DE102018206890A1 - A method and apparatus for laser cladding a surface area of a substrate and a job-welded component - Google Patents

Abstract

The invention proposes a method for laser beam deposition welding of a surface region (1) of a substrate (2) which emits at least two laser radiation (3, 4) of different wavelength, melting the surface region (1) of the substrate (2) by means of the laser radiation (3 , 4) and supplying a welding material (5) to the molten surface region (1) of the substrate (2).
In addition, an on-order welded component with such a method and an apparatus for laser cladding, comprising at least two laser sources (7, 8) for emitting at least two laser radiations (3, 4) of different wavelength for melting a surface region (1) of a substrate (2) specified ,

Description

The invention relates to a method for laser cladding of a surface region of a substrate, a device for laser deposition welding and a contract welded component.

Laser deposition, also referred to as laser metal deposition (LMD), is one of the methods of hardfacing, in which on a workpiece (substrate) a surface application by applying an additional material (welding material) takes place with simultaneous melting.

The energy source used is a laser which is suitable for heating the material of the substrate locally in a surface area and melting it to form a molten bath. In synchronism with the melting of the material of the substrate, the welding material is supplied to the surface area and also melted, whereby it connects to the material of the substrate. The welding material is often in powder form, for. B. supplied as metal powder, or in the form of a wire.

Laser deposition welding is a suitable method, workpieces such as components of gas or steam turbines, eg. As turbine blades, which are exposed during their use significant thermal, mechanical and / or chemical stresses to repair. U. a. therefore laser cladding is of great economic interest. A method and a device for Laserstrahlauftragschweißen of turbine components, for example, from DE 10 2014 210 652 A1 known.

However, the hot crack susceptibility of welded-on workpieces has proved problematic. This applies more to workpieces made of nickel-based superalloys, in particular workpieces made of nickel-based superalloys with a large proportion of intermetallic phase, such as. B. Alloy 247 or Rene 80 , Hot cracks lead to damaged workpieces and increase the reject rate.

Against this background, it is an object of the invention to provide an improved method and an improved apparatus for laser deposition welding, with which the mentioned disadvantages can at least be reduced or even completely eliminated.

This object is achieved by the subject matters of the independent claims. Advantageous developments of the invention are specified in the dependent claims.

The basic idea of the invention is to use laser radiation of different wavelengths for melting the surface area of the substrate to be welded on. As a result, the formation of a fine-grained structure can be promoted, whereby the formation of hot cracks can be reduced. Overall, there is an improvement in the weldability of hard-to-weld nickel base superalloys.

An inventive method for laser cladding a surface region of a substrate comprises emitting at least two laser radiations of different wavelengths, for. B. a first and a second laser radiation, a melting of the surface region of the substrate by means of the laser radiation and supplying a welding material to the molten surface region of the substrate.

The emitting of the laser radiation can take place simultaneously or alternately, preferably without interruption, alternately. For example, the associated laser sources can be switched on and off alternately so that in each case only one laser radiation reaches the surface region of the substrate.

In other words, in the surface region of the substrate to which the welding material is to be applied, a molten bath is formed by irradiation with at least two laser radiations of different wavelengths into which the welding material is introduced.

The welding material may preferably be supplied in powder form. For example, the welding material and the laser radiation can be supplied together to the surface region of the substrate by means of a nozzle or a coating head, with welding material and the laser radiation being conducted coaxially. Optionally, a shell of inert gas, for. As helium, argon and / or nitrogen to be placed around the welding material and / or the molten surface area of the substrate. The protective gas can also be supplied by means of the nozzle.

By combining the different wavelengths, different melt pool geometries can be generated. Due to the different absorption and heat conduction conditions at the melt surface for the different wavelengths, the solid-liquid phase boundary (solidification front or melt front) forms geometrically different depending on the wavelength.

This effect can be used to influence the nucleation and / or solidification at the solid-liquid phase boundary of the molten bath, so that a fine-grained microstructure can be obtained, which has a lower hot cracking tendency and therefore can solidify largely crack-free.

As a result, improved material properties of the components welded by means of the method according to the invention can be achieved in comparison to conventionally welded components. Material can be saved and the reject rate can be reduced.

The method can be used in particular for the similar coating repair of turbine blades made of a nickel-base superalloy with a large proportion of intermetallic phase. The method is particularly suitable for components with large dimensions, because they can be repaired material-saving and with high quality by the process.

