EP0664349A1 - Process for coating copper-based materials - Google Patents

Abstract

The process for protective surface coating of copper material comprises: (a) applying a cover layer alloy (14) onto the copper material (10); and (b) applying the protective layer (18) in an application surface region (32) by supplying protective layer components in the form of a protective layer alloy (38) and melting with a laser beam (22). The protective layer (18) is bonded to the copper material (10) by melting of the copper material in the application surface region. Also claimed is a workpiece of copper material which is surface fused to a protective layer consisting of several adjacent coating beads.

Description

The invention relates to a method for coating the surface of copper materials with a protective layer.

From DE-A-34 15 050 it is known, for example, to first apply the desired layer for surface refinement of copper materials by, for example, thermal spraying, galvanic processes or PVD processes and then to remelt or melt with laser radiation in order to ensure firm adhesion of the Layer on the copper material and also remove the pores. With this method, however, there are great problems due to the different wettability of the coating and the copper material and the different thermal conductivity coefficients, so that only individual traces can be remelted and no continuous, flat, wear-resistant coating can be achieved.

In addition, a one-stage coating process is known in which the coating is applied directly in a single process step and melted with laser radiation. For this, high powers are required on the one hand, and on the other hand a laser deep welding effect occurs, which leads to the fact that the Copper material is melted to a relatively great depth and the melted copper becomes part of the protective layer, so that the hardness of the protective layer is insufficient.

The invention is therefore based on the object of improving a method for providing the surface of copper material with a protective layer in such a way that the protective layer has sufficient hardness on the one hand and can also be applied over large areas.

This object is achieved according to the invention in a method of the type described in the introduction in that the copper material is provided with a cover layer by applying a cover layer alloy and in that the protective layer is then applied in the area of an application surface by supplying protective layer components in the form of a protective layer alloy and melting them with laser radiation and is connected to the copper material by melting it essentially in the area of the application surface.

The advantage of the method according to the invention can be seen in the fact that by providing the copper material with the cover layer, its optical properties for the laser radiation are changed, so that on the one hand melting of the components of the protective layer is possible with the laser radiation, and on the other hand also a melting of the Copper material in the area of the application surface and thus an intimate connection between the protective layer and the copper material, in particular with a metallurgical composite to the copper material, can be produced.

A melting bath is preferably produced with the laser beam by melting the cover layer and slightly melting the copper material, into which the protective layer alloy forming the protective layer is then introduced, the protective layer alloy either being melted directly in the melting bath or being heated by the laser beam before it hits the melting bath or is melted and the protective layer is formed in the weld pool together with the components of the cover layer.

It is particularly advantageous if the cover layer is made of a material that does not impair the properties of the protective layer, since in this case an installation of the material of the cover layer in the protective layer has no negative effects on its properties.

It is even more advantageous if the cover layer is made of material which is inert to the mechanical properties of the protective layer.

The material of the cover layer can either be selected so that it is incorporated unchanged into the protective layer or so that it is melted when the protective layer is applied.

In this case, it is particularly advantageous if the cover layer has components of the protective layer, so that components of the protective layer are already present in the form of a melt due to the melting of the cover layer.

A particularly preferred embodiment provides that the cover layer and the protective layer have the same components, preferably in the same composition. In this case, the cover layer and the material supplied to form the protective layer combine without problems to form a uniform layer which now forms the protective layer.

As already mentioned, the cover layer serves to change the laser radiation absorption of the copper material in such a way that it no longer reflects the laser radiation or only reflects it to a small extent.

It is particularly advantageous if the cover layer changes the laser radiation absorption in such a way that the cover layer and the copper material are melted together in the area of the application surface. This has the great advantage that the cover layer as such is not melted separately in front of the copper material and, as a result of different wetting conditions, the cover layer contracts as a melt on the unmelted copper material.

For this purpose, it is preferably provided that the cover layer is made sufficiently thin to be melted by the laser radiation at the same time as the copper material.

