METHOD FOR SELECTIVE LASER BEAM BRAZING

Abstract

Method for selective laser beam brazing of a substrate, comprising: Providing a powder (10) containing several parent core particles (20) and several hard solder particles (30); Setting the temperature of a laser source (170); Applying the laser source (170) to the powder (10); and Allow the heated powder to solidify, wherein the multiple parent core particles (20) are fused together by the majority of hard solder material (30) to form a desired solid component (130), Bonding the solidifying powder to a substrate, wherein the parent nucleus particles (20) are made from substrate material of a substrate.

Description

CROSS-REFERENCE TO RELATED REGISTRATIONS

[0001] The present application claims the advantage of US application number 15 / 054,603, filed on February 26, 2016, the entire contents of which are hereby incorporated by reference. GENERAL STATE OF THE ART 1. Field of invention

[0002] The present application relates to the manufacture of components as well as gas and steam turbines and in particular to a method for selective laser beam brazing. 2. Description of the state of the art

[0003] Additive manufacturing, or 3D printing, has recently been successfully used to directly "print" or manufacture components layer by layer. This manufacturing technology enables the optimization of component design. Additive manufacturing of components encompasses a wide range of materials and process techniques. Two key process techniques are selective laser sintering (SLS) and selective laser melting (SLM). Selective laser sintering (SLS) is an additive manufacturing technique that uses a laser as the power source to sinter powdered material. The laser is automatically directed to points defined by a three-dimensional model in space, fusing the material together to create a solid structure.Selective laser melting (SLM) is an additive manufacturing process that uses a three-dimensional model and energy in the form of a high-power laser beam to create the solid structure by fusing metal powders in a molten state. The main difference between selective laser sintering and selective laser melting is that in sintering, the material is not melted but heated to the point where bonds form between particles through diffusion, whereas in melting, the particles are completely melted and fused together in the molten state. A method for using a solder material with carbon structures is known from US patent 2015 / 0129564 A1. Systems and methods for the additive manufacturing and repair of metal components are known from WO patent 2014 / 074947 A2.

[0004] Both of these techniques, selective laser sintering and selective laser melting, have disadvantages. For example, selective laser sintering may not produce a completely dense component. After the selective laser sintering process is complete, voids may exist between the particles, requiring an additional process step, such as hot isostatic pressing (HIP), to compress the particles and eliminate the voids. In selective laser melting, each particle is melted and, upon resolidification, forms a specific crystal structure, size, and / or orientation that may not be optimized for the component. In particular, when the laser beam is applied in selective laser melting, a layer of particles is completely melted from a substrate.During resolidification, the orientation of the crystal microstructure in the substrate, which is melted in the process, can be directional, so that the properties of the layer may differ in the vertical and horizontal directions. For example, the tensile strength of the layer after resolidification may be higher in the horizontal direction than in the vertical direction. A technique that would fuse the particles together without melting the substrate material, resulting in complete densification and strength, is desirable. BRIEF DESCRIPTION OF THE INVENTION

[0005] In short, aspects of the present disclosure relate to a method for selective laser beam brazing.

[0006] A method for selective laser beam brazing is provided. The method involves providing a powder containing multiple parent core particles and multiple brazing particles, setting the temperature of an energy source, applying the energy source to the powder, and allowing the heated powder to solidify. The multiple parent core particles are fused together by the multiple brazing particles to form a desired component. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates parent core particles coated with a hard solder material, Fig. 2 illustrates parent core particles mixed with hard solder particles, Fig. 3 illustrates hard solder particles arranged against parent nucleus particles, forming conglomerate particles, Fig. Figure 4 illustrates parent core particles fused with hard solder material after selective hard soldering. Fig.Figure 5 illustrates an example of a selective laser process, and Fig. Figure 6 illustrates another example of a selective laser process. DETAILED DESCRIPTION

[0007] To overcome the disadvantages of using selective laser processes such as selective laser sintering and selective laser melting, as outlined in the section on the general state of the art, an intermediate-temperature process, selective laser beam brazing, is proposed. Brazing can be defined as a process that creates coalescence of materials by heating them to a temperature in the presence of a filler material with a melting point above 450°C (liquidus curve) and below the melting point (solidus curve) of the substrate material. When heat is applied from an energy source such as a laser, the filler material flows between the substrate material and is distributed by capillary action.This technique can be defined as an intermediate temperature process, since the temperature used can be above that used in laser sintering, but below that used in melting a layer of the substrate material.

