Patent Application
20200238376
The present disclosure generally relates to methods of manufacturing components using metal alloys. More particularly, the present disclosure relates to additively manufactured turbine components with aluminum-iron-vanadium-silicon alloys utilizing a powder coating process.
In the context of gas turbine engines, the need for lighter weight components and higher gas turbine engine operating temperatures has created a need for aluminum to replace steels and titanium in the 250° F. to 600° F. mid-temperature operating range. Aluminum-iron-vanadium-silicon alloys, such as aluminum alloy 8009 (Al-8009), have been shown to be capable of operating at up to 600° F. and able to withstand excursions up to 800° F. Accordingly, Al-8009 and similar alloys could be substituted for titanium in the main and trim bleed valves in gas turbine engines, which would result in a considerable cost and weight reduction.
Accordingly, it is desirable to provide improved methods for manufacturing components from Al—Fe—V—Si alloys. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings.
According to various embodiments, disclosed is a method for manufacturing an article, including: providing a three-dimensional computer model of the article; providing a Al—Fe—V—Si metal alloy in powdered form comprising a plurality of powder particles; coating the plurality of powder particles with a coating of silicon using a chemical vapor deposition process; at a powder bed additive manufacturing apparatus, supplying the coated metal alloy and loading the three-dimensional model; and using the powder bed additive manufacturing apparatus, manufacturing the article in accordance with the loaded three-dimensional model in a layer-by-layer manner with the supplied coated metal alloy.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
The exemplary embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
The following detailed description is merely exemplary in nature and is not intended to limit the inventive subject matter or the application and uses of the inventive subject matter. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.
Al—Fe—V—Si alloy components require a multi-step process that includes rapid solidification ribbon casting, ribbon pulverizing, powder canning, hot isostatic pressing (HIP), extrusion, and forging to generate and maintain its unique microstructure and material properties. It has been found that the need for extensive hot working by extrusion and forging also limits the size and complexity of parts that can be practicably produced from the alloy.
It has been observed that melt spinning has been the only practical means of producing solidification cooling rates high enough, ˜106° F./second, to form the desired microstructure in this material. Melt spinning processes produce thin (˜0.001″) alloy ribbons by impinging a molten metal stream onto a rapidly spinning, water cooled wheel, as illustrated in
When the Al—Fe—V—Si alloy is melt spun, the rapid solidification produces enhanced solubility of iron, vanadium, and silicon, and allows for the formation of a very fine dispersion of Al(Fe,V) silicides, which is a very effective strengthening mechanism. However, it has been observed that the production of useful components from the rapidly solidified ribbons or flakes involves a series of manufacturing process steps that are time consuming and expensive (see
In order to avoid these steps, one prior art approach uses additive manufacturing processes, such as direct metal laser sintering (DMLS) or electron beam melting (EBM), which can be used to produce components directly from atomized Al—Fe—V—Si alloy powder. The DMLS process may allow for the elimination of several expensive manufacturing processes associated with producing parts from MS ribbons, in addition to having more design freedom. The rapid cooling of the Al—Fe—V—Si alloy via the DMLS process has been thought to allow for the manufacturing of components directly from the alloy powder material, built up by using a scanning laser to melt and solidify very thin (less than 0.001″) layers of powder. The cooling rates achieved by utilizing this technology are as high as 107° F./second (depending upon build geometry, laser focal parameters, laser power and laser scanning speed), thus in theory producing the desired microstructure directly in the part without the costs and complexities of the MCS processing. However, in some scenarios, has been found that using DMSL technology in this context introduces remelting of the previously atomized powder and thus puts the optimal rapidly solidified microstructure at theoretical risk of non-uniform solidification rates based on part cross section geometry. In order to avoid the aforesaid remelting that may occur when using DMLS, the present disclosure utilizes a novel powder coating process before loading the powder into the DMLS machine, as will be described in greater detail below.
Exemplary methods for manufacturing an article include providing a metal alloy in powdered form. The metal alloy is an aluminum-iron-vanadium-silicon alloy. Al—Fe—V—Si alloys contain a uniform dispersion of stable (up to about 350° C.), nanometer scale silicides with a composition of about Al12(Fe,V)3Si in an aluminum solid solution matrix. Al—Fe—V—Si alloys have been developed that have mechanical properties comparable to titanium alloys up to temperatures of around 350° C. and can, because of their lower density —2.9 compared to 4.5 g/cm3 —result in significant weight savings in several gas turbine engine applications.