The thickness of the cover layer is, for example, approximately 100 to approximately 300 μm, while the entire protective layer that forms is in the order of approximately 1 to approximately 3 mm, preferably 2 mm.

The mass of the alloy applied as a covering layer is in a ratio of approximately 1 to 3 to approximately 1 to 5 to the mass of the protective layer alloy subsequently applied. The covering layer is preferably designed such that it is a thermal spray layer and becomes a thermal spray layer in the sense of the invention, for example understood a flame spray layer or a plasma spray layer or a vacuum spray layer or a high-speed flame spray layer or a similar layer.

Such layers can be applied in a simple and inexpensive manner and thus represent an advantageous pretreatment of the copper material used according to the invention.

In the sense of the invention, the application area is understood to be the area in which the protective layer is applied. It is preferably provided that the application area is essentially the same in terms of its extent Expansion of a melt pool area formed from the melted protective layer components corresponds when the protective layer is applied.

The method according to the invention is preferably carried out in such a way that adjacent application areas overlap.

In particular, it is provided that adjacent application areas form a coating track. In this case, it is particularly provided that a width of the coating track corresponds to a dimension of the application surface transverse to its longitudinal direction.

It has already been described in connection with the solution according to the invention that the copper material is melted in the area of the application surface. It is preferably provided that the copper material is melted in the area of the application surface over a certain depth as a thin layer. It is preferably provided that the copper material is melted at least over a depth of 10 to 50 μm.

In order to achieve a particularly advantageous anchoring of the protective layer in the copper material, it is provided, for example, that the copper material is melted in a partial area of the application surface by the deep welding effect. In this case, the protective layer extends deep into the copper material in this area and is thus anchored in a form-fitting manner via a nose.

No details have so far been given regarding the type of protective layers. It is preferably provided that the protective layer is formed from alloys which comprise one or more of the components nickel, cobalt or iron.

It is preferably also provided that the cover layer is a layer which comprises one or more of the components nickel, cobalt or iron.

In order to obtain crack-free protective layers, it is particularly advantageous if the copper material is preheated to apply the protective layer, preferably to a temperature between approximately 100 ° C. and approximately 500 ° C., in particular approximately between 200 ° C. and approximately 400 ° C.

The entire workpiece is preferably heated. In addition, the invention relates to a workpiece made of a copper material provided with a protective layer, which according to the invention is characterized in that the copper material is melted on the surface in the area of overlap by the protective layer and that the protective layer is formed from a plurality of coating traces lying side by side.

It is particularly advantageous if the protective layer is positively anchored in the copper material in a partial area of its overlap of the workpiece with a nose.

Further features and advantages of the invention are the subject of the following description and the drawing of an embodiment of a method according to the invention and a protective layer according to the invention.

Fig. 1

eine schematische Darstellung eines ersten Verfahrensschritts zum Aufbringen einer Deckschicht;

Fig. 2

eine schematische Darstellung eines zweiten Verfahrensschritts zum Aufbringen der Schutzschicht;

Fig. 3

einen Querschnitt durch ein erstes Ausführungsbeispiel einer Spur einer Schutzschicht quer zur Bewegungsrichtung beim Aufbringen derselben;

Fig. 4

einen Querschnitt, in Ansicht ähnlich Fig. 3, durch mehrere, nebeneinanderliegende Spuren von Schutzschichten gemäß dem ersten Ausführungsbeispiel;

Fig. 5

eine exemplarische Darstellung der Oberflächenhärte bei der Schutzschicht gemäß Fig. 4;

Fig. 6

einen Querschnitt durch ein zweites Ausführungsbeispiel einer Spur einer Schutzschicht quer zur Bewegungsrichtung beim Aufbringen derselben ähnlich Fig. 3 und

Fig. 7

einen Querschnitt durch mehrere nebeneinanderliegende Spuren von Schutzschichten gemäß dem zweiten Ausführungsbeispiel und ähnlich Fig. 4.

