Patent Description:
Gas turbine engines generally include at least one compressor and at least one turbine section each having rotating blades contained within an engine housing. One of the goals in designing an engine housing is to maintain a lightweight structure while still providing enough strength to contain any rotating blade that may break (i.e. blade containment). Because any broken blades must be contained within the housing, the walls of engine housings must be manufactured to ensure broken blades do not puncture the housing.

Proposals to reduce weight, strengthen the turbine case, and/or to decrease the cost and increase efficiency of manufacturing have relied on additive manufacturing (AM) techniques. When an annular structure for use in a turbine is manufactured, AM may be utilized to form an annular and/or cylindrical component at a net shape or at a near net shape for further finishing. AM techniques are advantageous during the manufacturing process of annular components, and other components, in that AM techniques offer high geometric flexibility and when compared to subtractive manufacturing techniques or casting techniques and further may offer cost savings and flexibility in enabling changes to be made during the production process without retooling. However, components manufactured using AM techniques may not exhibit the desired properties of materials formed using more conventional manufacturing techniques (e.g. forging). Further, during the abovementioned example process, the additively manufactured component is generally formed on a disposable or sacrificial and/or reusable base substrate. After the component is complete, the base substrate is removed, as the sole purpose of the base substrate is to provide a base and/or support for forming the AM component. Background prior art is given in the following documents <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

The invention is defined by the subject-matter of the appended claims which are to be construed on basis of the description and drawings. Through the use of additive manufacturing techniques, an engine component may be formed on a base substrate, by employing the novel process to form a component discussed below, a component can be formed that incorporates the base material as part of the finished structure, thereby removing a manufacturing step from the process. Further, by employing the disclosed techniques, any one or combination of the advantages of: a reduction in material waste, a decrease in cost, and/or a decrease in manufacturing time are realized. The disclosed component and disclosed techniques further allow for components to be manufactured that utilize a hybrid structure, allowing the optimization of the structure of each portion of the component; accordingly, a component can be formed having the qualities of various materials and production processes at the locations of the component at which specific material qualities are desired. Additional advantages and novel features of these aspects will be set forth in part in the description that follows, and in part will become more apparent to those skilled in the art upon examination of the following or upon learning by practice of the disclosure.

Typically, turbine includes a compressor portion, a combustion portion, and a turbine portion. The turbine portion may include a gas generator turbine (GT) and a power turbine (PT). The majority of the description below describes an annular portion of an engine. Accordingly, the present invention may be applicable to any one of the turbine portions, the compressor portion or any other annular component of the turbine. The following detailed description sets a method of manufacturing an annular casing, and a produced annular engine casing as an example. The disclosed aspects may be implemented in the production of a high pressure turbine (HPT) or low pressure turbine (LPT), the high pressure compressor (HPC) or low pressure compressor (LPC), turbine center frame (TCF), and combustor, for example. The description should clearly enable one of ordinary skill in the art to make and use the manufacturing method and component, and the description sets forth several aspects, adaptations, variations, alternatives, and uses of the annular component, by way of example. The method of manufacturing the annular component described herein is applied to the construction of and resulting annular engine case.

The abovementioned annular component, according to the present invention, is manufactured using an additive manufacturing (AM) technique, which is a wire fed additive manufacturing process The above mentioned additive manufacturing techniques is used to form an engine casing or annular component from stainless steel, aluminum, titanium, Inconel <NUM>, Inconel <NUM>, Inconel <NUM>, cobalt chrome, among other metal materials or any alloy. For example, the above alloys may include materials with trade names, Haynes <NUM>®, Haynes <NUM>®, Super Alloy Inconel 625TM, Chronin® <NUM>, Altemp® <NUM>, Nickelvac® <NUM>, Nicrofer® <NUM>, Inconel <NUM>, and any other material having material properties attractive for the formation of annular components using the abovementioned techniques. AM processes generally involve the buildup of one or more materials to make a net or near net shape (NNS) object in contrast to subtractive manufacturing methods. Though "additive manufacturing" is an industry standard term (ASTM F2792), AM encompasses various manufacturing and prototyping techniques known under a variety of names, including freeform fabrication, 3D printing, rapid prototyping/tooling, etc. AM techniques are capable of fabricating complex components from a wide variety of materials. Generally, a freestanding object can be fabricated from a computer aided design (CAD) model. As an example, a particular type of AM process uses an energy beam, for example, an electron beam or electromagnetic radiation such as a laser beam, to sinter or melt a powder material and/or wire-stock, creating a solid three-dimensional object in which a material is bonded together.

