Continuous additive manufacturing of high pressure turbines

Abstract

A method of manufacturing an object by additive manufacturing is provided. The method includes lowering a build platform having a given layer of build material to a powder disposed on a window. The powder is irradiated to form a subsequent layer corresponding to the given layer. The method then includes curing the subsequent layer, and lifting the build platform and the subsequent layer off the window. The steps are repeated until a desired object is formed.

Description

Technical Field

[0001] The present disclosure generally relates to an additive manufacturing apparatus and a method for additively manufacturing metal parts. More specifically, the present disclosure relates to an apparatus and method for repeatedly lowering an object to be additively manufactured into metal powder on a translucent surface and using light projection and / or a focused energy beam through the translucent surface to melt or consolidate the metal into layers of the object. Background Art

[0002] Compared to subtractive manufacturing methods, additive manufacturing processes generally involve the accumulation of one or more materials to make a net or near net shape (NNS) object. Although "additive manufacturing" is an industry standard term (ASTM F2792), additive manufacturing encompasses a variety of manufacturing and prototyping technologies known by various names, including free-form manufacturing, 3D printing, rapid prototyping / machining, etc. Additive manufacturing technology is capable of making complex components from a variety of materials. Generally, independent objects can be made from computer-aided design (CAD) models. A specific type of additive manufacturing process uses an energy beam, such as an electron beam or electromagnetic radiation, such as a laser beam, to sinter or melt powdered materials to produce a solid three-dimensional object in which the particles of the powdered material are linked together. Different material systems, such as engineering plastics, thermoplastic elastomers, metals, and ceramics are being used. Laser sintering or melting is a significant additive manufacturing process for the rapid manufacture of functional prototypes and tools. Applications include direct manufacturing of complex workpieces, patterns for investment casting, metal molds for injection molding and die casting, and molds and cores for sand casting. Prototyping objects to enhance communication and testing of ideas during the design cycle are other common uses of the additive manufacturing process.

[0003] Selective laser sintering, direct laser sintering, selective laser melting and direct laser melting are common industry terms used to refer to the production of three-dimensional (3D) objects by sintering or melting fine powders using a laser beam. For example, U.S. Patent No. 4863538 and U.S. Patent No. 5460758 describe conventional laser sintering techniques. More precisely, sintering is accompanied by fusing (condensing) powder particles at a temperature below the melting point of the powder material, while melting is accompanied by completely melting the powder particles to form a solid uniform mass. The physical processes associated with laser sintering or laser melting include heat transfer to the powder material, and then sintering or melting the powder material. Although laser sintering and melting processes can be applied to a wide range of powder materials, the scientific and technical aspects of the production route (e.g., sintering or melting rates, and the effects of processing parameters on microstructural evolution during the layer manufacturing process) are not well understood. The manufacturing method is accompanied by multiple modes of heat, mass and momentum transfer and chemical reactions that make the process very complicated.

[0004] Figure 1A diagram showing a cross-sectional view of an exemplary conventional system 100 for direct metal laser sintering ("DMLS") or direct metal laser melting (DMLM). The apparatus 100 builds an object (e.g., part 122) in a layer-by-layer manner by sintering or melting a powdered material (not shown) using an energy beam 136 generated by a source 120 (e.g., which may be a laser for generating a laser beam, or a filament that emits electrons when an electric current flows through it). The powder melted by the energy beam is supplied from a reservoir 126 and evenly spread on a powder bed 112 using a recoater arm 116 that travels in a direction 134 to maintain the powder at a level 118, and excess powder material extending above the powder level 118 is removed to a waste container 128. Under the control of an irradiation emission guide device such as a galvanometer scanner 132, the energy beam 136 sinters or melts cross-sectional layers of the built object. For example, the galvanometer scanner 132 may include a plurality of movable mirrors or scanning lenses. The speed of the laser scan is a key controllable process parameter that affects how long the laser power is applied to a particular point. Typical laser scan speeds are about 10 to 100 millimeters per second. The build platform 114 is lowered and another layer of powder is spread over the powder bed and the object is built, followed by continued melting / sintering of the powder by the laser 120. For example, the powder layer is typically 10 to 10 microns. The process repeats until the part 122 is completely built from melted / sintered powder material.

