Abstract
Presented is a method for forming at least one structure on a substrate. Utilizing a low-temperature plasma jet, powder, of which the structure shall be constructed, is applied to a surface of the substrate. Using at least one laser beam, heat is input into the substrate and/or the powder within a laser incidence region on the substrate. The heat input delays solidification of the powder particles, which are partly or fully melted in the plasma jet, on the substrate and thereby enables the formation of good adhesion between the applied powder, and thus the structure constructed out of the powder, and the substrate. The invention further relates to an apparatus for performing the method.
Claims
1. A method for forming at least one structure from a powder on a surface of a substrate, the method comprising the steps of: depositing the powder on the surface of the substrate by a low-temperature plasma jet during a relative movement between the low-temperature plasma jet and the substrate wherein the low-temperature plasma jet defines a plasma incidence region on the substrate; directing at least one laser beam onto the substrate and thereby defining a laser incidence region, wherein a defined relative position between the laser incidence region of the at least one laser beam and the plasma incidence region of the low-temperature plasma jet is given; and, causing a heat input in the substrate and/or the powder by the at least one laser beam in the laser incidence region; wherein a solidification of molten material of the powder is delayed in such a way by the heat input that the molten material can spread on the surface of the substrate; and, wherein the surface of the substrate in the laser incidence region remains in a solid condition when impinged by the at least one laser beam.
2. The method of claim 1, wherein the defined relative position between the laser incidence region and the plasma incidence region is such that the laser incidence region is located outside of the plasma incidence region and has not yet been impinged with powder.
3. The method of claim 2, wherein the at least one laser beam is guided such that it does not traverse the low-temperature plasma jet.
4. The method of claim 2, wherein the at least one laser beam is guided such that it traverses the low-temperature plasma jet.
5. The method of claim 1, wherein the laser incidence region overlaps with the plasma incidence region.
6. The method of claim 5, wherein the laser incidence region is completely located within the plasma incidence region.
7. The method of claim 1, wherein a diameter of the laser incidence region is smaller than a diameter of the plasma incidence region.
8. The method of claim 1, wherein the powder which has been directed by the low-temperature plasma jet on the surface of the substrate outside of the at least one structure formed by a cooperation of the low-temperature plasma jet and the at least one laser beam is removed from the surface of the substrate.
9. The method of claim 7 wherein a diameter of the laser incidence region is smaller than 1 mm.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying figures, in which:
(2) FIG. 1 is a first embodiment of the method, where the laser beam is guided before the plasma jet;
(3) FIG. 2 shows a top view onto a surface of the substrate, which is subjected to the embodiment of the method of FIG. 1;
(4) FIG. 3 shows a second embodiment of the method, where the laser beam traverses the plasma jet;
(5) FIG. 4 shows a third embodiment of the method, where the laser beam is directed into the plasma jet;
(6) FIG. 5 shows a top view similar to FIG. 2, wherein the substrate, which is subjected to the embodiment of the method as shown in FIG. 4;
(7) FIG. 6 shows an embodiment of the device according to the invention; and,
(8) FIG. 7 shows a further embodiment of the device according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
(9) At the outset, it should be appreciated that like reference characters on different drawing views identify identical, or functionally similar, structural elements of the invention. While the present invention is described with respect to what is presently considered to be the preferred aspects, it is to be understood that the invention as claimed is not limited to the disclosed aspect. Also, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments or of being practiced or carried out in various ways and is intended to include various modifications and equivalent arrangements within the spirit and scope of the appended claims.
(10) Furthermore, it is understood that this invention is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims. The invention expressly also covers the combinations of features of the embodiments described.
(11) Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices, and materials are now described.