According to various embodiments, a first laser radiation may have a wavelength in the visible spectral range, i. H. in the range of 380 nm to 780 nm, with a wavelength in the green-blue spectral range of 400 nm to 540 nm preferred and a wavelength of 515 nm is particularly preferred.

A second laser radiation may have a wavelength in the near infrared spectral range, i. H. in the range of 1030 nm to 1070 nm.

Particularly preferably, a first laser radiation has a wavelength in the range from 380 nm to 780 nm, in particular 515 nm, and a second laser radiation has a wavelength in the range from 1030 nm to 1070 nm.

The combination of laser radiation of the spectral ranges mentioned allows a particularly good influence on the Schmelzbadgeometrie and the achievement of a particularly fine-grained structure at the solid-liquid phase boundary. In addition, laser radiation in the green-blue spectral range of highly reflective materials, such. As copper, are particularly well absorbed, so that even substrates made of such materials and welding materials can be well order welding from such materials.

According to further embodiments, at least one laser radiation can be pulsed. Preferably, both the first and the second laser radiation can be pulsed. The pulse duration can each be in the range from 200 ms to 1000 ms. In addition, the pulses of the first and second laser radiation may overlap in time or completely or partially and / or alternate.

By means of the pulsation, the solid-liquid phase boundary and thus the solidification conditions can be additionally influenced. Through a changeover circuit of the first and second laser radiation, a quasi-continuous (cw, continouos wave) laser radiation can be generated, so that the energy input can also take place continuously. In other words, the pulses can be or become coordinated with one another in such a way that they complement each other or alternate without gaps, ie. H. that at a certain time in each case only the first laser radiation or the second laser radiation is emitted and a quasi cw laser radiation results.

According to further embodiments, the laser radiation can be coupled by means of an optical device in the surface region. A preferred optical device is a mirror, more preferably a dichroic mirror. A dichroic mirror serves to transmit or reflect different wavelength ranges. As a result, an alternating impingement of the laser radiation on the surface region of the substrate can be made possible even if the laser radiation of different wavelengths is emitted simultaneously.

According to further embodiments, at least the surface area of the substrate and the welding material may have the same composition. It can therefore be carried out, for example, a similar coating repair. Due to the same composition, similar absorption and heat conduction ratios result so that an improved weld joint is available.

According to further embodiments, at least the surface region of the substrate can comprise a nickel-base super alloy or consist of a nickel-base super alloy. Alternatively or additionally, the welding material may also comprise a nickel-base superalloy or consist of a nickel-base super alloy. The nickel-base superalloy may be, in particular, a nickel-base superalloy having a large proportion of an intermetallic phase, e.g. B. Alloy 247 or Rene 80 , act.

According to further embodiments, the substrate may be a turbine component, for. As a gas or steam turbine component, such as a turbine blade, z. B. a Turbinenleit- or turbine blade.

An inventive apparatus for laser deposition welding has at least two laser sources for emitting at least two laser radiations of different wavelengths, for. B. a first and a second laser radiation, for melting a surface region of a substrate. The at least two laser sources can be designed for the simultaneous and / or alternating emission of the laser radiation.

In other words, the laser sources are arranged so that the two laser radiations are emitted in the direction of the surface region of the substrate to be welded on.

In addition, the apparatus may include a feeder for supplying a welding material to the surface area of the substrate. Thus, the feeder serves to supply an additional material (welding material), which is melted during deposition welding and applied to the surface region of the substrate. The welding material, which is advantageously in powder form, may be provided in a dedicated container mounted on a conveyor system and delivered by a conduit to the feeder.

Preferably, the feeder can be used as a nozzle, e.g. B. as a slot or nozzle, be formed. In addition, the laser radiation can be conducted to the surface region of the substrate by means of the nozzle. In other words, a nozzle can be used from which both the welding material and the laser radiation are emitted. Preferably, the welding material and the laser radiation can be emitted coaxially with each other.

Optionally, the device may comprise a device for supplying a protective gas. For example, the protective gas can also be supplied via the nozzle. The protective gas can be supplied in such a way that a protective gas envelope is formed around the welding material and the laser radiation.