[0005] The laser 120 may be controlled by a computer system including a processor and a memory. The computer system may determine the scanning pattern of each layer and control the laser 120 to irradiate the powder material according to the scanning pattern. After the part 122 is manufactured, various post-processing procedures may be applied to the part 122. The post-processing procedures include, for example, removing excess powder by blowing or vacuuming. Other post-processing procedures include stress relief processes. In addition, thermal and chemical post-processing procedures may be used to finish the part 122.

[0006] Additive manufacturing by irradiating material through a translucent window against which the build material rests is generally referred to as a process such as constrained stereolithography when the illumination source is a laser, or digital light processing (DLP) when the illumination source is a digital light projector. These processes have an advantage over conventional powder bed processes in that the irradiated material is formed against the window, generally eliminating the need for certain support structures. However, constrained stereolithography and DLP are generally limited and do not work well with metal powders, coated metal powders, and metal slurries. Summary of the invention

[0007] The following presents a brief summary of one or more aspects in order to provide a basic understanding of these aspects. This summary is not an extensive overview of all aspects of the concept, and its purpose is neither to identify the key or important factors of all aspects, nor to describe the scope of any or all aspects. Its purpose is to present some concepts of one or more aspects in a simplified form as a prelude to a more detailed description presented later.

[0008] Aspects of the foregoing and / or the present invention may be implemented by a method of manufacturing an object by additive manufacturing. In one aspect, the method comprises (a) lowering a build platform having a given layer of build material to powder disposed on a window; (b) irradiating the powder to form a subsequent layer corresponding to the given layer; (c) curing the subsequent layer; (d) lifting the build platform and the cured subsequent layer away from the window; and (e) repeating steps (a)-(d) until the object is formed.

[0009] Aspects of the foregoing and / or the present invention may be implemented by an apparatus for additively manufacturing an object. In one aspect, the apparatus includes a powder dispenser, a window, and a platform on which the object is built. The apparatus also includes a recoater that provides a layer of powder to the window, and an irradiation source positioned below the window.

[0010] Technical Solution 1. A method for manufacturing an object by additive manufacturing, comprising: (a) lowering a build platform having a given layer of build material onto a powder disposed on a window; (b) irradiating the powder to form a subsequent layer corresponding to the given layer; (c) curing the subsequent layer; (d) lifting the build platform and cured subsequent layers away from the window; and (e) Repeating steps (a) to (d) until the object is formed.

[0011] Technical Solution 2. The method according to Technical Solution 1 is characterized in that the irradiation is digital light processing, laser or electron beam irradiation.

[0012] Technical Solution 3. The method according to Technical Solution 1 is characterized in that the powder has a melting point lower than the window.

[0013] Technical Solution 4. The method according to Technical Solution 1 is characterized in that the powder is irradiated through the window but adheres to a building platform positioned above the window.

[0014] Technical Solution 5. The method according to Technical Solution 1 is characterized in that the powder is a cobalt-chromium alloy, a stainless steel alloy, an aluminum alloy, a titanium alloy or a nickel-based super alloy.

[0015] Technical Solution 6. The method according to Technical Solution 1 is characterized in that the object is a turbine blade or a stator guide vane.

[0016] Technical Solution 7. The method according to Technical Solution 1 is characterized in that the object is the tip part of a turbine blade or a stator guide vane.

[0017] Technical Solution 8. A device for additive manufacturing of an object, comprising: Powder dispenser; window; a platform on which the object is constructed; a recoater that provides a layer of powder on the window; and An illumination source is positioned below the window.

[0018] Technical Solution 9. The device according to Technical Solution 8 is characterized in that the illumination source is a laser or a digital light projector.

[0019] Technical Solution 10. The device according to Technical Solution 8 is characterized in that the powder is irradiated through the window but adheres to the building plate above the window.

[0020] Technical Solution 11. The device according to Technical Solution 8 is characterized in that the powder has a melting point lower than the window.

[0021] Technical Solution 12. The equipment according to Technical Solution 8 is characterized in that the powder is cobalt-chromium alloy, stainless steel alloy, aluminum alloy, titanium alloy or nickel-based super alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A diagram of a conventional device for additive manufacturing.

[0023] Figure 2 An apparatus for additive manufacturing according to an embodiment of the present invention is shown.

[0024] Figure 3 An apparatus for additive manufacturing according to an embodiment of the present invention is shown.

[0025] Figure 4 An apparatus for additive manufacturing according to an embodiment of the present invention is shown.