The drawing shows:

Fig. 1

a schematic representation of a first method step for applying a cover layer;

Fig. 2

a schematic representation of a second process step for applying the protective layer;

Fig. 3

a cross section through a first embodiment of a trace of a protective layer transverse to the direction of movement when applying the same;

Fig. 4

a cross section, in a view similar to Figure 3, through several, adjacent tracks of protective layers according to the first embodiment.

Fig. 5

an exemplary representation of the surface hardness in the protective layer of FIG. 4;

Fig. 6

a cross section through a second embodiment of a trace of a protective layer transverse to the direction of movement when applying the same similar to Fig. 3 and

Fig. 7

3 shows a cross section through several adjacent tracks of protective layers according to the second exemplary embodiment and similar to FIG. 4.

In one exemplary embodiment of a method according to the invention, as shown in FIG. 1, in a first method step a workpiece 10 is provided on a surface 12 with a cover layer 14 applied thereon.

This is preferably done in a conventional coating system 16, in which thermal spray layers can be produced, the coating system 16 being designed as a conventional coating system for producing flame spray layers or plasma spray layers or vacuum spray layers or else high-speed spray layers.

The cover layer 14 preferably has a thickness of 100 to 500 μm.

The workpiece made of a copper material is preferably made of pure copper or copper alloys, wherein this workpiece 10 can be any type of component made of copper. For example, components of this type are molds or rollers for the steel industry, in which the high thermal conductivity of the copper is important and on the other hand the surface 12 of the workpiece 10 must be protected.

After the surface 12 of the workpiece 10 has been provided with the cover layer 14, a protective layer 18 for the surface 12 of the workpiece 10 is applied in a laser coating system 20, which has a high-power laser 24 generating laser radiation 22 and a processing head 26 with focusing optics 28, which images the laser radiation 22 coming from the high-power laser 24 onto a focal spot 30. The laser radiation 22 creates a weld pool 32 in the area of the focal spot 30, in which all components of the later protective layer 18 are melted and from which the protective layer 18 is separated by cooling, the weld pool 32 in a direction of movement 34 parallel to the surface 12 of the workpiece 10 migrates and the melt pool 32 is supplied with the individual components of the protective layer 18 essentially in the form of a powder jet 38 via a coating module designated as 36, this powder jet 38 still from an inert atmosphere, preferably a protective gas jacket made of, for example, helium and / or argon , for example supplied with a throughput of 5-50 l / min, is surrounded. For this purpose, a powder conveyor system 40 supplying the coating module 36 is additionally provided.

The protective layer 18 applied to the workpiece 10 is, for example, a nickel-based alloy, but other alloys can also be used as the protective layer, for example alloys based on cobalt or iron.

A first exemplary embodiment of such a protective layer 18 applied in the form of a so-called track 42 is shown in FIG. 3, the cover layer 14 still being recognizable on both sides of an edge of the track 42, characterized by lines 44 and 46. Furthermore, it can be seen that in the area of a width B of the track 42 not only the cover layer 14 melted and passed into the protective layer 18, but also in the area of a depth T below the surface 12 the copper material of the workpiece 10 itself was melted, and thus part of the copper has also found its way into the weld pool 32. This co-melting of the material of the workpiece 10 in the region of the depth T below the surface 12 creates a firm adhesion of the protective layer 18 on the workpiece 10, so that the protective layer 18, which is known from the prior art, no longer flakes off can.

In addition, the focal spot 30 is preferably designed such that a deep welding effect of the laser radiation 22 occurs in a narrow central area S of the track 42 and thus the material of the workpiece 10 is melted even deeper in this area S, to a depth TN , and the solidified protective layer 18 extends with a nose 48 deep into the workpiece 10 and is thus additionally positively anchored in the workpiece 10 with this nose 48.

