EP3230492B1 - Method for cold gas dynamic spraying using a mask - Google Patents

Description

The invention relates to a method for coating a carrier component by cold gas spraying. In this method, a mask is placed on the carrier component prior to coating and a material is applied to the carrier component in the region of a mask opening of this mask, wherein the material completely fills the mask opening.

Cold gas spraying is a process known per se, in which particles intended for coating are preferably accelerated to supersonic speed by means of a convergent-divergent nozzle, so that they adhere to the surface to be coated on account of their impressed kinetic energy. In this case, the kinetic energy of the particles is used, which leads to a plastic deformation of the same, wherein the coating particles are melted on impact only on their surface. Therefore, this method is referred to as cold gas spraying in comparison to other thermal spraying methods, because it is carried out at comparatively low temperatures at which the coating particles remain substantially fixed. Preferably, for cold gas spraying, which is also referred to as kinetic spraying, a cold gas spraying system is used which has a gas heater for heating a gas. To the gas heater a stagnation chamber is connected, which is connected on the output side with the convergent-divergent nozzle, preferably a Laval nozzle. Convergent-divergent nozzles have a converging section and a flared section connected by a nozzle throat. The convergent-divergent nozzle produces on the output side a powder jet in the form of a gas stream with particles therein at high speed, preferably supersonic speed.

A method of the type described above is known from the prior art. According to the DE 10 2004 058 806 A1 For example, it is provided that at least one structured, electrically insulating layer and a structured, electrically conductive layer can be formed on a heat sink. For this purpose, masks are used whose openings are designed according to the structuring. The structured layers serve as circuit structures which have to satisfy electrical requirements such as a specific conductor cross-section for this purpose. The layers can be superimposed in several layer planes.

Out D.-Y. Kim et al., "Cold Spray Deposition of Copper Electrodes on Silicon and Glass Substrates," Journal of Thermal Spray Technology, Vol. 22, October 2013 It is known that the production of printed conductors by means of cold gas spraying with the aid of masks resting on the substrate, however, poses the problem that the masks necessary for this purpose have mask openings of small width. The ratio between the width of the mask openings and the mask thickness in this case leads to flow conditions of the cold gas jet in the mask opening, which complicate a deposition of the particles. Namely, a reverse flow forms on the mask walls, which leads to a triangular cross section of the deposited material, the tip of this cross section lying in the middle of the mask opening and facing the cold gas jet. No material sticks to the walls of the mask opening itself. It is important for the production of printed conductors that the cross section of the printed conductor is suitable for transmitting the required electrical current - the cross-sectional shape produced plays a minor role in comparison to this.

In order to avoid the unfavorable for the deposition of rectangular cross-sections flow conditions in the mask opening is, according to K.-R. Ernst et al., "Application variety of cold gas spraying", Proceedings of the Community Thermal Spraying eV, printing: Gerdfried Wolfertstetter, Gilching 2012 proposed that you do not have to hang up the mask for the cold gas spraying on the support member, but can fix them at a certain distance from the support member. However, this measure has the effect that, as the mask distance from the carrier component increases, the flanks of the sprayed surfaces continue to run out. The cross section of the structures produced in the mask openings is therefore also not rectangular, but approximately trapezoidal.

According to the EP 860 516 A2 a method is described in which a support member is coated by cold gas spraying. Before coating, a mask is placed on the carrier component and in the region of a mask opening of this mask a material is applied to the carrier component by cold gas spraying. The material completely fills the mask opening, which mask can be removed after making the layer.

According to the US 2007/154641 It is described that a mask can be used in a method for cold gas spraying. The mask is shaped and the process parameters of the cold gas spraying chosen so that a deposition in the shadow area of the mask is possible. As a result, undercuts can be filled with material.

According to the US 2010/230086 A1 It is described that a method for cold gas spraying can be used with a mask having a certain distance from the substrate. A part of the material is applied to the mask, whereby an application to the substrate outside the mask opening is prevented or at least reduced.

The object of the invention is to improve a method for cold gas spraying in such a way that a coating result can be produced in which the geometry of the flanks can be manufactured with comparatively high accuracy.

