DE102014218595A1 - A method for at least partially removing a mixed oxide or oxide layer from a surface of a body comprising intermetallic aluminide and / or aluminum alloy - Google Patents

Abstract

The present invention relates to methods for at least partially removing a mixed oxide or oxide layer (20) from a surface (30) of a body (40) comprising intermetallic aluminide and / or an aluminum alloy and a composite material component. The composite material component is characterized in that a mixed oxide or oxide layer (20) has been removed from the surface (20) of the body (40) by one of the methods according to the invention. One method comprises evaporating the mixed oxide or oxide layer (20) using a pulsed laser beam (10). One method is characterized in that the laser beam (10) is pulsed at a pulse frequency of more than 50 kHz. The other method comprises applying a tin-based protective layer to the surface (30) and at least partially removing the mixed oxide or oxide layer (20) by breaking the oxide layer (20) by means of ultrasound.

Description

The present invention relates to a method for the at least partial removal of a mixed oxide or oxide layer from a surface of an intermetallic aluminide and / or a body comprising aluminum alloy for the material connection of a geometrically determined encapsulation and a composite material component.

Aluminum alloys are alloys of aluminum with other metals based on metal bonding, for example AlCu alloys. An alloy describes a metallic material consisting of at least two elements, which together have the metal-typical characteristic of the crystalline structure with metal bond. The alloying elements strongly affect the properties of the metal. Intermetallic aluminides, on the other hand, are intermetallic phases (intermetallic compounds) of aluminum with other metals. Intermetallic aluminides have lattice structures that are different from those of the constituent metals and result from a mixed bond of a metallic bond moiety and atomic bond fractions resulting in superstructures. An example of an intermetallic aluminide is iron aluminide.

Intermetallic aluminides and aluminum alloys are characterized by high mechanical and / or thermal stability with low weight. They are therefore suitable for reducing the weight of mechanically and / or thermally highly stressed components. Examples of such components are motors and engine parts.

However, AlCu alloys, for example, have weak casting properties. In addition, AlCu alloys are relatively expensive. Iron aluminides are brittle and therefore not easy to produce in the required shape.

One way to improve casting properties and reduce costs is to reinforce only the actual highly stressed component parts locally by one or more intermetallic aluminide or aluminum alloy components and to reinforce the remaining component parts using other aluminum alloys such as aluminum-silicon alloy finished. The respective component is thus produced as a composite material component with at least one intermetallic aluminide or aluminum alloy comprising body which is, for example, completely or partially encapsulated with the other aluminum alloy.

So that the body or bodies can unfold their positive properties with regard to mechanical and / or thermal stability in the composite material component as a whole in an economical manner, a material connection between a surface of the body, where it is connected to the aluminum alloy, and the other aluminum alloy is necessary.

However, the formation of a material bond between the surface of the aluminide intermetallic body of FeAl and the other aluminum alloy is by a mixed oxide layer or skin of Al ₂ O ₃ and Fe ₂ O ₃ , which on the surface of the Eisenaluminidkörpers after its production by contact with oxygen , For example, atmospheric oxygen, arises, impaired or made impossible. On aluminum alloy castings, such as AlCu ₄ Ti, for the AlSi gate, an oxide skin may still be formed during pouring by spontaneous oxidation. The oxide skin grows with the temperature rise.

One way to circumvent the formation of the oxide layer is to produce and maintain the intermetallic aluminide or aluminum alloy body under a protective gas atmosphere.

Out WO 03/033778 A1 For example, a method of forming a metallic conductive surface area on oxidized aluminum alloys is known. This method involves bombarding the surface area with a laser. The document mentions pulsed lasers with a pulse frequency of 1-5 kHz and a power intensity of 0.8-4 kW / mm ² .

The publication DE 102 18 563 A1 describes a method of valve seat fabrication using a laser plating process. In this case, a primary laser beam is irradiated to remove an oxide film from a casting material. At this time, the oxide film is removed by varying the intensity of the laser beam. Previously, a mixture can be injected.