By overlapping such individual tracks 42, as shown in FIG. 4, a surface coating of the workpiece 10 over any width is possible, each track 42 being anchored in the workpiece 10 with its own nose 48 and thus the overall protective layer that is formed 18 is also anchored several times via the lugs 48 in the workpiece 10.

The properties of a workpiece 10 provided with such a protective layer 18, for example its hardness properties, are shown by way of example in FIG. 5. It can be seen that the protective layer 18 has an essentially constant hardness parallel to the surface, while at a distance from a surface of the protective layer 18 as far as the depth of the workpiece 10, the hardness remains approximately constant, namely over the thickness D of Protective layer 18, and then on the hardness of the material of the workpiece 10 itself, ie the copper material.

Furthermore, with such a protective layer 18, apart from the nose 48, the workpiece 10 has melted to a depth T below the original surface of approximately 10 to approximately 100 μm, preferably approximately 50 to approximately 100 μm. This material of the workpiece 10 has been absorbed in the protective layer 18. This melting of the workpiece 10 at a shallow depth below the surface 12 already enables an intimate connection between the protective layer 18 and the workpiece 10.

In a second exemplary embodiment of a protective layer 18 'applied in the form of a track 42', as shown in FIG. 6, the cover layer 14 can also be seen on both sides of an edge of the track 42, characterized by lines 44 and 46, and furthermore is also shown in the area of a width B of the track 42 'not only melted the cover layer 14 and also passed into the protective layer 18', but also also melted in the area T below the surface 12 of the copper material of the workpiece 10 to form a metallurgical bond with the copper material to manufacture the workpiece 10.

In contrast to the first exemplary embodiment, however, the formation of the nose 48 by means of the deep-welding effect is absent, so that the layer 18 'only adheres firmly to the workpiece 10 with the melted-on region with the depth T and the metallurgical bond that forms and the protective layer flakes off 18 'can no longer take place.

With the protective layer 18 'according to the second exemplary embodiment, it is also possible, as shown in FIG. 7, to overlap several tracks 42' next to one another, so that these form a continuous, large-area protective layer 18 'on the workpiece 10, which is likewise only via the metallurgical composite, formed by co-melting of the copper material of the workpiece 10 adheres to the workpiece 10 in the region of the depth T (preferably approximately 50 to approximately 100 μm) without the formation of the lugs 48 being necessary.

Otherwise, the second exemplary embodiment of the protective layer 18 ′ according to the invention is designed in exactly the same way as the first exemplary embodiment, so that full reference can be made to the first exemplary embodiment with regard to further features.

The following copper materials can be used both in the first and in the second exemplary embodiment of the protective layer according to the invention.

pure copper

• containing oxygen (for electrical engineering) e.g. E-Cu 58 (DIN 1787)
• oxygen-free (for apparatus construction) e.g. SF-Cu (DIN 1787)

low-alloy copper materials

• aushärtbare Knetlegierung z.B. CuCrZr (DIN 17666)
• nicht aushärtbare Knetlegierung z.B. CuTeP (DIN 17666)
• aushärtbare Gußlegierung z.B. G-CuCr (DIN 17655)

(Concentration of alloying elements <1%, balance Cu)

• hardenable wrought alloy e.g. CuCrZr (DIN 17666)
• not hardenable wrought alloy e.g. CuTeP (DIN 17666)
• hardenable cast alloy e.g. G-CuCr (DIN 17655)

Copper-zinc alloy (DIN 17660)

• without further alloying elements (5 - 40% Zn, rest Cu)
• with lead (0.5 - 3% Pb, approx. 40% Zn, rest Cu)
• with other alloying elements (Al, Mn, Sn, Fe, Ni, Pb, As)

Copper-tin alloy (DIN 17662)

(2 - 5% Sn, up to 0.4% P, balance Cu)

Copper-nickel alloy (DIN 17664)

