Patent Application
20210078107
The present disclosure is generally directed to additive manufacturing, and more particularly, to reactive additive manufacturing of ceramic-metal powder mixtures to provide three-dimensional (3D) metallic matrix composite articles having improved properties such as strength properties, corrosion resistant/inhibiting properties, hardness properties, and the like throughout the bulk (e.g., the three-dimensional volume) of the article.
Metallic matrix composites (MMC) are composite materials including at least two constituent components with one component being a metal and the other component being a ceramic or an organic compound or an intermetallic. When properly designed, MMCs meld the best physical properties of metals (high ductility, work hardening rates, and conductivity) with those of ceramics (high stiffness, strength, and low density). These property combinations can yield materials that operate in regions of Gibson-Ashby charts (e.g., high specific strength and conductivity) that are unattainable with conventional metallic or ceramic materials alone. However, despite their disruptive potential, the major impediment to their widespread use is synthesis and processing.
It is exceedingly difficult to use traditional manufacturing methods to synthesize MMCs at any fabrication stage: uniformly dispersing a ceramic phase into a molten metal matrix (e.g., stir casting) is notoriously challenging and becomes worse with increasing ceramic volume fraction; metal/ceramic interfaces tend to be incoherent and weak unless carefully grown via physical vapor deposition; and it is near-impossible to post-process machine and thermo-mechanically work MMCs because metals and ceramics have such disparate properties. Because of these significant impediments, three-dimensional structures formed of MMCs have been very slow to be adopted because they are difficult to reproducibly manufacture especially with structures exhibiting complex geometries. Current processes typically need specially designed molds, carefully controlled heat treatments, and cannot produce three dimensional articles having complex geometries.
Disclosed herein are additive manufacturing processes and metal-ceramic composites. In one or more embodiments, an additive manufacturing process for producing a three-dimensional article includes providing a layer of feedstock including a plurality of metallic particles of one or more metals and a plurality of ceramic particles of one or more ceramic materials. The layer of the feedstock is exposed to an energy beam in a pattern to form a metal-ceramic composite in the pattern, wherein forming the metal-ceramic composite includes tailoring optical properties of the feedstock in different areas within the layer to change energy absorption of the energy beam by the feedstock in the different areas. At least one additional layer of the feedstock is deposited and the exposing is repeated on the at least one additional layer to form the three-dimensional article.
In one or more embodiments, the additive manufacturing process for producing a three-dimensional article includes providing a layer of feedstock including a plurality of metallic particles of one or more metals and a plurality of ceramic particles of one or more ceramic materials. The layer of the feedstock is exposed to an energy beam in a pattern to form a metal-ceramic composite in the pattern, wherein forming the metal-ceramic composite includes tailoring heat flow in different areas of the layer by changing thermal conductivity of the ceramic particles therein to enable an increase or a decrease in a cooling rate in the different areas. At least one additional layer of the feedstock is deposited and the exposing is repeated on the at least one additional layer to form the three-dimensional article.
A metal-ceramic matrix composite includes a metal, a ceramic, and a reaction zone between the metal and a ceramic particle, wherein the reaction zone comprises nitrides, borides, carbides, oxides, silicides or combinations thereof of the metal having a different composition than the ceramic.
Additional features and advantages are realized through the techniques of the embodiments of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the embodiments of the invention with advantages and features, refer to the description and to the drawings.
Example embodiments of the invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout, and wherein:
The present disclosure is generally directed to reactive additive manufacturing (AM) processes for forming three-dimensional structures of metallic matrix composites (MMCs). In one or more embodiments, the MMC three-dimensional structures are formed from a powder bed including metal particles and ceramic particles or from a wire feedstock including one or more metals and one or more ceramics. More particularly, the reactive additive manufacturing process includes a selective energy beam melting AM process using a laser energy beam or E-beam for sequentially forming the three-dimensional structure layer-by-layer. Unlike the use of dies or molds for producing relatively simple shapes, it has been discovered that AM processes of the present disclosure can be used to directly synthesize MMCs into complex geometries, which removes many of the limitations hindering adoption of these materials. Moreover, as will be described in greater detail herein. AM processing using selective energy beam synthesis of powder beds including metal particles and ceramic particles or wire feedstocks including one or more metals and one or more ceramics can be used to provide unique MMC structures that are only possible with AM. In conventional solid-state manufacture of MMCs, a blend of the metal and the ceramic are typically diffusion bonded in a particular arrangement and then pressed at an elevated temperature or sintered in which a powder of a matrix metal is mixed with a powder of the dispersed phase and heated at a temperature close to the melting point of the metal. In contrast, the AM process of the present disclosure can be used to provide reactive zones between a matrix metal and a dispersed ceramic phase.