Selective laser sintering, direct laser sintering, selective laser melting, and direct laser melting are common industry terms used to refer to producing three-dimensional (3D) objects by using a laser beam to sinter or melt a fine powder. For example, <CIT> and <CIT> describe conventional laser sintering techniques. More accurately, sintering entails fusing (agglomerating) particles of a powder at a temperature below the melting point of the powder material, whereas melting entails fully melting particles of a powder to form a solid homogeneous mass. The physical processes associated with laser sintering or laser melting include heat transfer to a powder material and then either sintering or melting the powder material. In general, the abovementioned processes are performed on build platform, which may be a reusable or sacrificial substrate. In the above-mentioned processes, conventionally, the build platform is removed from the component formed after a component build is complete.

<FIG> is a schematic diagram showing an exemplary conventional wire fed AM apparatus and method. The apparatus may be configured to build objects, for example, a part <NUM>, in a layer-by-layer manner by feeding wire-stock <NUM>, fed by a wire feed apparatus <NUM>, and sintering and/or melting the wire using an energy source <NUM>, which may be, for example, an electron beam or electromagnetic radiation such as a laser beam. The building of the part <NUM>, may be on a substrate <NUM>. The energy source <NUM> may form a melt pool <NUM>, which solidifies to form at least a portion of the part <NUM>. Either the wire fed AM apparatus, the substrate, or both may be lowered and/or moved, while melting the wire-stock on any portion of the substrate <NUM> and/or on the previously solidified part <NUM> until the part is completely built up from a plurality of beads formed from the melted wire-stock. The energy source <NUM>, may be controlled by a computer system including a processor and a memory. The computer system may determine a predetermined path for each melt pool and subsequently solidified bead to be formed, and energy source <NUM> to irradiate the wire material according to a pre-programmed path. After fabrication of the part <NUM> is complete, various post-processing procedures may be applied to the part <NUM>. Post processing procedures include removal of excess melted wire-stock material, for example, by machining, sanding or media blasting. In the past, conventional post processing also involved removal of the part <NUM> from the build platform/substrate <NUM> through machining, for example. Other post processing procedures may include a stress release process, thermal and/or chemical post processing procedures to finish the part <NUM>. As further examples, <CIT> and <CIT> describe conventional wire fed AM processes.

<FIG> is a schematic diagram showing another exemplary conventional powder based system for building an AM component. The apparatus <NUM>, is used to build components, for example, a part formed using stacked layers <NUM>, by sintering or melting a powder material <NUM> fed though a nozzle by a powder feed source <NUM>. The powder <NUM> is fed along with shield gas <NUM> though a shield gas source <NUM>. As the powder is fed, the powder is melted into a melt pool <NUM> and/or sintered by an energy source <NUM>. The energy source <NUM>, may be provided, for example, as an electron beam or as electromagnetic radiation such as a laser beam. The building of the part <NUM>, may be on a substrate <NUM>. The melt pool <NUM>, formed when the energy source melts and/or sinters the powder <NUM>, solidifies to form at least a portion of the part <NUM>. Either the powder fed AM apparatus, the substrate, or both may be lowered and/or moved, to melt the wire on any portion of the substrate <NUM> and/or on the previously solidified part <NUM> until the part is completely built up from a plurality deposited layers <NUM> built from melted powder <NUM>. The energy source <NUM>, may be controlled by a computer system including a processor and a memory. The computer system may determine a predetermined path for each melt pool and subsequently solidified bead to be formed, and energy source <NUM> to irradiate the powder material according to a pre-programmed path. After fabrication of the part <NUM> is complete, various post-processing procedures may be applied to the part <NUM>. Post processing procedures include removal of excess powder, for example, by blowing or vacuuming, machining, sanding or media blasting. Further, conventional post processing may involve removal of the part <NUM> from the build platform/substrate <NUM> through machining, for example. The part may further be subject to a stress release process. Additionally, thermal and chemical post processing procedures can be used to finish the part <NUM>.

