Patent Application
20170129053
This application claims priority to German Patent Application No. 10 2015 222 141.5 filed on Nov. 10, 2015, the entirety of which is incorporated by reference herein.
The invention relates to a holding device for a substrate and a method for coating a top surface of a substrate.
It is known that phase transformations may occur when a substrate coating with hard substance particles is applied by means of a generative laser method, which leads to instabilities. Another challenge is to maintain a desired geometry of the coating.
What is known from EP 0 349 501 A1 is a device that describes a generative laser method for applying a coating.
The present invention is based on the objective to provide an improved holding device and an improved method for coating a top surface of a substrate.
According to the invention, this objective is achieved by the arrangement with the features as described herein.
The holding device serves for receiving a substrate during the performance of a generative laser method for applying a hard substance particle coating to the top side of the substrate. Here, the wall of the substrate is completely surrounded by a thermoconductive wall of the holding device at least in the area of the top side of the substrate. For example, the wall of the substrate can be completely enclosed by the holding device.
At that, the wall of the holding device protrudes beyond the top side of the substrate with a projection, which is at least in the size range of the coating thickness to be applied. The circumferential projection can serve for providing a certain degree of stability to the coating during manufacture, in particular in the liquid or in the malleable state. In particular the wall of the holding device is arranged so as to be perpendicular to the top side of the substrate.
Thus, a laser-induced molten coating bath can be supported on the top side of the substrate through this arrangement of the wall of the holding device. In the horizontal cross-section, the coating has the shape of the substrate.
Since the wall of the holding device comprises a thermoconductive wall, a targeted temperature control, for example a targeted cooling, can be achieved during the application of the coating.
Thus, the holding device can serve for giving the coating a desired geometrical shape and at the same time for reducing the risk of a phase transformation (for example the formation of undesired phases) by targeted heat dissipation.
In one embodiment, the substrate can be spatially fixated by means of the wall of the holding device.
In one embodiment, the projection can have half to three times the size of the thickness of the coating to be applied.
In another embodiment variant, the holding device is adjusted to the substrate in such a precisely fitting manner that the distance between the wall of the holding device and the substrate is less than 0.2 mm in the area of the top side.
In one embodiment form, the wall of the holding device in particular comprises a material with a low weldability with respect to the used substrate material. In this manner, it can for example be avoided that the holding device is connected to the substrate while being heated by a laser. Such a material can for example be copper, aluminum, brass, bronze, or ceramic materials.
In another embodiment variant, the holding device, in particular the wall, comprises a material that has a high reflectance for laser light. In a generative laser method, the used laser light is thus reflected in all the places where the material of the holding device is present. However, it is not reflected particularly at the top side of the substrate, and can thus unfold its effect in a targeted manner in order to create a molten coating bath. Here, too, for example copper, brass or bronze can be used. At that, the material is to be selected with respect to the reflectance of the wavelength of the laser. Particularly copper has a high reflectivity with the typically used wavelengths, while the substrate absorbs the laser power well in this area.
Alternatively or additionally, it is also possible that the wall of the holding device comprises a material with a high thermal conductivity, in particular copper or aluminum. In this manner, an effective temperature control of the substrate can be achieved.
In order to improve the cooling of the substrate, in one embodiment the wall of the holding device can have an active cooling device for adjusting a temperature of the wall of the holding device—and thus also of the substrate. At that, for example the temperature of the wall of the holding device can be adjusted with a control device for the cooling device. Here, one possibility is that the cooling device is configured as a liquid cooling, in particular as a water cooling. Water has a high thermal capacity, so that it is well suited as a cooling agent. Principally, evaporative cooling by means of water or liquefied gases (for example nitrogen) is also possible.
In this manner, it is in particular possible to control the temperature of the wall of the holding device from room temperature up to several hundred degrees Celsius.
In one embodiment, the substrate is a structural component of a turbomachine, in particular a blade or a seal element.
This objective is achieved through a method as described herein.
At that, the method comprises the following steps:
a) providing the substrate;
b) masking the substrate with a holding device according to at least one of the claims 1 to 12;
c) creating a molten coating bath by means of laser deposition welding on the top side of the substrate;
d) implanting hard substance particles into the molten coating bath and/or the top side of the substrate by means of laser deposition welding, wherein the created molten coating bath is supported by the wall of the holding device, and the heat of the molten coating bath is at least partially dissipated by the holding device.
In the following, the invention is explained based on exemplary embodiments in connection to the figures.
