DE102016222872A1 - Pre-heating of a workpiece during pre-coating by a laser - Google Patents

Abstract

By pre-heating by means of a laser preheating can be performed faster when coating with ceramic material.

Description

The invention relates to an apparatus and a method for preheating a workpiece prior to coating by a laser.

Turbine blades receive complex multi-layer coating systems such as corrosion protection layers, adhesion promoter layers, thermal barrier coatings (WDS). The WDS usually has ceramics, which are applied porous by atmospheric plasma spraying. To achieve higher hot gas temperatures so-called "segmented TBCs" are used, which are characterized by vertical cracks in the TBC. These cracks serve as expansion joints so that the layers do not chip off at high temperatures due to thermal stress.

In order to inject the "Segmented TBC", the blade must be preheated. The preheating improves the adhesion of the sprayed powder particles. As the sprayed powder particle cools, shrinkage stresses result, leading to the vertical cracks.

So far, the pre-heating of the substrate is performed by the burner itself for spraying the "Segmented TBC". The burner is operated without powder feed. The torch is guided in a pendulum motion over a small area of the workpiece until a certain temperature is reached. Thereafter, the powder feed is turned on and the preheated portion of the workpiece is coated. Successively, further parts of the workpiece are coated.

It is therefore an object of the invention to solve the above-mentioned problem.

The object is achieved by a device according to claim 1 and a method according to claim 2.

In the dependent claims further advantageous measures are listed, which can be combined with each other in order to achieve further advantages.

The figure shows schematically a device according to the invention.

The preheating of the workpiece by a time-consuming pendulum movement of the burner is performed by at least one laser. For this purpose, the burner is preceded by a laser beam whose power is preferably controlled by a pyrometer.

• - Die Temperatur des Werkstücks wird korrekt eingestellt.
• - Die Robustheit des Spritzprozesses wird durch eine homogene Vorheiztemperatur verbessert.
• - Die Vorschubgeschwindigkeit des Brenners kann variiert werden. Die Vorheiztemperatur ist immer konstant, da die Leistung des Lasers über das Pyrometer geregelt wird.
• - Die Prozesszeit wird verbessert und es werden Kosten gespart, da eine separate Vorheizzeit entfällt.

The use of the laser beam, the power of which is preferably controlled by a pyrometer, has the following advantages in the production of "segmented TBCs":

• - The temperature of the workpiece is adjusted correctly.
• The robustness of the injection process is improved by a homogeneous preheating temperature.
• - The feed speed of the burner can be varied. The preheat temperature is always constant as the power of the laser is controlled by the pyrometer.
• - The process time is improved and costs are saved, since a separate pre-heating time is eliminated.

The figure shows schematically a device 1 according to the invention.

The device 1 is inside or part of a coating plant in which a workpiece 4 is held or arranged to coat it.

The coating takes place on a surface 19 of the workpiece 4 ,

In the case of turbine parts, in particular gas turbine parts, nickel-based or cobalt-based workpieces 4 provided with a metallic and / or a ceramic thermal barrier coating.

This is done in particular by the use of a powdery coating material 22 coming from a powder reservoir 10 over a nozzle 7 on the surface 19 of the workpiece 4 is directed.

Processes for ceramic coating are APS, LPS or HVOF. This list is not limiting.

Preferably, zirconium oxide and / or pyrochlore, single-layered or double-layered, is sprayed.

As explained above, it is necessary to maintain a preheating to set up segmented ceramic thermal barrier coatings to give a temperature gradient. This is done by having in the device 1 a laser 17 is present, the laser beams 16 can radiate and very quickly and very effectively the workpiece 4 can preheat.

The preheating is preferably carried out in a first partial area 33 and coating in a second subarea 30 at the same time, the second partial area 30 even in advance by the laser 17 was heated. Subsequently, the preheated first part surface 33 coated.

This is done for the entire surface to be coated, with the entire surface divided into faces.

Claims (4)

Device (1) for coating and preheating a workpiece (4) during the coating, in which the device (1) has at least: a nozzle (7), in order to be able to apply coating material (22) from a coating reservoir (10) to the workpiece (4), at least one laser (17), the laser beams (16) can radiate, around the workpiece (4), which is coated by means of the nozzle (7), to be able to preheat especially during the coating preheat. Method for preheating a workpiece (4) during coating, in particular by means of a device according to Claim 1 in which a laser beam (16) of a laser (17) is directed during the coating onto the workpiece (4) in a device (1) in order to at least partially heat the workpiece (4), and thereafter a coating with a coating material (22 ) from a powder reservoir (10), which is directed via a nozzle (7) on the surface (19) of the workpiece (4) takes place. Method according to Claim 2 in which a ceramic layer is applied. Method according to Claim 2 or 3 in which the preheating of a first partial surface (33) and the coating in another second partial surface (30) occur simultaneously and then the preheated first partial surface (33) is coated.

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