This object is achieved by the method described above according to the invention that in a process step after the application of the material (which is thus located in the mask opening and possibly also deposited on the edges of the mask opening), a removing process is performed, wherein the applied material, which is located above the level of the (the cold gas jet facing) top of the mask is removed. In a further method step, according to the invention, a further mask is applied to the upper side of the mask and a material applied to the already applied material in the region of a mask opening of this mask (this material can have the same composition as the previously applied material or differ in its composition ). By removing the material in the preceding method step, the further mask can be placed on the surface of the preceding mask which has been leveled thereby. Also in the area of the mask opening, a flat surface is created which lies exactly in the plane of the surface of the already filled mask. Therefore, the additional overlaid mask can be completely filled with the material again.

The two last-mentioned method steps can be carried out until the material applied has reached the required (that is, structurally predetermined) thickness on the carrier component. Thus, the coating is completed and the masks can be removed, leaving the coating result on the support member. The main advantage in the use of multiple masks is that regardless of the thickness of the coating result, the thickness of the masks can only be designed according to aspects of a flow dynamic favorable filling by the material. In other words, multiple masks are superimposed to produce the required thickness of the coating result. Each of the masks is filled individually, whereby the complete filling is ensured by the choice of the mask thickness. By the subsequent removal of the excess material is further ensured that the adjacent masks are sufficiently close to each other, so that an undisturbed formation of the corresponding portion of the coating structure can arise. As a result of the complete filling of the respective masks, flanks of the produced layer layers, which lie directly against the walls of the mask openings, advantageously arise. This also advantageous structures by cold gas spraying to produce their lateral boundaries run exactly perpendicular to the surface of the support member. In particular, columnar structures can thus also be produced if the mask openings of the adjacent masks are in each case completely superimposed on one another.

In general, the mask openings of adjacent masks must overlap, at least in some areas, so that the coating result is formed in one piece. Of course, several such coating results can be generated on the carrier component, which do not touch each other. If the successive masks have congruent mask openings or decreasing, completely superimposed mask openings, there is the additional advantage that the masks after completion of the coating can be easily removed from the component. These can then simply be lifted upwards (ie perpendicularly away from the carrier component), since no undercuts have formed in the produced coating results.

According to an advantageous embodiment of the invention, it is provided that the coating result formed on the material is separated from the carrier component. The coating result thus advantageously represents itself a component which, after the separation from the carrier component, can be supplied to its use. The carrier component itself is therefore to be understood only as a construction platform for the coating result.

Advantageously, the method according to the invention can therefore be used as a generative manufacturing method for components. In order to prepare such a method, according to an embodiment of the invention, provision may be made for the shape of the mask openings, taking into account the mask thickness for a component, to be determined by mathematically dividing the geometry of this component into superimposed disks. The calculation methods customary for this purpose are generally known and are preferably based on CAD models of the components to be manufactured. The calculated slices of the component result in the said embodiment of the method according to the invention exactly the volume of the mask openings. When determining the thickness of the discs, it is therefore necessary to take into account the thickness of the masks.

Alternatively, the method according to the invention can of course also be used to provide a component with a structured layer. This component, which can be used, for example, in a machine, in this variant of the method according to the invention represents the carrier component. The coating result in this case is the structured layer to be produced on the carrier component.

According to a particular embodiment of the invention, it is provided that at least a part of the masks has a thickness of at most 1 mm. Masks with a thickness of 1 mm have proven to be a good compromise in order to be able to produce even finer structures with the required accuracy. However, it is not absolutely necessary that all masks have a thickness of at most 1 mm. Portions of the coating result, which have larger cross-sectional areas as seen in the direction of propagation of the cold gas jet, can also be produced with larger mask openings. In this case, larger mask thicknesses can be realized, so that overall process steps can be saved in the method according to the invention. This advantageously increases the efficiency in the application of the method.

According to an advantageous embodiment when using thicker masks can be provided that at least one of the masks is filled in several steps. In this case, after the respective steps of applying the material, a removing process is carried out in which the applied material, which is located above the level of the top of the mask, is removed. This may be unevenness in the layering results that form, which already protrude beyond the plane of the upper side of the mask. In addition, these may be deposits of particles of the material which have formed on the mask edges on the top of the mask. These can gain a negative influence on the formation of the coating result as the growth progresses, which is why it may be advantageous to remove them again and again during filling of the mask.