The publication DE 199 35 164 A1 describes a method for the simultaneous cleaning and flux treatment of aluminum engine block cylinder bore surfaces for attachment of thermally sprayed coatings which comprises depositing double potassium aluminum fluoride salt on the surface.

An in DE 10 201 025 061 A1 described sand casting (casting in lost form) for the production of components made of aluminum alloys includes the generation of wave motion in the Melt that act to the surface to avoid oxide formation on the oxygen-accessible surface of the melt. In this case, at the latest when the melt enters sound waves are generated with up to the ultrasonic range reaching wave motion in the mold.

The inventors have found that an oxide film on a surface of a body comprising intermetallic aluminide and / or aluminum alloy can be vaporized using a pulsed laser beam when the laser beam is pulsed at a pulse frequency of over 50 kHz. Furthermore, it has been found by the inventors that at least partial removal of the oxide layer may be accomplished by ultrasonic breakup after application of a tin-based protective layer to the surface.

According to the invention, therefore, two methods are proposed for at least partially removing a mixed oxide or oxide layer from a surface of a body comprising intermetallic aluminide or aluminum alloy, one being the method according to claim 1 and the other being according to claim 9. Furthermore, a composite material component is proposed according to claim 10, wherein the composite material component comprises at least one, intermetallic aluminide or a body comprising aluminum alloy, which is integrally bonded on one surface with another aluminum alloy.

The composite material component is characterized in that a mixed oxide or oxide layer has been removed from the surface of the body by one of the methods according to the invention.

In this case, the one method comprises evaporating the mixed oxide or oxide layer using a pulsed laser beam. One method is characterized in that the laser beam is pulsed at a pulse frequency of more than 50 kHz. The other method comprises applying a tin-based protective layer to the surface and at least partially removing the oxide layer by breaking the mixed oxide or oxide layer by means of ultrasound.

Both methods have the advantage that they ensure reproducible results with reasonable economic effort. After execution of one of the methods, the body is suitable for material connection of a geometrically determined encapsulation.

In an advantageous embodiment of the one method, a power intensity of the laser beam is greater than or equal to 1 MW / cm ² . Particularly preferred is a power intensity greater than or equal to 2 MW / cm ² . In particular, a power intensity of 2.55 MW / cm ^{3 is} used. The pulse frequency may be in particular 80-120 kHz, preferably 100 kHz.

With these parameters, the Mischoxid- or oxide reduction is particularly effective.

In this case, a wavelength of the laser beam at 1064 nm (1064 nanometers) are. This allows the use of a commercially available Nd-YAG laser (neodymium-doped yttrium aluminum garnet laser).

A focal length of the laser beam may be 160mm +/- 16mm (160mm +/- 16mm) with a focal diameter of 50μm +/- 5μm (50μm +/- 5μm).

This optimizes power density and simultaneously machined area.

In particular, the body may comprise or consist of an iron aluminide (Fe-Al) which preferably has an aluminum content of 40 atomic% (+/- 5 atomic% Al) and / or a B2 crystal structure. After removal of the mixed oxide or oxide layer by means of the laser beam, in particular in the case of an iron aluminide, at least potassium fluoroaluminate (K ₂ AlF ₅ ) or a mixture comprising potassium fluoroaluminate is preferably applied to the surface.

It has been found that by a subsequent treatment of this laser passivated passivated composite surface with a chemical emulsion comprising at least K ₂ AlF ₅ , this passivation layer or the Fe ₂ O ₃ content of the mixed oxide skin can be reduced to such an extent that the intended diffusion processes are reproducible initiated and thus a material connection can be generated.

The mixture may further comprise potassium fluoride and / or aluminum fluoride in a mixing ratio between 1.8: 1 and 2.2: 1 to K ₂ AlF ₅ . In particular, the mixing ratio is 2: 1.