<FIG> is schematic diagram showing a cross-sectional view of an exemplary conventional system <NUM> for direct metal laser sintering (DMLS) or direct metal laser melting (DMLM). The apparatus <NUM> builds objects, for example, the part <NUM>, in a layer-by-layer manner by sintering or melting a powder material (not shown) using an energy beam <NUM> generated by a source such as a laser <NUM>. The powder to be melted by the energy beam is supplied by reservoir <NUM> and spread evenly over a build plate <NUM> using a recoater arm <NUM> travelling in direction <NUM> to maintain the powder at a level <NUM> and remove excess powder material extending above the powder level <NUM> to waste container <NUM>. The energy beam <NUM> sinters or melts a cross sectional layer of the object being built under control of the galvo scanner <NUM>. The build plate <NUM> is lowered and another layer of powder is spread over the build plate and object being built, followed by successive melting/sintering of the powder by the laser <NUM>. The process is repeated until the part <NUM> is completely built up from the melted/sintered powder material. The laser <NUM> may be controlled by a computer system including a processor and a memory. The computer system may determine a scan pattern for each layer and control laser <NUM> to irradiate the powder material according to the scan pattern. After fabrication of the part <NUM> is complete, various post-processing procedures may be applied to the part <NUM>. Post processing procedures include removal of excess powder, for example, by blowing or vacuuming, machining, sanding or media blasting. Further, conventional post processing may involve removal of the part <NUM> from the build platform/substrate through machining, for example. Other post processing procedures include a stress release process. Additionally, thermal and chemical post processing procedures can be used to finish the part <NUM>.

Any of the abovementioned AM processes may be controlled by a computer executing a control program. For example, the apparatus <NUM> includes a processor (e.g., a microprocessor) executing firmware, an operating system, or other software that provides an interface between the apparatus <NUM> and an operator. The computer receives, as input, a three dimensional model of the object to be formed. For example, the three dimensional model is generated using a computer aided design (CAD) program. The computer analyzes the model and proposes a tool path for each object within the model. The operator may define or adjust various parameters of the scan pattern such as power, speed, and spacing, but generally does not program the tool path directly. One having ordinary skill in the art would fully appreciate the abovementioned control program may be applicable to any of the abovementioned AM processes. Further, the abovementioned computer control may be applicable to any subtractive manufacturing or any pre or post processing techniques employed in any post processing or hybrid process.

The flowchart in <FIG> depicts one aspect of the present invention. Reference <NUM> involves the selection or forming of a base substrate (an example of which is shown in <FIG>). The base substrate may be formed of any suitable material. The base substrate <NUM>, may be supplied as a raw material or may have any preparatory process applied. For example, the material may be sanded, media blasted, and/or may be prepared by machining, forging, and/or annealing. Further the base substrate may be chemically treated. The base substrate is further provided as a supplied forged substrate, and may be machined either before and/or after the below mentioned AM process is applied. For example, as shown in <FIG>, the base substrate may be machined into a round base and may have at least a single machined step portion <NUM> for either clamping to a worksurface <NUM> or for forming a section of the desired geometry of the finished product. Further, the base substrate may be provided with an annular raised portion and/or a channel (not shown) which may correspond with the portion of the substrate at which an AM build is to be applied. The base portion <NUM> may further be drilled either to assist in mounting the substrate <NUM> to the base <NUM> and/or may be drilled for holes required on the finished part. The substrate <NUM> may further be machined or provided as a ring having a center opening (as shown in <FIG>).

The base portion <NUM> may be pre-formed as a flange having any desired mounting holes, provisions, or portions to allow for sealing or mating of the flange with desired mating surfaces when completed component is assembled. The flange and/or base substrate <NUM> may be a material having optimal characteristics for the finished geometry associated with the base portion. For example, a flange portion may require the mechanical and material characteristics of a forged material (e.g. improved elongation, yield strength, ultimate tensile strength). Further the flange may subject to any processing to optimize the mechanical characteristics for use (e.g. hot working, cold working, annealing, and/or hardening). As shown in FIGs 11A and 11B, the base <NUM> substrate may be sourced or machined prior to an AM build to have at least one hole <NUM>, and may be machined or forged to have a step portion <NUM>. The base <NUM>, may be selected and prepared in anticipation of a final machining of a flange portion <NUM>.