The said deposits are also formed when using thin masks with mask openings of small width. Due to the small thickness of the mask, however, its growth during the filling of the mask openings affects comparatively small depth is not enough. It is therefore sufficient to remove these deposits after completely filling the mask opening with the material so that the subsequent mask can be placed on a flat surface that can be formed by the machined surface of the mask and the deposited material.

According to a further embodiment of the invention, it is provided that all masks whose mask openings have widths of at most 1 mm in at least one direction have a thickness of at most 1 mm. Alternatively, it can also be provided that a ratio between the thickness of the mask and the smallest width of the mask opening of at most 1 is maintained for all masks. These are advantageous design rules for the masks, which counteract the already mentioned formation of unfavorable flow conditions in the mask opening and, associated therewith, faulty filling of the mask opening with the material. The quality specifications of the coating result must be taken into account. Specifically, the formation of pores in the layer result to be formed must not exceed a value to be determined so that the layer result meets the quality requirements of the individual case.

In order to be able to check the suitability of a selected mask thickness in an application, it can advantageously be provided that the permissible thickness of at least one of the masks is determined by completely filling the mask with the material to be processed. The coating result formed from the applied material is then examined as to whether a required quality is achieved. Here, the required quality must be described by measurable parameters. As an example, the density of the coating result can be used. This gives information about the proportion of pores in the coating result. The pore size itself can also be investigated, since in particular in the wall region of the mask openings pores can accumulate and / or occur with a larger volume. This can For example, be checked by making cuts.

For the tests, either samples or the coating result to be generated itself can be produced. If the quality requirements for the coating result are met, the examination can be repeated with a mask of greater thickness. The test can thus contain several iteration steps. Alternatively, however, the method can also be used to confirm the suitability of a selected mask thickness, without exhausting any latitude in the direction of larger mask thicknesses by further iteration steps.

It is advantageous if the determined suitable thicknesses of the masks are stored together with the process parameters of the coating in a database. As a result, in subsequent methods, the determination of the mask thickness is simplified, since empirical knowledge can be used. This contains information on the geometry of the mask openings and the mask thicknesses as well as the processed materials and coating parameters set on the cold gas spraying system, such as powder delivery rate, powder type and gas temperature, gas pressure and type of carrier gas used.

A particular embodiment of the invention is obtained if at least one mask is designed in several parts, with parting lines extending from the outer edge of the mask to the mask openings. These are arranged so that the mask parts can be pulled apart parallel to their surface. This has the advantage that the mask parts can be better separated from the coating result. In particular, if the coating result has undercuts, it is not possible, as stated above, to lift the masks upwards from the carrier component. However, if there is enough room on the sides of the coating result, the mask parts can, so to speak, at least at low undercuts be pulled aside and thereby solve the coating result.

The removal of the masks up or in parts to the side has the great advantage that they can be reused for a subsequent procedure. In addition, the removal of the masks in a short time is possible, so that advantageous production time is saved. However, if a removal of the masks in whole or in parts is not possible, it is also possible to destroy them. If these are made, for example, from a less noble material than the coating result, they can be dissolved chemically or electrochemically.

Figur 1 bis 7

ausgewählte Verfahrensschritte eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens zur Erzeugung einer säulenartigen Struktur schematisch geschnitten,

Figur 8 bis 15

ausgewählte Verfahrensschritte eines anderen Ausführungsbeispiels des erfindungsgemäßen Verfahrens zur Erzeugung eines Bauteils mit Hinterschneidungen schematisch geschnitten,

Figur 16

die Aufsicht auf eine Maske mit Trennfuge und

Figur 17

ein Ausführungsbeispiel eines möglichen Bauteils in dreidimensionaler Ansicht.

Further details of the invention are described below with reference to the drawing. Identical or corresponding drawing elements are each provided with the same reference numerals and will only be explained several times as far as there are differences between the individual figures. Show it

Figure 1 to 7

schematically selected process steps of an embodiment of the inventive method for producing a columnar structure,

FIGS. 8 to 15

selected method steps of another embodiment of the inventive method for producing a component with undercuts schematically cut,

FIG. 16

the top view of a mask with parting line and

FIG. 17

an embodiment of a possible component in three-dimensional view.

The process steps of the process according to the invention can generally be represented as follows. The preparation of the method consists of the production of the masks, wherein the mask thickness of the individual masks is predetermined.