The body may be preheated prior to removal of the mixed oxide or oxide layer. This is for the diffusion processes that cause a material connection, advantageous.

After removal of the mixed oxide or oxide layer, the body comprising intermetallic aluminide or aluminum alloy can be stored in a protective gas atmosphere.

Further advantageous embodiments are described in the dependent claims and result from the following embodiments, in which the invention is explained with reference to the accompanying drawings. Show it:

1 an embodiment of a method according to the invention, and

2 an embodiment of the other method according to the invention.

The embodiments of the two methods according to the invention described below serve bodies comprising intermetallic aluminides, ie high-strength intermetallic phases of aluminum and other metals, for example iron aluminides (Fe-Al), and / or aluminum alloys, for example of the AlCu system to prepare a cohesive gate into other aluminum alloys, for example AlSi standard alloys. In fact, the intermetallic aluminides or aluminum alloys are distinguished by particularly high mechanical and / or thermal strength. However, the relatively weak casting technological properties of AlCu and high initial costs contradict the exclusive use of these alloys for the production of mechanically and / or thermally highly stressed components, such as engines or engine parts. FeAl, on the other hand, is inexpensive and high-strength but brittle at room temperatures, making it difficult to visualize complex structures with this material alone.

By cohesive pouring into other alloys, the strength of bodies comprising or consisting of at least one intermetallic aluminide and / or at least one aluminum alloy can nevertheless be exploited economically for components of complex geometry. Diffusion processes that can occur during the overcasting, if the body to be cast mixed oxide / oxide layer is free or has only a passivating oxide layer, namely allow both thermal and / or mechanical loads over the material boundary away in the casting material to conduct. This distinguishes overmoulding from other joining processes such as soldering, welding, gluing, composite pressing, sintering, electroplating or simple assembly. However, the prerequisite for the cohesive bond is the absence of a mixed oxide or oxide layer.

In particular, the intermetallic iron aluminides (Fe-Al) offer excellent conditions for optimizing aluminum-based cast components, since they have very high mechanical strength values, high-temperature resistant and heat-insulating and, depending on their composition, an approximately identical thermal expansion behavior to that of the other aluminum alloys. For example, an intermetallic iron aluminide with 40 at.% Al in its thermal expansion behavior is very similar to AlSi ₁₀ Mg.

Allow the execution of the inventive methods described below, oxide layers, for example, both of Al ₂ O ₃ - exist, and Fe ₂ O ₃ -Anteilen to reliably reduce or completely remove the need for cohesive composite in the cast diffusion processes to enable.

The embodiments of the two methods according to the invention described below thus prepare bodies comprising intermetallic aluminide and / or aluminum alloy in so far as that a reproducible production of integral material connections is possible in the case of the geometrically determined casting production.

In particular, the embodiments of the process according to the invention make it possible to remove strongly adhering mixed oxide layers (Al ₂ O ₃ / Fe ₂ O ₃ layers) from iron aluminides.

One of the two methods described by way of example is based on laser pulse treatment. This is a gentle, precise and very efficient surface treatment, whereby a uniform removal of large-scale mixed oxide / oxide layers can be achieved. Upon re-contact of the liberated from mixed oxide or oxide surface with the atmospheric oxygen, it can lead to an immediate spontaneous oxidation, which is known as passivation. However, the layer thickness of the passivation layer is much weaker compared to the original oxide layer.

However, by providing an inert inert gas atmosphere, protection against spontaneous oxidation can be brought about. The protective gas atmosphere can be produced, for example, by means of argon, in particular argon 4.6. For example, the mold is flooded with inlaid and removed from the oxide layer metallic aluminide body with the inert protective gas, so that a shielding of the atmospheric oxygen is formed. This is particularly advantageous for AlCu alloys.