As shown in reference <NUM> of <FIG>, an AM technique may be applied to the substrate. According to the present invention the above mentioned laser wire AM process is applied to the base substrate to build the annular portion of the component. As shown in the example component depicted in <FIG>, the abovementioned AM process is used to form an annular portion of the component <NUM> on the base substrate <NUM>. The annular portion of the component is formed layer by layer, either by rotation of the AM apparatus <NUM> and/or a rotation of the base portion <NUM>. Further the base portion <NUM> and/or the AM apparatus <NUM> may be angled during the build process to form a second flange <NUM>, an example of the second flange is shown in <FIG> and <NUM>. The annular portion, is not limited to, and may be formed of any of the abovementioned materials and formed using the above mentioned AM process An AM process is selected based on the desired cost, accuracy, repeatability, resolution, stability and/or mechanical properties of the build, and/or a desired build rate. When forming a large component having an annular structure, the above mentioned laser wire AM process provides the benefit of a faster and more efficient build at the expense of resolution and accuracy. The annular portion of the component formed using an AM process may exhibit material properties (e.g. yield strength, ultimate tensile strength, elongation) between a cast and a forged material, which may be desirable in terms of stresses the annular component is subjected to and/or the cost effectiveness of the completed component. The forged base portion <NUM>, may be preferable as a flange, as a forged material may exhibit higher yield strength, higher ultimate tensile strength, elongation, and reduced porosity and/or cavities and voids throughout the material than the annular portion <NUM> formed using an AM process. Accordingly, by providing the base portion <NUM> as a portion of the finished component the advantages of both a forged material for the flange and an annular structure formed using an AM process may be realized, as one example.

Based on the above mentioned example, the yield strength at <NUM> of the annular portion <NUM>, represented by variable C, formed of the same material as the forged base material represented by variable X satisfies the following equation: <MAT> Further, according to the present invention, the ultimate tensile strength at <NUM> of the annular portion <NUM>, represented by variable Y, formed of the same material as the forged base material represented by variable G satisfies the following equation: <MAT> Elongation at <NUM> of the annular portion <NUM>, represented by variable T, formed of the same material as the forged base material represented by variable F satisfies the following equation: <MAT>.

As shown in <FIG>, <FIG>, and <FIG>, once a net shape AM process is performed on the base <NUM>, <NUM>, <NUM>, the surface of the built AM portion of the component and/or the base may be subject to a stress relief and/or heat treatment process (<FIG>, reference <NUM>). Step <NUM> may include, annealing, stress relief annealing, thermal treatment, shot peening, vibratory stress relief, tempering, quenching, and/or any chemical process may be applied to the build. As shown in <FIG>, step <NUM>, the outer and/or inner annular structure may further be machined to remove any excess material imparted during the AM build process. The flange or base portion <NUM>, <NUM>, <NUM> may further be machined either before and/or after or during the machining of the annular AM portion <NUM> of the component.

Claim 1:
An annular turbine engine component, comprising:
a forged base formed of a forged material having a yield strength at <NUM> represented by X;
a metallic conical portion formed by a wire fed additive manufacturing process and joined with the forged base, the metallic conical portion formed of a material having a yield strength at <NUM> represented by C, wherein the equation C ≤ <NUM>.87X is satisfied, wherein the metallic conical portion (<NUM>) is formed of the same material as the forged base (<NUM>);
wherein the annular turbine engine component is an annular engine case;
wherein the metallic conical portion has at least one boss formed on a surface via a powder-based AM process, the at least one boss having an outer flange (<NUM>), an inner flange (<NUM>), and an annular step portion (<NUM>) extending outwardly from the surface;
wherein the forged base has an ultimate tensile strength at <NUM> represented by G, and the metallic conical portion has an ultimate tensile strength at <NUM> represented by Y, wherein the equation Y ≤ <NUM> is satisfied; and
wherein the forged base has an elongation at <NUM> represented by F, and the metallic conical portion has an elongation at <NUM> represented by T, wherein the equation T ≤ <NUM>.82F is satisfied.