(12) FIG. 1 shows a first schematic embodiment of the method and the apparatus according to the invention for forming a structure 2 on a substrate 100. A powder 20 is supplied to a low-temperature plasma jet 10 and deposited on a surface 1 of the substrate 100 by the plasma jet 10. The powder 20 is fed to the plasma jet 10 by a powder feed 21, which here is shown only schematically. The plasma jet 10 exits from a processing head 11, which is connected to a plasma generator, which is not shown here. A laser beam 30, generated here by a laser 31, is directed onto the surface 1 of the substrate and there defines a laser incidence region 35 (see FIG. 2) in a region, which has not yet been impinged with powder 20 by the plasma jet 10. The arrangement of processing head 11, laser 31 and powder feed 21 is guided and moved respectively in the direction of arrow 50 relatively to the surface 1 of the substrate 100. Thus also the plasma jet 10 and the laser beam 20 are guided in the direction of arrow 50 relatively to the surface 1 of the substrate 100.
(13) In this and the following figures the powder 20 is fed to the plasma jet 10 outside of the processing head 11. However, this is a not limiting factor of the invention. The powder 20 may be fed to the plasma eventually forming the plasma jet 10 in any way known to the person skilled in low-temperature plasma spraying. Likewise, it is not limiting to the invention that the laser beam 30 is directed onto the substrate 100 directly by the laser 31 and that the laser 31 is moved relatively to the surface 1. It is relevant for the method that the laser beam 30 impinges on the substrate 100 and that the laser beam 30 moves relatively to the surface 1, irrespectively of where the laser beam 30 is generated and how it is eventually directed onto the substrate 100.
(14) FIG. 2 shows a top view of a surface 1 of a substrate 100; the top view corresponds to an embodiment of the method as shown in FIG. 1. The laser incidence region 35 is shown, i.e. the region in which the laser beam 30 (see FIG. 1) impinges on the substrate 100; the shown circular shape of the laser incidence region 35 is not limiting to the invention. A part of a defined region 37 to be coated is also shown. The laser incidence region 35 is guided in the direction of arrow 50 across the defined region 37 and causes a heat input into the substrate 100 there. Therefore the laser incidence region 35 leaves behind a preheated region 36 on the surface 1 of the substrate 100, when moved in direction of arrow 50, wherein the preheated region 36 has not yet been impinged with powder 20 (see FIG. 1). The plasma jet 10, shown in FIG. 1 impinges on the surface 1 of the substrate 100 in a plasma incidence region 15 shown here to be of circular shape; however this circular shape is not limiting to the invention. The laser incidence region 35 and the plasma incidence region 15 have a defined relative position R to each other. The preheated region 36, which has not yet been impinged with powder 20, is located between the plasma incidence region 15 and the laser incidence region 35. If the plasma jet 10, and therefore also the plasma incidence region 15, is moved in direction of arrow 50 across the surface 1, a powder 20 is deposited along a trace S of the plasma incidence region 15 on the surface 1. With this movement the plasma incidence region 15 also sweeps over the respective preheated region 36, since the plasma jet 10 follows the laser beam 30. The plasma incidence region 15 follows the laser incidence region 35. According to the explanations above, a good adhesion can develop between the powder 20 deposited in the preheated region 36 and the surface 1 of the substrate 100, since, among other things, a difference in temperature between the powder particles in the plasma jet 10 and the preheated region 36 is reduced by preheating the region 36. Thus the structure 2, shaped here as a line with a width 3, is finally formed on the surface 1 of the substrate 100.
(15) Such a decrease of the difference in temperature between the powder particles in the plasma jet 10 and a corresponding region 16 does not occur in regions 16 outside of the preheated region 36, so that a good adhesion of the powder particles on the substrate 100 does not develop in the regions 16. The deposited powder 20 can be easily removed from these regions 16 by known methods.
(16) As mentioned at the beginning, line widths 3 are possible with the method according to the invention which are significantly smaller than the line widths achievable by a low-temperature plasma jet alone, i.e. without using a laser beam. This is so, because focusing the laser beam 30 on corresponding smaller diameters, which correspond approximately to the desired line width 3, is easier than a corresponding focusing of the plasma jet 10. Accordingly, in FIG. 2, a diameter DP of the plasma incidence region 15 is shown larger than a diameter DL of the laser incidence region 35.