In an optional further development of the one method, application of a potassium fluoroaluminate (K ₂ AlF ₅ ) can take place after the laser pulse treatment. The application can be carried out, for example, by dipping, brushing and / or spraying immediately after the laser treatment. The passivation layer is removed or reduced to such an extent that a reliable bond between FeAl insert and AlSi encapsulation can be produced. The mixture can further comprising potassium fluoride and / or aluminum fluoride in a mixing ratio between 1.8: 1 and 2.2: 1 to K ₂ AlF ₅ . In particular, the mixing ratio can be 2: 1. This is particularly advantageous for FeAl aluminides.

The embodiment of the other method comprises an ultrasonically assisted oxide removal under a tin-based protective layer. The tin-based protective layer is applied to an oxide layer to be removed. After removal of the oxide layer, the cleaned surface is shielded from the atmospheric oxygen and reliably protected against spontaneous oxidation, in particular during Umgusserzeugung. This is particularly advantageous for AlCu alloys.

The exemplary embodiment of a method for at least partially removing an oxide layer from a surface of a body comprising intermetallic aluminide and / or aluminum alloy is exemplified in FIG 1 shown. By means of a laser beam 10 becomes a mixed oxide or oxide layer 20 from a surface 30 of the body 40 away. There remains only a comparatively much thinner passivation layer 50 , which forms by spontaneous oxidation of short-term bare surface, if the mixed oxide or oxide layer 20 in an oxygen-containing atmosphere by means of the laser beam 10 Will get removed. In the embodiment, while the laser beam 10 pulsed generated with a pulse frequency of over 50 kHz. For example, an Nd: YAG laser (neodymium-doped yttrium aluminum garnet laser) can be used for this, so that the laser beam 10 has a wavelength of 1064 nm. The laser in the embodiment is focused on a focal point diameter of 55-55 microns, the focal length of the laser of the embodiment is 144-176 mm and the power intensity of about 1 MW / cm ² . In other embodiments, the power intensity is over 2 MW / cm ² . Further embodiments are based on a pulse frequency of 100 kHz. In particular, a power intensity of 2.55 MW / cm ^{2 can be used} together with a focal diameter of 5 μm and a focal length of 160 mm.

The laser treatment turns it into the surface 30 adherent mixed oxide or oxide layer 20 deliberately evaporated. The laser pulse leads to a self-limited process in which the base material is not attacked. The passivation layer forming immediately after evaporation 50 reliably protects against further spontaneous oxidation in subsequent process steps. It has been shown that the passivation layer 50 the necessary for the cohesion diffusion processes during the Umgießens not or only slightly affected.

Depending on the size of the body 40 For example, preheating it to an activation energy advantageous for the diffusion for the casting process, in particular for a FeAl aluminide body, may be advantageous. For example, preheating to 250-350 ° C may be advantageous. In an exemplary development of the exemplary embodiment of the one method, preheating is carried out before the laser treatment.

The laser treatment can be automated and is suitable for all sizes of metallic aluminide bodies or aluminum alloy bodies.

The laser treatment is suitable for preparing all types of intermetallic aluminide body or intermetallic aluminum alloy body for the reproducible cohesive connection in an encapsulation. In particular, it has proven advantageous for aluminum alloys with copper and iron aluminides. The laser treatment for Fe-Al materials of the crystallographic B2 structure with atomic ratio Fe to Al 60:40, corresponding to 40 at.% Al, is particularly advantageous.

Im in 2 the embodiment of the other method according to the invention for at least partially removing a mixed oxide or oxide layer from a surface of an aluminide intermetallic body or aluminum alloy body is the mixed oxide or oxide layer 20 on the surface 30 of the aluminide intermetallic body or aluminum alloy body 40 before removing the oxide layer 20 from the surface 30 with a tin layer 60 coated, which shields against oxygen in the surrounding atmosphere. Then be over a transducer 70 Well ultrasonic pulses 90 at least in the oxide layer 20 entered. The ultrasonic wave pulses 90 can also in the aluminide intermetallic body or aluminum alloy body 40 be registered. The oxide layer 20 is due to the ultrasonic wave pulses 90 mechanically under the tin layer 60 broken up. The fragments 80 the oxide layer 20 spread in the tin layer 60 ,

The surface 30 remains through the tin layer 60 protected from oxygen until the tin layer 60 during the casting over of the aluminide intermetallic body 40 is melted by the aluminum alloy. Between the aluminide intermetallic body or aluminum alloy body 40 and the other aluminum alloy can then take the necessary for the cohesion diffusion processes, since no or very little oxide hinders them.