Alloys suitable for use in the process of the present disclosure are the rapidly solidified high-temperature aluminum alloys disclosed in U.S. Pat. Nos. 4,729,790, 4,828,632, and 4,878,967. Such alloys have a composition of the formula AlbalFeaSibXc, wherein X is at least one element selected from the group consisting of Mn, V, Cr, Mo, W, Nb, Ta; “a” ranges from 2.0 to 7.5 at % (atomic percent); “b” ranges from 0.5 to 3.0 at %; “c” ranges from 0.05 to 3.5 at %, and the balance is aluminum plus incidental impurities, with the proviso that the ratio [Fe+X]:Si is within the range from about 2.0:1 to 5.0:1.
The alloys used in this disclosure are preferably based on Al—Fe—V—Si. The Al—Fe—V—Si alloy in accordance with the present disclosure may be the Al-8009 alloy. Accordingly, Al—Fe—V—Si alloys that may be used in accordance with the present disclosure may be characterized by the following composition (TABLE 1), in weight-%:
Al—Fe—V—Si alloys in accordance with other embodiments of the present disclosure may be characterized by the following composition (TABLE 2), in weight-%:
The powdered form of the Al—Fe—V—Si alloy is produced by combining the various constituents (metals and other elements) of the alloy into a mixture, melting the mixture, and atomizing the melted mixture to form a powder, a process which is well-known in the art. The atomization process is performed due to the fact that it is capable of producing substantially spherical grains of the powder—as is well-known in the art, due to the nature of AM processes when the powder is “swept” onto the bed in thin layers, it is desirable to have particles that are as spherical as possible for consistency in the thickness of the new layer on the bed. The powdered form suitable for use in accordance with embodiments of the present disclosure may be characterized by a grain size range of about 5 to about 22 microns and a d50 grain size average of about 10 to about 13 microns, such as a grain size of about 10 to about 17 microns and a d50 grain size average of about 11 to about 12 microns. (As is conventional in the art, sizes herein are measure assuming spherical grains.) Powders that are characterized by this relatively small in grain size enable finer detail in the finished printed component. A powder coating process is also employed, as will be described in greater detail below, subsequent to making the powder as described herein. The powder coating process will be described after the following powder-bad additive manufacturing process description.
Using a novel powder-bed additive manufacturing (PBAM) approach (such as DMLS), it is now possible to create a manufacturing process to produce near-net shape components directly from ceramic strengthened powders that, until now, could only be produced using the prior art more expensive methods. PBAM is a manufacturing process that allows for the manufacturing of components layer-by-layer. The PBAM process allows for the elimination of expensive manufacturing processes associated with producing parts from press and sinter methods. The laser melting and subsequent rapid cooling of alloy powders to produce an alloy via PBAM is a unique process to produce components even with intricate internal passages that are not possible using the prior art technologies. PBAM enables the manufacturing of components directly from pre-alloyed powders built by using a scanning laser to melt and solidify very thin (less than 0.001″) layers of powder. The cooling rates achieved by utilizing this technology are as high as 107° F./second (depending upon build geometry, laser focal parameters, laser power and laser scanning speed) thus producing the desired microstructure directly in the part without the costs and complexities of prior art processing steps.
Greater detail is now provided regarding the powder bed additive manufacturing techniques that may be used in connection with the above-described pre-alloy powders, and that achieve the aforementioned essential features of the present disclosure. Suitable powder bed additive manufacturing processes use a small, focused beam to build a component by fusing one layer of powder to the layer of powder directly beneath it, thus using the underlying previously solidified layers as a heat sink to achieve high cooling rates in the currently deposited and melted layer. The heat input for the process is controlled with laser focal parameters, laser power, and laser scanning speed. The rapid solidification rate is controlled by the conduction from the currently melted layer to the underlying previously solidified layers. Thus, powder bed temperature, support structures, and PBAM build foundation are all designed and controlled to provide the necessary heat sink parameters to achieve the appropriate microstructure. The PBAM process enables parts to be formed to near-net where appropriate, which eliminates expensive machining costs associated with prior art processes.
In step 220 of the method 200, the component is formed according to the model of step 210. In one exemplary embodiment, a portion of the component is formed using a rapid prototyping or additive layer manufacturing process. In other embodiments, the entire component is formed using a rapid prototyping or additive layer manufacturing process. Although additive layer manufacturing processes are described in greater detail below, in still other alternative embodiments, portions of the component may be forged or cast in step 220.
Some examples of additive layer manufacturing processes include: selective laser sintering in which a laser is used to sinter a powder media in precisely controlled locations; laser wire deposition in which a wire feedstock is melted by a laser and then deposited and solidified in precise locations to build the product; electron beam melting; laser engineered net shaping; and selective laser melting. In general, powder bed additive manufacturing techniques provide flexibility in free-form fabrication without geometric constraints, fast material processing time, and innovative joining techniques. In one particular exemplary embodiment, PBAM is used to produce the component in step 220. PBAM is a commercially available laser-based rapid prototyping and tooling process by which complex parts may be directly produced by precision melting and solidification of metal powder into successive layers of larger structures, each layer corresponding to a cross-sectional layer of the 3D component.