[0008] To facilitate an understanding of the embodiments, substrates, and features of this disclosure, they are explained below with reference to an implementation in illustrative embodiments. However, embodiments of this disclosure are not limited to use in the systems or processes described.

[0009] The components and materials described below, which constitute the various embodiments, are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as those described herein are intended to be included within the scope of protection of embodiments of this disclosure.

[0010] With reference to the Fig.Reference 1-6 provides a method for selective brazing. In one embodiment, a powder 10 is produced with multiple parent core particles 20 and a plurality of brazing material or multiple brazing particles 30. The temperature of an energy source 170 is set. The energy source 170 is then applied to the powder 10. The heated powder is allowed to solidify. Programmed repetitions of melting and solidification layer by layer (similar to selective laser melting) additively produce a component 130. As a result of the selective brazing process, the multiple parent core particles 20 are fused together by the multiple brazing particles / the plurality of brazing material 30 to form a desired component 130.

[0011] At the in Fig.In the embodiment shown in Figure 1, the powder 10 is produced by coating the multiple parent core particles 20 with a majority of brazing material 30, such that a substantially uniform distribution of brazing material exists around the parent core particles 10. Such a coating can be achieved by methods known in powder coating production, including chemical vapor deposition and the melting of brazing material with a uniform mixture of parent core particles, followed by comminution to produce coated powder.

[0012] In another, in Fig. In the embodiment shown in Figure 2, the powder 10 is produced by mixing the multiple parent core particles 20 with multiple hard solder particles 30. The mixing results in a substantially random mixture of parent core particles 20 and hard solder particles 30.

[0013] In another, in Fig.In the embodiment shown in Figure 3, the powder 10 is produced by depositing several hard solder particles 30 opposite each parent core particle 20, resulting in several conglomerate particles 40. Such an arrangement can be achieved by methods known in powder production, including bonded powder, where a binder adheres particles together, and compound powder, agglomerated by pressure or heat (sintering). As shown in Fig. As can be seen in Figure 3, the conglomerate particle 40 has several hard solder particles 30 arranged against it. However, the parent core particle 20 is not coated by the several hard solder particles 30, i.e., there is no substantially complete distribution of hard solder particles 30 surrounding the entire surface of each parent core particle 20.

[0014] According to the brazing procedure defined above, the temperature of an energy source 170 is set to a temperature above the melting point (liquidus curve) of the brazing material particles 30, but below the melting point (solidus curve) of the parent core particles 20. As a result, the brazing material particles 30 melt, but the parent core particles 20 do not. Thus, the melting point of the brazing material particles 30 is below the melting point of the parent core particles 20. Due to the melting of the brazing material particles 30 and the distribution of molten brazing material by capillary action around a group of parent core particles 20, the subsequently solidified brazing material 30 fuses the multiple parent core particles 20 together. Fig.4 illustrated by the melted and resolidified multiple brazing particles 30 fused together parent core particles 20 after the selective brazing procedure applied to each of the manufacturing processes 1, 2 and 3 as described above.

[0015] Fine brazing alloy particles 30 in a range of approximately 10 to 60 µm would have a sufficient surface area to promote wetting and fusing by capillary action for the selective brazing procedure. Wetting can be defined as the ability of a liquid, for example, the molten brazing alloy particles 30, to maintain contact with a solid, such as the parent core particles 20, and with a previously deposited substrate, including solidified brazing alloy with embedded core particles.