Through the tin layer 60 will re-oxidation of the surface 30 of the intermetallic Aluminidkörpers or Aluminum alloy body 40 prevents and the surface 30 is reliably protected against spontaneous oxidation during the Umgießprozesses. Therefore, this method is especially suitable for AlCu alloys.

This embodiment of the other method according to the invention develops its advantages, especially with small aluminide intermetallic bodies or aluminum alloy bodies, which can be cast around without preheating.

The surfaces shown in the embodiments are shown flat, but the embodiments are not limited to even surfaces. Oxide layers can also be removed from any surface shapes with the methods of the exemplary embodiments, provided that the surface sections to be treated are accessible to the laser beam or the ultrasound.

LIST OF REFERENCE NUMBERS

10

laser beam

20

oxide

30

surface

40

intermetallic aluminide and / or aluminum alloy comprising body

50

passivation

60

tin-based protective layer

70

transducer

80

fragments

90

Ultrasonic

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 03/033778 A1 [0009]
• DE 10218563 A1 [0010]
• DE 19935164 A1 [0011]
• DE 10201025061 A1 [0012]

Claims (10)

Method for at least partially removing a mixed oxide or oxide layer ( 20 ) from a surface ( 30 ) of a body comprising intermetallic aluminide and / or aluminum alloy ( 40 ), comprising: - evaporating the mixed oxide or oxide layer ( 20 ) using a pulsed laser beam ( 10 ) characterized in that the laser beam ( 10 ) is pulsed with a pulse frequency of over 50 kHz. A method according to claim 1, characterized in that a power intensity of the laser beam ( 10 ) is equal to or greater than 1 MW / cm ² . A method according to claim 1 or 2, characterized in that a wavelength of the laser beam ( 10 ) at 1064 nm. Method according to one of the preceding claims, characterized in that a focal length of the laser beam ( 10 ) 160 mm +/- 16 mm. Method according to one of the preceding claims, characterized in that the body ( 40 ) has an iron aluminide (Fe-Al) and wherein after the removal of the mixed oxide or oxide layer ( 20 ) at least potassium fluoroaluminate (K ₂ AlF ₅ ) or a mixture comprising potassium fluoroaluminate on the surface ( 30 ) is applied. A method according to claim 5, characterized in that the mixture further comprises potassium fluoride and / or aluminum fluoride in a mixing ratio between 1.8: 1 and 2.2: 1 to K ₂ AlF ₅ comprises. Method according to one of the preceding claims, characterized in that the body ( 40 ) before the removal of the mixed oxide or oxide layer ( 20 ) is preheated. Method according to one of the preceding claims, characterized in that the body ( 40 ) after the removal of the mixed oxide or oxide layer ( 20 ) is stored in a protective gas atmosphere. Method for at least partially removing a mixed oxide or oxide layer ( 20 ) from a surface ( 30 ) of a body comprising intermetallic aluminide and / or aluminum alloy ( 40 ), comprising: - applying a tin-based protective layer ( 60 ) on the mixed oxide or oxide layer ( 20 ) and - at least partially removing the mixed oxide or oxide layer ( 20 ) by breaking up the oxide layer ( 20 ) by means of ultrasound ( 90 ). Composite material component comprising at least one intermetallic aluminide and / or aluminum alloy body ( 40 ), which is attached to a surface ( 30 ) is materially bonded to another aluminum alloy, characterized in that from the surface ( 30 ) of the body ( 40 ) a mixed oxide or oxide layer ( 20 ) was removed by one of the preceding methods.

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