The process begins with the application of the first mask to the carrier component and filling by cold gas spraying with the material to be sprayed. Subsequently, excess material is removed from the resulting coating result and the top of the mask. Then the next mask is applied and filled again by cold gas spraying. In this case, the thickness of the mask ensures that, on the surface left free by it (the carrier component or the preceding deposit of the material), a spray layer can be deposited defect-free up to the mask edges immediately after placement. After a renewed removal of excess material can be checked whether the mask holes are completely filled. In other words, it must be determined whether the sprayed surface within the mask opening is aligned with the mask surface everywhere after ablation. This can be ensured, for example, by an automatic optical inspection method. If this is not the case, another cold gas spraying and over-milling may be performed before the next mask is applied. Only when the coating result is satisfactory, i. When all mask holes are completely filled, the next mask is placed when the structure is not finished. After completing the last mask and removing excess material, the question of completion of the coating result must be answered in the affirmative.

In FIG. 1 It can be seen how a first mask 12 has been placed on a carrier component 11. This has a mask opening 13, which in the method step according to FIG. 1 is being filled by a material 14. This is done by a non-illustrated cold gas spraying process. In FIG. 1 only a convergent-divergent spray nozzle 15 is shown, which is part of the cold gas spraying system, not shown. With the spray nozzle 15 is a Particle beam 16 directed to the support member 11, wherein both the mask opening 13 and the surface 18 of the mask 12 is provided at the edges of the mask opening 13 with layer deposits of the material 14.

In FIG. 2 It can be seen that by means of a milling head 19, the excess material according to FIG. 1 was removed. For this purpose, the milling head 19 is moved in the direction of arrow over the surface 18, wherein in FIG. 2 It can also be seen that the mask opening 13 is completely filled with the material 14.

In FIG. 3 the next two process steps are shown. Another mask 12 a is placed on the first mask 12, wherein the mask opening 13 of this mask 12 a is exactly aligned with that of mask 12. By means of the spray nozzle 15 material is again deposited until the mask opening 13 is completely filled again.

In FIG. 4 It can be seen that the excess material was removed again by means of the milling head 19 (analogous to that in FIG FIG. 2 illustrated method step).

In FIG. 5 it can be seen that analogous to FIG. 3 two further process steps were carried out, which according to a first mask 12 b was placed and this was filled by means of the spray nozzle 15, not shown here with material 14. The milling head 19 is now about to remove excess material 14 from the surface 18 of the mask 12b. The mask opening 13 of the further mask 12b is congruent with the two preceding ones.

According to FIG. 6 It can be seen that the material 14 now fills all three mask openings 13. The component is now completed, which is why the masks 12, 12a, 12b can be removed according to the arrows drawn upwards. This is easily possible because the material 14 is a columnar Structure with vertical sides (in the form of a prism) has.

Of the FIG. 7 It can be seen that the material 14 remains as a layer 20 on the support member 11. The carrier component can now be supplied to its function. A possible carrier component is for example in FIG. 17 shown. It could be a tool for embossing a symbol. The carrier component 11 in this case provides a surface on which the symbols to be embossed are constructed as a layer 20.

In the FIGS. 8 to 15 a method is shown in which the coating result results in a component 21 (cf. FIG. 15 ). The process is essentially the same as that according to the FIGS. 1 to 7 and will be explained in more detail here only in terms of its differences.

The method steps according to FIG. 8 and FIG. 9 proceed analogously to the method steps according to FIG. 1 and FIG. 2 ,

According to FIG. 10 is unlike FIG. 3 another mask 12d placed, the mask opening 13 is greater than that of the mask 12. This creates an undercut 22 in the material, which in the FIGS. 14 and 15 is better to recognize. The removal of the material according to FIG. 11 takes place analogously to FIG. 4 ,

FIG. 12 differs from FIG. 5 again, in that the further mask 12e is provided with a larger mask opening 13 than the mask 12d. Overall, the coating result of the material 14, which is in FIG. 13 can recognize, therefore, the shape of a mushroom. This makes the removal of the masks 12, 12d, 12e difficult. Have these perpendicular to the plane of a not shown parting line, so that they are made in two parts (see FIG. 16 ), the respective mask halves according to FIG 13 in the direction of the two arrows indicated parallel to the surface of the support member 11 are deducted.