[0016] In all of the Fig. 1, Fig. 2 and Fig.In the embodiments shown in Figure 3, the brazing alloy particles 30 fuse together with the parent core particles 20 after the molten brazing alloy material has been allowed to solidify with the heated core particle powder. A desired solid component 130 can be formed from the selective brazing process. However, in the embodiment shown in Figure 3, the brazing alloy particles 30 fuse together with the parent core particles 20 after the molten brazing material has been allowed to solidify with the heated core particle powder. A desired solid component 130 can be formed from the selective brazing process. Fig. As shown in Figure 1a, where the parent core particles 20 are coated with the hard solder material 30, a more uniform distribution of hard solder material 30 can be arranged between the parent core particles 20.

[0017] One embodiment of the method involves producing relatively high-temperature parent core particles 20 coated with a hard solder alloy material 30. In this embodiment, the parent core particles 20 have a melting point above 2000°C. Table 1 lists some candidate materials for high-temperature core particles 20 (substrate material) and a corresponding hard solder material 30. These powders may be of interest for additive manufacturing in high-temperature applications. Some of these powders, such as nickel on yttrium oxide-stabilized zirconium oxide, can be used as thermal barrier coatings for additive application to superalloy substrates. This table is exemplary and not exhaustive. Numerous other examples are possible.

[0018] Table 1 - Candidate powders for selective laser beam brazing of components that are useful with high-temperature core particles. Hard solder (coating) Liquidus curve (°C) Substrate (base material) Solidus curve (°C) nickel 1455 zirconium oxide stabilized with yttrium oxide ~2600 nickel 1455 graphite 3642 nickel 1455 W, Mo, Cr2O3,Cr3C2, WC, TiC, silicon dioxide, etc. Different Ni-P (e.g. Ni-7,9P) 890 diamond 3642 Ni-P (e.g. Ni-7,9P) 890 W 3422 Ni-P& Ni-B (e.g., BNi-7,9P) 890 Si-C 2730

[0019] The brazing alloy powder 10 with the multiple brazing particles 30 can also contain a melting point depressant to produce a brazing alloy. Melting point depressants are used to lower the melting point of a material. This can be desirable because a wider variety of materials than the brazing alloy can be used, including those whose melting points are relatively close to that of the parent core particles 20. Examples of melting point depressants are boron, phosphorus, and silicon. As an example, Table 1 shows that a brazing alloy of nickel and phosphorus contains a melting point of 890°C, whereas the melting point of nickel alone is 1455°C. The nickel-phosphorus combination substantially lowers the melting point to about 565°C.In this case, for the described selective brazing process, the temperature of the energy source can be set to a lower temperature to melt the nickel-phosphorus combination compared to melting nickel particles without a melting point depressant. After selective laser beam brazing, the component can undergo a post-process heat treatment to diffuse the melting point depressant and to optimize its properties.

[0020] The brazing alloy powder 10 can contain a wetting agent to produce a brazing alloy. As described above, wetting is the ability of the brazing alloy particles to maintain contact with the parent core particles 20, so that the molten brazing alloy flows well between the parent core particles and with the previously deposited substrate. Zirconium and silicon are examples of wetting agents. Silicon can also be used as a melting point lowerer. Thus, silicon can be used in the brazing alloy to fulfill the dual functionality of a melting point lowerer and a wetting agent.

[0021] Fig.Figure 5 illustrates a selective laser beam processing method 100 for the additive manufacturing of a component 130. A powder 10 is delivered to a surface by a powder feed / builder piston 110 and a roller 180. The roller 180 moves a layer of powder 10 to a builder powder bed 150. An energy source, such as a laser 170, scans a section of the powder bed 150. The scanned section of the powder bed 150 corresponds to a layer of a three-dimensional representation of a component 130 being manufactured. After the layer has been scanned, a feed / builder piston 110 moves the builder powder bed 150, together with the component 130, down the thickness of one layer. The three-dimensional representation of the component 130 being manufactured can be stored in a scanner system 160.