The device according to the invention is advantageously designed for laser deposition welding of a nickel-base superalloy. Preferably, both the surface region of the substrate and the welding material comprise a nickel-base superalloy, i. H. It is a similar laser deposition welding.

The device according to the invention is u. a. for the manufacture, repair or reprocessing of turbine components, eg. As gas or steam turbine components, suitable. These may, for example, be turbine guide or turbine blades.

The device according to the invention may be suitable, for example, for carrying out the method according to the invention explained above. Therefore, the above explanations serve to explain the method according to the invention also for the description of the device according to the invention. The advantages of the device according to the invention correspond to those of the method according to the invention and its corresponding variants.

According to various embodiments, a first laser radiation may have a wavelength in the range of 380 nm to 780 nm, preferably a wavelength of 515 nm, and / or a second laser radiation may have a wavelength in the range of 1030 to 1070 nm.

According to further embodiments, at least one laser radiation, preferably the first and the second laser radiation, may be pulsed. The pulse duration of at least one pulsed laser radiation, preferably all pulsed laser radiation, may be in the range of 200 ms to 1000 ms. The pulses can be designed so that pulses of the first laser radiation and pulses of the second laser radiation overlap in time or completely or partially and / or alternate.

According to further embodiments, the device may comprise an optical device, preferably a dichroic mirror, for coupling the laser radiation into the surface region of the substrate.

An inventive order-welded component, in particular a turbine component, such as. As a turbine vane or turbine blade, is welded by one of the methods described above.

Overall, the present invention makes it possible to achieve the solidification of a fine-grained microstructure at the solid-liquid phase boundary and, concomitantly, an improvement in weldability, especially in hard-to-weld nickel base super alloys such as Alloy 247 or Rene 80 , In addition, improved material properties of the component compared to a conventionally welded component are achieved, it can be saved material and the scrap rates for service components can be reduced.

Further features, properties and advantages of the present invention will be explained in more detail below with reference to exemplary embodiments with reference to the attached figures. All features described above and below are advantageous both individually and in combination with one another. It should be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following description is therefore not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

The figures are not necessarily true to detail and to scale and may be enlarged or reduced in size to provide a better overview. Therefore, functional details disclosed herein are not intended to be limiting, but merely illustrative, which provides guidance to those skilled in the art to variously employ the present invention.

As used herein, the term "and / or" when used in a series of two or more elements means that each of the listed elements may be used alone, or any combination of two or more of the listed elements may be used. For example, when describing a composition containing components A, B and / or C, composition A may be alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C are included in combination.

• 1 eine schematische Darstellung einer beispielhaften Vorrichtung zum Laserauftragschweißen mit einer ersten Laserquelle;
• 2 eine schematische Darstellung einer beispielhaften Vorrichtung zum Laserauftragschweißen mit einer zweiten Laserquelle;
• 3 eine schematische Darstellung einer Ausführungsform einer erfindungsgemäßen Vorrichtung;
• 4 ein Fließdiagramm einer Ausführungsform des erfindungsgemäßen Verfahrens;
• 5 eine schematische Darstellung des sich ausbildenden Schmelzbades und der Fest-Flüssig-Phasengrenze bei Durchführung eines erfindungsgemäßen Verfahrens und
• 6 eine schematische Detaildarstellung der Fest-Flüssig-Phasengrenze bei Durchführung eines erfindungsgemäßen Verfahrens.

Show it:

• 1 a schematic representation of an exemplary apparatus for laser deposition welding with a first laser source;
• 2 a schematic representation of an exemplary apparatus for laser cladding with a second laser source;
• 3 a schematic representation of an embodiment of a device according to the invention;
• 4 a flow diagram of an embodiment of the method according to the invention;
• 5 a schematic representation of the forming molten bath and the solid-liquid phase boundary when performing a method according to the invention and
• 6 a schematic detail of the solid-liquid phase boundary when performing a method according to the invention.

In 1 is a device 6 for laser cladding according to the prior art, by means of a welding material 5 on a surface area 1 a substrate 2 applied and can be connected cohesively.

The device 6 has a first laser source 7 on, for emitting a first laser radiation 3 is formed with a first wavelength. The first laser radiation 3 is by means of a nozzle 13 in the direction of the surface area 1 of the substrate 2 conducted, so that in the surface area 1 the material of the substrate 2 is melted and a melt 10 formed. The molten bath 10 is from a solid-liquid phase boundary 12 limited.