The holding device 10 encloses the substrate 1 on four sides, while a coating 3 (see
In this embodiment variant, the holding device 10 is configured in one piece and has a cuboid-shaped outer contour. Further, the holding device 10 has a cuboid-shaped indentation that serves for receiving the substrate 1.
The cuboid-shaped indentation is delimitated on four sides (that is, completely) by a thermoconductive wall 11 of the holding device 10, i.e the wall 11 of the holding device 10 is oriented towards the substrate 1 during operation. The substrate 1 has an extension that is only minimally smaller than the extension of the indentation. In the present case, the distance between the substrate 1 and the wall 11 of the holding device 10 is less than 0.2 mm.
In alternative embodiments, the holding device 10 and also the substrate 1 can have a different shape. Thus, the horizontal cross-section of the substrate 1 can for example have a square, polyhedral or also a complex shape. However, in any case the walls 11 of the holding device 10 surround the substrate 1 on all sides.
As can be seen in
The substrate 1 is thus lowered in the vertical direction. The projection H is in the size range of the coating 3 to be applied. In some embodiment variants, the projection H can have half to three times the size of the thickness of the coating 3 to be applied. In this size range of the projection H, it is possible to support the molten coating at its sides.
The wall 11 can spatially fixate the substrate 1, in particular during the coating of the substrate 1.
In some embodiment variants, the wall 11 of the holding device 10 can comprise a material with at least one of the following characteristics: a low welding tendency, a high reflectance for laser light, or a high thermal conductivity. This material can particularly be copper.
In alternative embodiments, the cooling device 12 can also be integrated inside the wall 11 of the holding device 10. It is also possible that the cooling device 12 is arranged only in certain parts of the holding device 10.
The cooling device 12 can be a liquid cooling, in particular a water cooling, as in the embodiment variant that is shown here. By means of the cooling device 12, that is for example controlled by a control device 13, a temperature of the wall 11 of the holding device 10 can be adjusted. For example, the wall 11 of the holding device 10 can be temperature-controlled to room temperature.
Apart from the temperature, the temperature profile can also be adjusted by means of the control device 13, so that a targeted cooling is possible.
In a further embodiment variant, which is shown in
The laser serves for creating a molten coating bath at the surface 2 of the substrate 1. A first powder supply means serves for supplying a first powder, in particular MCrAlY, for creating the molten coating bath. The second supply means serves for supplying hard substance particles 4, in particular cBN particles.
In connection to
In a method for coating a top surface 2 of a substrate 1, at first the substrate 1 has to be provided. Next, the substrate 1 is masked with a holding device 10. This situation is shown in
Subsequently, a molten coating bath is created on the top side 2 of the substrate 1 by means of laser deposition welding, that is, by using a laser while a first powder is being supplied. The laser serves for the localized fuzing, at first of the top side 2 of the substrate 1. Into this molten bath, the powder is introduced. This powder, too, is molten by the laser, wherein further powder is supplied. The result of this is shown in
In a subsequent step, the hard substance particles 4 are implanted into the molten coating bath and/or into the top side 2 of the substrate 1 by means of laser deposition welding. At that, the greater part of the hard substance particles 4 is not molten. The hardened molten coating bath forms the coating 3 of the top side 2 of the substrate 1. This is shown in
The holding device 10 supports the created molten coating bath through the projection H of the wall 11, so that the coating 3 has the shape of the substrate in the cross-section perpendicular to the vertical direction, that is, in the horizontal cross-section.
The heat of the molten coating bath is dissipated at least partially through the holding device 10.
In embodiment variants of the holding device 10 that comprise an active cooling device 12, the temperature of the holding device 10 can be adjusted in a targeted manner. This can be used for controlling the heat dissipation in a targeted manner.
As is shown in
This arrangement is shown in
In this cross-section, the rotor blade 2 has a contour that is comprised of a wall and encloses a hollow space. The inner as well as the outer wall of the rotor blade 2 are respectively surrounded by a wall 11 of the holding device 10 at least in the area of the surface 2, that is, in the area of the rotor blade.
Thus, the holding device 10 is comprised of two parts also in this embodiment variant. Both parts are respectively shaped so as to be contoured correspondingly to the rotor blade. One part fits exactly into the inside of the rotor blade, and one part fits exactly around the outer circumference of the rotor blade.
In further embodiment variants that are not shown here, the holding device 10 can thus be adjusted to further contours of a top side 2 of a substrate 1 to be coated.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 222 141.5 | Nov 2015 | DE | national |