[0022] For the selective brazing process, the powder would comprise 10 parent core particles 20 and brazing alloy particles 30. The laser 170 would be set to a temperature above the melting point (liquidus curve) of the brazing alloy particles 30, but below the solidus temperature of the parent core particles (substrate material) 20.

[0023] While that in Fig. Since the selective laser processing methods described in section 5 can be used in an additive manufacturing process, the selective brazing process can also be used to produce components from powder-fed deposits instead of exclusively pre-placed layer by layer. Fig. Figure 6 illustrates another selective laser processing method (200) that produces the component using powder feed, so that the process can be continuous and is not carried out layer by layer, as in the process of Fig.Figure 5 shows that, for example, the powder can be fed through a nozzle (210) onto a substrate (220) onto which an energy source (270) is focused. The brazing alloy particles in the powder would be melted by the laser (270) and distributed between the parent core particles, generating a melt pool (230) containing molten brazing alloy and solid parent core particles, as described above. After solidification, a resulting deposit of material can be formed, which could be in the desired shape of a component.

[0024] At the in Fig. In the embodiment shown in Figure 5, a laser 170 is used as the energy source. However, those skilled in the art understand that other energy sources capable of reaching a temperature sufficient to melt several brazing particles 30 can be used for the selective brazing process. Other examples of energy sources include a plasma arc beam and an electron beam.

[0025] While embodiments of the present disclosure have been disclosed in exemplary forms, the person skilled in the art understands that many modifications, additions and deletions can be made to them without deviating from the idea and scope of protection of the invention and its equivalents, as set out in the following claims.

Claims

[1] Method for selective laser beam brazing of a substrate, comprising: Providing a powder (10) containing several parent core particles (20) and several hard solder particles (30); Setting the temperature of a laser source (170); Applying the laser source (170) to the powder (10); and Allow the heated powder to solidify, wherein the multiple parent core particles (20) are fused together by the majority of hard solder material (30) to form a desired solid component (130), Bonding the solidifying powder to a substrate, wherein the parent nucleus particles (20) are made from substrate material of a substrate. [2] Method according to claim 1, wherein the temperature of the energy source (170) is set to a temperature above the melting point (liquidus curve) of the brazing particles (30) and below the solidus curve of the parent core particles (20), so that the brazing particles (30) melt and the parent core particles (20) do not melt. [3] Method according to claim 1, wherein the manufacturing includes coating each of the multiple parent core particles (20) with a hard solder material (30). [4] Method according to claim 1, wherein the manufacturing includes mixing the multiple parent core particles (20) with the multiple brazing particles (30). [5] Method according to claim 1, wherein the manufacturing process includes arranging brazing particles (30) against each parent core particle (20) such that several conglomerate particles (40) are formed. [6] Method according to claim 1, wherein the multiple parent nucleus particles (20) each have a diameter between 10 and 60 µm. [7] Method according to claim 1, wherein the parent core particles (20) have a melting point above 2000°C. [8] The method of claim 1, wherein the application includes: Scanning, with the energy source (170), several layers generated from a three-dimensional description of the component (130) on the surface of a powder bed (150), and Focusing the energy source (170) onto the powder (10) that has been fed onto a substrate (220) to produce a deposition of material. [9] Method according to claim 1, wherein the multiple brazing particles (30) comprise nickel and the multiple parent core particles (20) comprise yttrium oxide stabilized zirconium oxide. [10] Method according to claim 1, wherein the multiple brazing particles (30) contain a brazing alloy with a melting point depression material, wherein the melting point depression material is selected from the group consisting of boron, phosphorus and silicon, wherein, after permission, the method includes subjecting the component (130) to a post-process heat treatment to diffuse the melting point depression material.

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