However, the coating result of the material 14 may also have a geometry that does not allow lateral removal of the mask parts. In this case is in FIG. 14 shown how the masks 12, 12a, 12b can be dissolved in an electrochemical bath 25, wherein the masks in FIG. 14 are no longer recognizable because they are already resolved. In a subsequent, non-illustrated step, the resulting component 21 can be removed, for example, by wire erosion of the support member 11, which only serves as a construction platform in this process variant. The finished component 21 is in FIG. 15 shown as a side view.

FIG. 16 shows a mask 12f, which is constructed in two parts. For example, this could be for a in FIG. 13 serve indicated procedure. The mask 12f has two half masks 23, which are divisible by a parting line 24. A component which has been produced in the mask opening 13 does not interfere with removal of the mask even if overlying masks form undercuts in the component to be produced due to larger or overlapping mask openings. The prerequisite is that the undercuts are not too large (that is, the "undercuts jumps" from mask to mask), if this leads to a deposition of material on a mask showing the undercut. As a result, an adhesion of the mask to the coating result is achieved, which must be overcome by the peel force of the mask.

Claims (11)

1. Method for coating a carrier component (11) by means of cold gas dynamic spraying, in which a mask (12) is laid upon the carrier component (11) before the coating and in the region of an opening (13) of this mask (12) a material (14) is deposited on the carrier component (11), wherein the material (14) completely fills up the mask opening (13),
   characterized in that

   • in one method step, after deposition of the material (14), a removal process is carried out, in which the deposited material (14), which is located above the level of the upper side of the mask (12), is removed and a flat surface is formed in the region of the mask opening (13) and on the mask (12),

   • in a further method step an additional mask (12a, 12b, 12c, 12d) is laid upon the upper side of the mask and in the region of an opening (13) of this additional mask (12a, 12b, 12c, 12d) a material (14) is deposited upon the already deposited material (14),

   wherein the two aforesaid method steps are carried out until the deposited material (14) has achieved the required thickness on the carrier component (11) and in that after completion of the coating the masks are removed.
2. Method according to Claim 1,
   characterized in that
   the coating effect which is formed from the deposited material (14) is separated from the carrier component (11).
3. Method according to either of the preceding claims,
   characterized in that
   at least some of the masks (12, 12a, 12b, 12c, 12d) have a thickness of at most 1 mm.
4. Method according to Claim 3,
   characterized in that
   all the masks (12, 12a, 12b, 12c, 12d), the openings (13) of which have widths of at most 1 mm at least in one direction, have a thickness of at most 1 mm.
5. Method according to Claims 1 to 3,
   characterized in that
   in the case of all the masks (12, 12a, 12b, 12c, 12d), a ratio of at most 1 is maintained between thickness of the mask and smallest width of the mask opening (13).
6. Method according to one of the preceding claims,
   characterized in that
   consecutive masks (12, 12a, 12b) have congruent openings (13) or openings (13) which lie completely one on top of the other and reduce in size.
7. Method according to one of the preceding claims,
   characterized in that
   at least one mask (12f) is constructed in a multiplicity of parts, wherein parting lines (24) extend from the outer edge of the mask to the mask openings in such a way that the mask parts (23) can be pulled apart parallel to their upper side.
8. Method according to one of the preceding claims,
   characterized in that
   at least one of the masks (12, 12a, 12b, 12c, 12d) is filled up in a plurality of steps, wherein after the respective steps of depositing the material (14) a removal process is carried out, in which the deposited material (14), which is located above the level of the upper side of the mask, is removed.
9. Method according to one of the preceding claims,
   characterized in that
   the permissible thickness of at least one of the masks (12, 12a, 12b, 12c, 12d) is determined by the mask being completely filled up with the material (14) which is to be machined and by the coating effect which is formed from the deposited material (14) being subsequently tested as to whether a required quality is achieved.
10. Method according to Claim 9,
    characterized in that
    the determined, suitable thickness of the masks (12, 12a, 12b, 12c, 12d) together with the method parameters of the coating are stored in a data bank.
11. Method according to one of the preceding claims,
    characterized in that
    the design of the mask openings(13), taking into consideration the mask thickness for a component, is determined by the geometry of the component (21) being broken down by computer calculation into disks lying one on top of the other, which determine the volume of the mask openings (13).

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