(9.5 - 44% Ni, Sn, Fe, Mn, balance Cu)

Copper-aluminum alloy (DIN 17665)

(5 - 11% Al, As, Fe, Mn, Ni, rest Cu)

Furthermore, a cover layer with a thickness of 100 to 500 μm, preferably approximately 300 to approximately 500 μm, is preferably applied as a thermal protective layer, for which the following alloys can be used:

Nickel based alloy

Cr 5 to 25% by weight
B 2 to 4% by weight
Si 2 to 4% by weight
W 0 to 15% by weight
C 0 to 6% by weight
Mo 0 to 5% by weight
Ti 0 to 2% by weight
Rest Ni

Iron-based alloy

Cr 5 to 25% by weight
B 2 to 4% by weight
Si 2 to 4% by weight
W 0 to 15% by weight
C 0 to 6% by weight
Mo 0 to 5% by weight
Ti 0 to 2% by weight
Rest of Fe

Cobalt-based alloy

Cr 5 to 25% by weight
B 2 to 4% by weight
Si 2 to 4% by weight
W 0 to 15% by weight
C 0 to 6% by weight
Mo 0 to 5% by weight
Ti 0 to 2% by weight
Rest co
The protective layer is applied with a thickness D of at least 100 to 300 μm, preferably approximately 1 to approximately 3 mm, preferably approximately 1 to approximately 2 mm, preferably also using the nickel-based alloy or the cobalt-based alloy or the iron-based alloy as stated above.

The protective layer is a homogeneously mixed layer in the case of applying an alloy as a cover layer and later applying the same alloy to form the protective layer, which layer also includes the alloy of the cover layer.

Claims (17)

Process for coating the surface of copper materials with a protective layer, characterized in that the copper material is provided with a cover layer by applying a cover layer alloy and that the protective layer is then applied in the area of an application surface by supplying protective layer components in the form of a protective layer alloy and melting them with laser radiation and by an essentially melting of the copper material in the area of the application surface is connected to it. A method according to claim 1, characterized in that the cover layer is made of material which does not impair the properties of the protective layer. Method according to Claim 1 or 2, characterized in that the cover layer is made of material which is inert to the mechanical properties of the protective layer. Method according to one of the preceding claims, characterized in that the material of the cover layer is also melted when the protective layer is applied. A method according to claim 4, characterized in that the cover layer is made of a material which comprises protective layer components. Method according to one of the preceding claims, characterized in that the cover layer changes the laser radiation absorption in such a way that the cover layer and the copper material are melted together in the area of the application surface. Method according to one of the preceding claims, characterized in that the cover layer is applied to the surface of the copper material in the form of a thermal spray layer. Method according to one of the preceding claims, characterized in that the application area essentially corresponds in terms of its extent to the extent of a melt pool region formed from the melted protective layer components. Method according to one of the preceding claims, characterized in that adjacent application surfaces overlap. Method according to claim 9, characterized in that adjacent application surfaces form a coating track. Method according to one of the preceding claims, characterized in that the copper material is melted in the area of the application surface over a certain depth as a thin layer. Method according to one of the preceding claims, characterized in that the copper material is melted in a partial area of the application surface by the deep welding effect. Method according to one of the preceding claims, characterized in that the protective layer is formed from an alloy which comprises one or more of the components nickel, cobalt or iron. Method according to one of the preceding claims, characterized in that the cover layer is formed from an alloy which comprises one or more of the components nickel, cobalt or iron. Method according to one of the preceding claims, characterized in that the copper material is preheated to apply the protective layer. Workpiece made of a copper material provided with a protective layer, characterized in that the copper material is melted on the surface in the area of the overlap by the protective layer and the protective layer is formed from a plurality of coating traces lying side by side. Workpiece according to claim 16, characterized in that the protective layer is anchored in a form-fitting manner in the copper material in a partial area of its overlap of the workpiece.

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