The nozzle is with a reservoir 9 for storing the powdery welding material 5 connected. For cladding, the powdered welding material 5 from the reservoir 9 to the nozzle 13 directed and together with the first laser radiation 3 to the surface area 1 of the substrate 2 passed, with the welding material 5 is also melted. The welding material 5 and the first laser radiation 3 are preferably emitted coaxially.

The nozzle 13 can over the surface area during buildup welding 1 of the substrate 2 be moved, so that also the area of the molten bath 10 migrates and becomes a solid-liquid phase boundary 12 between the already applied welding material 11 and the molten bath 10 formed.

2 shows another device 6 for laser cladding according to the prior art. Unlike the device 6 according to 1 is used instead of the first laser source 7 a second laser source 8th used so that instead of the first laser radiation 3 a second laser radiation 4 with one of the first laser beams 3 emitted deviating wavelength and the formation of the molten bath 10 and for melting the welding material 5 is being used.

3 shows a schematic representation of an embodiment of a device according to the invention 6 , The inventors have recognized that the absorption of laser radiation 3 . 4 as well as the heat conduction and thus also the formation of the molten bath 10 as well as the location of the solid-liquid phase boundary 12 among other things, on the wavelength of the laser radiation used 3 . 4 is dependent.

By combining a first laser radiation 3 and a second laser radiation 4 with divergent wavelengths, the formation of the molten bath 10 and the solid-liquid phase boundary 12 positively influenced, so that a fine-grained structure in the applied welding material 11 can be achieved, which is a has significantly lower tendency to hot cracking. The build-up welding can thereby be carried out with high quality, so that reject components can be avoided.

The exemplary device according to the invention 6 according to 3 has a first laser source 7 and a second laser source 8th on, giving a first laser radiation 3 with a first wavelength and a second laser radiation 4 can be emitted at a second wavelength. Both laser beams 3 . 4 become the formation of the molten bath and the melting of the welding material 5 how to the 1 and 2 described used.

In the exemplary embodiment, the first laser radiation 3 a wavelength in the range of 380 nm to 780 nm, preferably a wavelength of 515 nm, ie a wavelength in the green-blue spectral range, on. The wavelength of the second laser radiation 4 is in the range of 1030 nm to 1070 nm, ie in the near infrared range. Both the first laser radiation 3 as well as the second laser radiation 4 are pulsed, with the pulse duration in the range between 200 ms and 1000 ms can be. The pulses can be or are coordinated with one another in such a way that they complement or alternate with one another, ie that in each case only the first laser radiation is at a given time 3 or the second laser radiation 4 is emitted and a quasi cw laser radiation results.

The device according to the invention 6 may be disposed in a chamber (not shown) containing a nitrogen or inert gas atmosphere to trap trapped air in the deposited weld material 11 counteract. For coupling the first and second laser radiations 3 . 4 in the surface area 1 of the substrate 2 For example, an optical device, such as a dichroic mirror, may be present. In addition, the device can 6 known in the art components such. B. fiber optic cable and deflecting mirror have to influence the laser radiation 3 . 4 exhibit.

In 4 an embodiment of a method according to the invention for producing a component according to the invention is shown as a flow chart. In the exemplary embodiment, the component is a turbine blade of a gas turbine, at least in the surface region 1 consists of a nickel base superalloy. On the surface area 1 The turbine blade should be a welding material 5 , which is also made of a nickel-base superalloy, can be custom-welded for repair. Thus, a similar coating repair is performed by means of laser deposition welding.

In a first step S1 becomes the turbine blade to be repaired 1 provided and so on the device 6 positioned that the laser radiation 3 . 4 on the surface area to be repaired 1 the turbine blade and the welding material 5 can be welded on order. In a second step S2 The powdered welding material from the reservoir 9 to the nozzle 13 transported and onto the surface area 1 applied to the turbine blade.

In a third step S3 becomes in the surface area 1 a molten bath 10 trained, the welding material 5 melted and with the material of the surface area 1 merged. For this purpose, by means of the first and second laser source 7 . 8th the first and second laser radiation 3 . 4 alternately emitted. On the properties of the first and second laser radiation 3 . 4 Reference is made to the above statements.