In the AM process of the present disclosure, the ceramic particles can be dispersed in the metal powder matrix (or metal from wire feedstock in the event a wire process is utilized) and selected to increase energy transfer during the AM process. The presence of the ceramic particles during the AM process changes the optical properties and/or the thermal conductivity of the powder bed since the ceramic particles can be provided to have markedly different optical properties and/or thermal conductivities relative to metal particles. Likewise, the presence of the ceramic during melting of the wires can increase energy transfer during the AM process. Applicants have found that one or both of these properties can be tailored in different areas within a given layer to change energy absorption of the energy beam in the different areas. In this manner, ceramic reinforcement into metallic builds through reactive chemistry can produce MMCs or gradient materials that include MMCs that exhibit significantly improved performance characteristics of the three-dimensional structure including, but not limited to, increases in yield strength and tensile strength at room temperature and above while maintaining ductility, increases in creep resistance at higher temperatures compared to conventional alloys, increases in fatigue strength, improvement of thermal shock resistance, improvement of corrosion resistance, increases in Young's modulus, and reduction of thermal elongation, among other characteristics.
For convenience in understanding the present disclosure, reference will be made to powder bed feedstocks. However, it should be noted that the AM processes of wire feedstocks and the resulting benefits described herein for producing MMC metal builds is equally applicable. The optical properties of the ceramic particles can be selected to be reflective or absorbent of the input energy depending on the ceramic composition resulting in endothermic solidification or exothermic solidification or a combination of exothermic and endothermic solidification upon cooling. For endothermic reactions, limited local propagation of the reaction in adjacent areas may occur. For exothermic reactions, the heat will be conducted to adjacent regions and can propagate the reaction in these adjacent areas. By way of example, tungsten oxide ceramic particles having different oxidation states can be used in metal builds to manipulate laser energy absorption in different areas of the layer depending on the oxidation state to produce a different crystalline structures in selected areas of the metal build during the AM process. The different oxidation states provide different amounts of laser energy absorption based on the oxidation state. Advantageously, the presence of the ceramic particles in the powder bed can result in decreased amounts of laser energy (or E-beam) needed during the AM process to form the three-dimensional structure.
In a similar manner, the ceramic particles can provide a thermal conductivity that can be used to provide different crystalline structures within the composite. The ceramic particles can be selected to function as a heat sink or as a heat source to control the energy release into the metal matrix. As such, the thermal conductivity of the ceramic particles can be selected to have a greater or lesser thermal conductivity than the metal particles. As an example, a conventional metal powder bed used during selective laser metal AM manufacturing is prone to pore formation. In contrast, the ceramic particles dispersed throughout the metal powder bed can be selected to provide heat release during the selective laser melting AM process, which can prevent or minimize pore formation during solidification.
Conventional techniques related to AM processes for forming three-dimensional articles may or may not be described in detail herein. Moreover, the various tasks and process steps described herein can be incorporated into a more comprehensive procedure or process having additional steps or functionality not described in detail herein. In particular, various steps in the additive manufacture of three-dimensional articles are well known and so, in the interest of brevity, many conventional steps will only be mentioned briefly herein or will be omitted entirely without providing the well-known process details.
As used herein, the term “ceramic particles” refers to a solid material including an inorganic compound of a metal or metalloid and a non-metal with ionic or covalent bonds generally based on an oxide, nitride, boride or carbide. In one or more embodiments, the ceramic particles can range in size from about 0.01 μm to about 1000 μm; in one or more other embodiments, the ceramic particles can range in size from about 0.1 μm to about 500 μm; and in still one or more other embodiment, the ceramic particles can range in size from about 1.0 μm to about 100 μm. Non-limiting examples of ceramics include oxides, nitrides, borides, and carbides such as semi-metal elements such as B, Si, Ge, Sb, and Bi, Mg, Ca, Sr, Ba, Zn, Al, Ga, In, Sn, and Pb; transition metal elements such as Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag, and Au; and lanthanides such as La, Ce, Pr, Nd, Sm, Er, Lu.
The term “metal particles” generally refers to particles of an individual metal that can be selective laser melt AM processed. In one or more embodiments, the metal particles can range in size from about 1 μm to about 5000 μm; in one or more other embodiments, the ceramic particles can range in size from about 5 μm to about 1000 μm; and in still one or more other embodiment, the ceramic particles can range in size from about 10 μm to about 300 μm. The particular metal is not intended to be limited and can be an alkali metal, alkaline earth metal, transition metal, a rare earth metal or combination thereof. Non-limiting examples of metallic materials include aluminum and its alloys, titanium and its alloys, nickel and its alloys, chromium-based alloys, stainless or chrome steels, copper alloys, cobalt-chrome alloys, tantalum, niobium, iron-based alloys, combinations thereof, and the like.