(17) FIG. 3 to a large extent corresponds to FIG. 1. However, in the embodiment shown in FIG. 3, the laser beam 30 is directed through the plasma jet 10 onto the surface 1 of the substrate 100. The laser beam 30 impinges on the surface 1 of the substrate 100 outside of the plasma jet 10. In a top view an arrangement like in FIG. 2 would result. In the embodiment of the method shown in FIG. 3, a laser incidence region 35 defined by the laser beam 30 on the substrate 100 is located, relative to the direction of movement 50, in front of the plasma incidence region 15, so that the plasma jet 10 follows the laser incidence region 35 in this embodiment, too. In addition to a heat input into a region of the substrate 100, the laser beam 30 here can also heat powder particles which traverse the laser beam 30 within the plasma jet 10. This additional heating of the powder particles leads to a delay of the solidification of the powder particles after their impact on the substrate 100, as already mentioned above.
(18) FIG. 4 shows a further embodiment of the method and apparatus, which are similar to the one shown in FIG. 1. Most of the elements shown have already been discussed in the context of FIG. 1. For clarity reasons, plasma jet 10 and laser beam 30 have been shown larger compared with FIG. 1. Furthermore, a density profile 22 of the powder 20 in the plasma jet 10, and the plasma incidence region 15 determined by the density profile 22 are shown in FIG. 4. In this embodiment, the laser beam 30 is directed onto a region of the surface 1 of the substrate 100, which has already been impinged with powder 20. More precisely, the laser beam 30 is directed into the plasma jet 10 such that it impinges on a leading slope 22F of the density profile 22, if considered in direction 50 of a movement of the plasma jet 10 relative to surface 1. Therefore a thin powder layer 2d, which has already been deposited on the substrate 100 in this leading slope 22F, is impinged with laser radiation. This leads to a heat input into the powder particles in the thin powder layer 2d. This heat input counteracts the heat drain from these powder particles to the substrate 100 und therefore delays a solidification of the melted material of the powder particles, as mentioned above, so that finally the well adhering structure 2 is built on the surface 1 of the substrate 100.
(19) FIG. 5 shows a top view of the surface 1 of the substrate 100, corresponding to an embodiment of the method shown in FIG. 4. All elements shown have already been discussed in FIG. 2, which is a corresponding representation for an embodiment of the method shown in FIG. 1. In contrast to FIG. 2, the laser incidence region 35 is located within the plasma incidence region 15 in FIG. 5. A preheated region 36, like in FIG. 2, does not exist here, since the heat input in the laser incidence region 35 occurs, as shown in FIG. 4, into powder which has already been deposited on the surface 1. A requirement for the embodiment shown in FIGS. 4 and 5 is that the powder 20 is able to absorb the laser light sufficiently. The substrate 100, on the other hand, may be transparent for laser light in this embodiment.
(20) FIG. 6 shows an embodiment of the apparatus 300 according to the invention. A processing head 11 has a nozzle 12 for forming a plasma jet 10 out of a plasma. A plasma generator known to those skilled in the art may be used for generating the plasma. A laser 31 is attached to the processing head 11. The laser 31 is adjustable by an actuator 32, so that in particular the relative position R between the plasma incidence region 15 and the laser incidence region 35 discussed above can be set. The laser may be a semiconductor laser.
(21) FIG. 7 shows a further embodiment of the apparatus 300 according to the invention. Some of the depicted elements have already been discussed in the context of FIG. 6. An end 33e of an optical fiber 33 is attached to a holder 33h on the processing head 11. The holder 33h is adjustable by an actuator 32, so that in particular the relative position R between the plasma incidence region 15 and the laser incidence region 35 discussed above can be set. Moreover, this embodiment provides a coupling-out optics 34 for coupling out the laser light from the optical fiber 33. In this embodiment the coupling-out optics 34 is mounted on the processing head 11. The laser light is fed into the optical fiber 33 by a laser 31 in a way known to the skilled person. The laser may be a semiconductor laser.
(22) Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, such modifications are intended to be within the spirit and scope of the invention as claimed. It also is understood that the foregoing description is illustrative of the present invention and should not be considered as limiting. Therefore, other embodiments of the present invention are possible without departing from the spirit and scope of the present invention as claimed.