The steps S2 and S3 can be performed simultaneously, since the first and second laser radiation 3 . 4 as well as the welding material 5 through the nozzle 13 be passed and the welding material 5 already at the moment of application to the surface area 1 melts.

In a fourth step S4 The order-welded turbine blade is removed. The steps S2 and S3 can be repeated, eg. B. by a thickness of the applied welding material 11 to increase. Optionally, the nozzle 13 with respect to the surface area 1 to be moved. This allows a flat application of the welding material 5 be enabled.

To illustrate the means of the device according to the invention 6 as well as achievable by the method according to the invention shows advantages 5 a schematic representation of the forming molten bath 10 and the solid-liquid phase boundary 12 when carrying out a method according to the invention. In 6 is the solid-liquid phase boundary 12 shown enlarged (area A off 5 ).

By using two laser beams 3 . 4 With different wavelengths, two molten baths are formed, which form a common molten bath 10 overlap. The forming solid-liquid phase boundary 12 is therefore no longer to be regarded as a sharp boundary as in the sole use of a laser radiation with a wavelength, but rather forms a solid-liquid boundary region (hatched area in the 5 and 6 ). An alternating switching off and on of both laser beams 3 . 4 leads to a specific influence on the solid-liquid phase boundary and thus the Solidification conditions. By influencing the solid-liquid phase boundary 12 The nucleation can be specifically influenced, so that a fine-grained microstructure solidifies and improved material properties of the component compared to conventionally welded components can be achieved.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102014210652 A1 [0004]

Claims (17)

A method of laser cladding a surface area (1) of a substrate (2), comprising: Emitting at least two laser radiations (3, 4) of different wavelengths, - Melting of the surface region (1) of the substrate (2) by means of the laser radiation (3, 4) and - Supplying a welding material (5) to the molten surface region (1) of the substrate (2). Method according to Claim 1 , wherein the at least two laser beams (3, 4) of different wavelengths are emitted alternately. Method according to one of the preceding claims, wherein a first laser radiation (3) has a wavelength in the range of 380 nm to 780 nm, preferably a wavelength in the range of 400 nm to 540 nm, particularly preferably a wavelength of 515 nm, and / or a second Laser radiation (4) has a wavelength in the range of 1030 nm to 1070 nm. Method according to one of the preceding claims, wherein at least one laser radiation (3, 4), preferably the first and the second laser radiation (3, 4), is or will be pulsed. Method according to Claim 4 , wherein a pulse duration of at least one pulsed laser radiation (3, 4) is in the range of 200 ms to 1000 ms. Method according to Claim 4 or 5 , wherein pulses of the first laser radiation (3) and the second laser radiation (4) overlap and / or alternate. Method according to one of the preceding claims, wherein the laser radiation (3, 4) by means of an optical device, preferably by means of a dichroic mirror, are coupled into the surface region (1). Method according to one of the preceding claims, wherein at least the surface region (1) of the substrate (2) and the welding material (5) have the same composition. Method according to one of the preceding claims, wherein at least the surface region (1) of the substrate (2) and / or the welding material (5) comprise a nickel-base superalloy or consist of a nickel-base superalloy. Method according to one of the preceding claims, wherein the substrate (2) is a turbine component, in particular a turbine blade. Device (6) for laser beam deposition welding, comprising at least two laser sources (7, 8) for emitting at least two laser radiations (3, 4) of different wavelengths for melting a surface region (1) of a substrate (2). Device (6) according to Claim 11 , wherein a first laser radiation (3) has a wavelength in the range of 380 nm to 780 nm, preferably a wavelength of 515 nm, and / or a second laser radiation (4) has a wavelength in the range of 1030 nm to 1070 nm. Device (6) according to Claim 11 or 12 , wherein at least one laser radiation (3, 4), preferably the first and the second laser radiation (3, 4), is or are pulsed. Device (6) according to Claim 13 , wherein a pulse duration of at least one pulsed laser radiation (3, 4) is in the range of 200 ms to 1000 ms. Device (6) according to Claim 13 or 14 , wherein pulses of the first laser radiation (3) and the second laser radiation (4) overlap and / or alternate. Device (6) according to one of Claims 11 to 15 comprising an optical device, preferably a dichroic mirror, for coupling the laser radiation (3, 4) into the surface region (1) of the substrate (2). Welded component, in particular turbine component, welded by a method according to one of Claims 1 to 10 ,

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