[0026] Figure 5 An apparatus for additive manufacturing according to an embodiment of the present invention is shown.

[0027] Figure 6 is a diagram of an additive manufacturing process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The detailed description explained below in conjunction with the accompanying drawings is intended to be a description of various configurations and is not intended to represent the only configurations in which the concepts described herein can be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be clear to those skilled in the art that these concepts can be practiced without these specific details.

[0029] The present invention relates to additive manufacturing and uses, but is not limited to, additive techniques of metal powders in a layer-by-layer manner. In one aspect, the powdered metal can be melted to form each part layer. Those skilled in the art will recognize that the present invention is not limited to melting powders, but can also be applied to metal powders coated with polymers and slurries containing metal powders.

[0030] The present invention provides an apparatus capable of continuously extracting parts from loose powder or powder slurry by illuminating 2D sections from below the powder / slurry and continuously fusing the 2D sections until the part is completed and separated from the powder source.

[0031] Figure 2-5 An apparatus for additive manufacturing according to an exemplary embodiment of the present invention is shown. Figure 2 , the apparatus includes a build plate 200 oriented horizontally and configured to be lowered and raised vertically to build an object 202. Build plate 200 may be made of a heat resistant material that may be bonded to built object 202. For example, build plate 200 may be lowered to position built object 202 into metal powder 204.

[0032] The apparatus also includes a powder recoater mechanism 208 to provide a metal powder layer 204 onto the translucent window 206. The powder 204 may be supplied from a reservoir 210 by a powder feeder 212. The powder layer 204 may be thin or thick depending on the subsequent powder layer of the part being built. In general, the layer thickness may remain constant throughout the building process. Each time the object 202 is lifted from the powder 204, the recoater mechanism 208 moves horizontally and sweeps a uniform powder layer 204 onto the window 206. The recoater mechanism 208 may include a recoater blade (not shown) to provide control of the powder 204 on the window 206, and may also be configured as a hopper, for example, where the powder may fall onto the window 206.

[0033] Window 206 may define the length and width of the area for building object 202. The size of window 206 may vary depending on the size of the part being built. Window 206 may be made of a material that can withstand the energy emitted from the energy source. Window 206 may also be made of a material to which molten metal powder 204 may not be bonded. Exemplary materials for window 206 may include translucent materials (e.g., quartz and glass) that can withstand high heat. The melting point of metal powder 204 may be lower than the melting point of translucent window 206. However, in the case of high melting point metals, embodiments of the present invention may work by coating metal powder 204 with a radiation-curable polymer that fuses when exposed to a laser or other light source. Object 202 may then be further heat treated to drive off the polymer and / or fuse metal powder 204 into a solid object.

[0034] like Figure 2-5 As shown in , the apparatus may include an energy source 214 positioned below the translucent window 206. For example, the energy source 214 may be a laser or a laser galvanometer or a digital light projector capable of projecting light through the translucent window 206 and melting or fusing the metal powder 204 placed above the window 206. In the case where the energy source 214 is a digital light projector, for example, the energy source 214 is capable of projecting a 2D light pattern through the window 206.

[0035] like Figure 2 As shown in FIG. 2 , build plate 200 may be lowered so that the last layer of built object 202 contacts metal powder 204. Laser beam or light pattern 218 emitted from energy source 214 melts or fuses selected 2D regions of metal powder 204 (see FIG. 2 ). Figure 3 ). During re-solidification, Figure 4 As shown in , the fused layer forms the next layer 220 of the object 202. Figure 5 In the process, the build plate 200 can be raised and a new layer of powder 204 can then be provided on the translucent window 206 to continue building the object 202. This process can be repeated until the desired metal part is formed. As previously described, the new layer of powder can be thinner or thicker depending on the part being built, but the layer thickness is generally consistent throughout the process. Figure 2 As shown in , unused powder can be collected in container 216 for recycling and reuse.

[0036] For example, the metal powder material used to construct the object 202 may be stainless steel alloys, aluminum alloys, titanium alloys, nickel-based super metals, and cobalt-based super metals. In the case of using metal powder 204, the energy source 214 must be able to melt the powder 204 without destroying the translucent window 206. Low melting point powders or fusible alloys may be more suitable for use, and include, for example, known eutectic and non-eutectic alloys with melting points below 250°C.