As such, in one exemplary embodiment, step 220 is performed with PBAM techniques to form the component. However, prior to a discussion of the subsequent method steps, reference is made to
Referring to
During operation, a base block 340 may be installed on the fabrication support 314. The fabrication support 314 is lowered and the delivery support 334 is raised. The roller or wiper 336 scrapes or otherwise pushes a portion of the coated-powder build material 370 from the delivery device 330 to form the working plane 316 in the fabrication device 310. The laser 360 emits a laser beam 362, which is directed by the scanner 320 onto the build material 370 in the working plane 316 to selectively fuse the build material 370 into a cross-sectional layer of the article 350 according to the design. More specifically, the speed, position, and other operating parameters of the laser beam 362 are controlled to selectively fuse the coated-powder of the build material 370 into larger structures by rapidly melting the powder particles that may melt or diffuse into the solid structure below, and subsequently, cool and re-solidify. As such, based on the control of the laser beam 362, each layer of build material 370 may include unfused and fused build material 370 that respectively corresponds to the cross-sectional passages and walls that form the article 350. In general, the laser beam 362 is relatively low power to selectively fuse the individual layer of build material 370. As an example, the laser beam 362 may have a power of approximately 50 to 500 Watts, although any suitable power may be provided.
Upon completion of a respective layer, the fabrication support 314 is lowered and the delivery support 334 is raised. Typically, the fabrication support 314, and thus the article 350, does not move in a horizontal plane during this step. The roller or wiper 336 again pushes a portion of the coated-powder build material 370 from the delivery device 330 to form an additional layer of build material 370 on the working plane 316 of the fabrication device 310. The laser beam 362 is movably supported relative to the article 350 and is again controlled to selectively form another cross-sectional layer. As such, the article 350 is positioned in a bed of build material 370 as the successive layers are formed such that the unfused and fused material supports subsequent layers. This process is continued according to the modeled design as successive cross-sectional layers are formed into the completed desired portion, e.g., the component of step 220.
The delivery of coated-powder build material 370 and movement of the article 350 in the vertical direction are relatively constant and only the movement of the laser beam 362 is selectively controlled to provide a simpler and more precise implementation. The localized fusing of the build material 370 enables more precise placement of fused material to reduce or eliminate the occurrence of over-deposition of material and excessive energy or heat, which may otherwise result in cracking or distortion. The unused and unfused build material 370 may be reused, thereby further reducing scrap.
Any suitable laser and laser parameters may be used, including considerations with respect to power, laser beam spot size, and scanning velocity. The build material 370 is provided as an Al—Fe—V—Si alloy in a pre-alloy coated-powder form, as described below. In general, the coated-powder build material 370 may be selected for enhanced strength, durability, and useful life, particularly at high temperatures, although as described below, the powder build material 370 may also be selected based on the intended function of the area being formed. The coated-powder form of the alloy is produced by combining the various constituents (metals and other elements) of the alloy into a mixture, melting the mixture, and atomizing the melted mixture to form a powder, a process which is well-known in the art, and thereafter coating using chemical vapor deposition, as will be described below.
Returning to
Great potential exists for powder bed additive Manufacturing (PBAM) to produce components using alloys that have a high predictability to cracking due to the chemistry of the powder. To prevent the procurement of an expensive heat of material that would later be forged into wire or bar for atomization, chemical vapor deposition (CVD) can be used to encapsulate the Al—Fe—V—Si material with a more weld friendly alloy. CVD is a process that has the advantage of forming a new alloy mixture by coating powder after it (the powder) has been atomization.
The present disclosure overcomes the deficiencies in the prior art by introducing a process that coats the Al—Fe—V—Si powder in silicon. This addition increases the silicon content to approximately 2.5 wt % (such as about 2.2% to about 2.8%, about 2.3% to about 2.7%, or about 2.4% to about 2.6%), providing a solidification range and improving fluidity, increasing the weldability of the alloy.
In CVD, the base powder is exposed to one or more volatile precursors, which react and/or decompose on the powder surface to produce the desired deposit. Volatile by-products are also produced, which are removed by gas flow through the reaction chamber. Silicon may be deposited using precursors such as trichlorosilane or silane.
Accordingly, the present disclosure has provided methods that utilize CVD to coat Al—Fe—V—Si powder particles with a coating of silicon, prior to being used in an additive manufacturing process to manufacture an article, such as a turbine engine component. Furthermore, the present disclosure has provided methods that enable parts to be formed closer to near-net where appropriate, which eliminates expensive machining costs associated with prior art post-build processes.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.
The present application claims the benefit of priority to U.S. provisional patent application 62/798,640, which was filed on Jan. 30, 2019, the contents of which are hereby incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62798640 | Jan 2019 | US |
