0165] The figure shows the passage of light, in the case of illumination with a bright lamp from one side, through a two-dimensional blank of cobalt foam to which, as described in Example C, a metal powder composition has first been applied, followed by running of a cycle of melting-resolidification of wax components. However, the metal powder composition was not subsequently incorporated into the alloy by thermal treatment. It is apparent that the distribution of the passage of light is much more uniform than in FIG. 2. This indicates a more homogeneous distribution of the metal powder composition applied.

[0166] FIG. 4

[0167] The figure shows scanning electron microscope (SEM) images of samples of nickel/cobalt foam, in coated form, i.e. after, as described in Example D, a metal powder composition has been applied, but which has not subsequently been incorporated into the alloy by thermal treatment. The sample shown on the left, after application of the metal powder composition, was dried at room temperature under air for 24 hours and then examined by means of SEM. The sample shown on the right, after application of the metal powder composition, was subjected to a cycle of melting-resolidification of wax components and was then examined by means of SEM. In the sample shown on the left, the closed pores and the partly uncoated metal lands are clearly apparent. In the sample shown on the right, no closed pores and homogeneous coating of the metal lands are apparent.

[0168] FIG. 5

[0169] The figure shows, on the left-hand side, a two-dimensional blank of nickel foam to which, as described in Example E, an aluminium powder composition has first been applied and then dried at room temperature under air for 24 hours. The metal powder composition was not subsequently incorporated into the alloy by thermal treatment. The figure shows, on the right-hand side, the powder residue that remained after the powder-coated foam body had been laid down and picked up again.