[0037] Figure 62 is a diagram of an additive manufacturing process according to an embodiment of the present invention. For example, a first step may involve fastening a workpiece / object 202 to a build plate 200, and lowering the workpiece 202 onto a layer of metal powder 204. In step 2, the metal powder 204 may be irradiated via a window 206 that contacts the metal powder 204. The metal powder 204 may then melt into the workpiece 202 to form a new layer 220. In step 3, the workpiece 202 with the new layer 220 may then be lifted from the metal powder 204. In step 4, the new layer of metal powder 204 may be spread across the window 206. This process may be repeated until the desired part is fully built.

[0038] The above manufacturing method according to the exemplary embodiment can be used to repair the tip portion of a high-pressure turbine blade. U.S. Patent Application No. 15 / 439,643 filed by Garay et al. on February 22, 2017, "Method of Repairing a Turbine Component using Ultra-Thin Plate", discloses a method for repairing the tip of a turbine blade using metal powder additive technology. However, these methods require placing the turbine blade in a similar manner to Figure 1 The disadvantage of this approach is that the powder bed must be created at least around the part to be repaired or built.

[0039] The method according to an exemplary embodiment of the present invention is particularly advantageous for tip repairs because the turbine blade can be attached to the build platform and lowered toward the window so that only the portion of the tip to be repaired needs to come into contact with the metal powder. Thus, unnecessary powder usage can be eliminated. Using the present technique, for example, a damaged turbine blade tip can be ground to a flat surface, attached to the build plate so that the flat surface faces the window, and a portion of the turbine blade is lowered into the metal powder above the window where the build can occur. Furthermore, the above process according to the present exemplary embodiment can be used to produce an entire new turbine blade or stator vane, or other desired metal object.

[0040] This written description uses examples to disclose the present invention, including preferred embodiments, and also enables any person skilled in the art to practice the present invention, including making and using any device or system, and performing any incorporated method. The patent scope of the present invention is defined by the claims, and may include other examples that occur to those skilled in the art. If such other embodiments have structural elements that are not different from the written language of the claims, or if they include equivalent structural elements that are not substantially different from the written language of the claims, such other examples are expected to be within the scope of the claims. Aspects from the various embodiments described, as well as other known equivalents of each such aspect, can be mixed and matched by a person of ordinary skill in the art to constitute additional embodiments and techniques according to the principles of the present application.

Claims

1. A method of repairing a tip portion of a turbine blade or stator vane having a damaged tip by additive manufacturing, comprising: (a) attaching the turbine blade or the stator vane with the damaged tip ground to a flat surface to a build platform so that the flat surface faces downward; (b) lowering the build platform having the turbine blade or the stator vane with the damaged tip to position the planar surface of the damaged tip into powder provided on a window so that only the tip portion to be repaired contacts the powder, wherein the powder is a metal powder coated with a polymer; (c) irradiating the powder to form a layer onto the damaged tip; (d) curing the layer; (e) lifting the build platform and the cured layer away from the window; as well as (f) Repeating steps (b)-(e) until the damaged tip is repaired.

2. The method according to claim 1, wherein: The irradiation is digital light processing, laser or electron beam irradiation.

3. The method according to claim 1, wherein: The powder has a melting point below the window.

4. The method according to claim 1, wherein: The powder is irradiated through the window but adheres to the planar surface positioned above the window.

5. The method according to claim 1, wherein: The metal is a cobalt-chromium alloy, a stainless steel alloy, an aluminum alloy, a titanium alloy or a nickel-based super alloy.

6. An apparatus for additively repairing an object for performing the method according to claim 1, comprising: Powder dispenser; window; a platform, the object being secured to the platform, wherein the object includes a damaged tip ground to a flat surface and the platform is configured to hold the object such that the damaged tip faces downward; a recoater that provides a layer of powder on the window; as well as A radiation source is positioned below the window, wherein the apparatus is adapted to repair a distal end of the object.

7. The device according to claim 6, wherein: The illumination source is a laser or a digital light projector.

8. The device according to claim 6, wherein: The powder is irradiated through the window but adheres to the flat surface above the window.

9. The device according to claim 6, wherein: The powder has a melting point below the window.

10. The device according to claim 6, wherein: The metal is a cobalt-chromium alloy, a stainless steel alloy, an aluminum alloy, a titanium alloy or a nickel-based super alloy.

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