The one or more metals define a metal matrix and have a larger volume ratio relative to the volume of the ceramic particles. In one or more embodiments, the volume percentage of the ceramic particles in the powder is greater than about 0 to about 80%; in one or more other embodiments, the volume percentage of the ceramic particles is from about 0.5% to about 40%; and in still one or more other embodiments, the ceramic particles can range in size from about 2% to about 30%, wherein the volume percentage is based on the total volume of the metal and ceramic particles. The upper limits generally depend on the composition and intended application.
For the purposes of the description hereinafter, the terms “upper”, “lower”, “top”, “bottom”, “left,” and “right,” and derivatives thereof shall relate to the described structures, as they are oriented in the drawing figures. The same numbers in the various figures can refer to the same structural component or part thereof. Additionally, the articles “a” and “an” preceding an element or component are intended to be nonrestrictive regarding the number of instances (i.e. occurrences) of the element or component. Therefore, “a” or “an” should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.
Spatially relative terms, e.g., “beneath,” “below,” “lower,” “above,” “upper,” and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures.
The following definitions and abbreviations are to be used for the interpretation of the claims and the specification. As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains” or “containing,” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, a mixture, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus.
As used herein, the term “about” modifying the quantity of an ingredient, component, or reactant of the invention employed refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or solutions. Furthermore, variation can occur from inadvertent error in measuring procedures, differences in the manufacture, source, or purity of the ingredients employed to make the compositions or carry out the methods, and the like.
It will also be understood that when an element, such as a layer, region, or substrate is referred to as being “on” or “over” another element, it can be directly on the other element or intervening elements can also be present. In contrast, when an element is referred to as being “directly on” or “directly over” another element, there are no intervening elements present, and the element is in contact with another element.
Turning now to
In step 110, a first powder layer including particles of the one or more metals and particles of the one or more ceramic materials is first provided on a suitable support. The first powder layer can be obtained by combining or mixing particles of the one or more metals and the one or more ceramic materials. In one or more embodiments, the particles of the one or more ceramic materials are uniformly dispersed throughout the powder bed. For example, the particles of the one or more metals and the one or more ceramic materials can be mixed together in a blender or mixer to provide a uniform mixture. In other embodiments, the powder bed can include different particle concentrations of the one or more ceramic materials within the layer.
In step 120, the layer is subjected to a selective melting AM process using a laser energy beam (or E-beam) to selectively melt a pattern in the powder layer followed by solidifying upon cooling to define a two-dimensional solidified image in the layer. The selective melting AM process generally includes exposing the powder layer to an incident energy beam, e.g., laser energy, e-beam energy, or the like, at an energy sufficient to reactively melt the pattern in the powder layer. The energy beam can be caused to move over the layer in a desired pattern to form a reacted portion of the layer and define the two-dimensional patterned image in the layer. The selective melting AM process can be conducted in an inert atmosphere, under vacuum, or under a partial vacuum.
In the case of an applied laser energy beam, the laser energy beam can be pulsed or continuous. Exemplary gas lasers suitable for use in the selective laser melting AM process can include a helium-neon laser, argon laser, krypton laser, xenon ion laser, nitrogen laser, carbon dioxide laser, carbon monoxide laser or excimer laser. Exemplary chemical lasers can include lasers such as a hydrogen fluoride laser, deuterium fluoride laser, COIL (chemical oxygen-iodine laser), or Agil (all gas-phase iodine laser). Exemplary metal vapor lasers can include a helium-cadmium (HeCd) metal-vapor laser, helium-mercury (HeHg) metal-vapor laser, helium-selenium (HeSe) metal-vapor laser, helium-silver (HeAg) metal-vapor laser, strontium vapor laser, neon-copper (NeCu) metal-vapor laser, copper vapor laser, gold vapor laser, or manganese (Mn/MnCl2) vapor laser. Exemplary solid state lasers include lasers such as a ruby laser, Nd:YAG laser, NdCrYAG laser, Er:YAG laser, neodymium YLF (Nd:YLF) solid-state laser, neodymium doped yttrium orthovanadate(Nd:YVO4) laser, neodymium doped yttrium calcium oxoborate. Nd:YCa4O(BO3)3 or simply Nd:YCOB, neodymium glass (Nd:Glass) laser, titanium sapphire (Ti:sapphire) laser, thulium YAG (Tm:YAG) laser, ytterbium YAG (Yb:YAG) laser, ytterbium:2O3 (glass or ceramics) laser, ytterbium doped glass laser (rod, plate/chip, and fiber), holmium YAG (Ho:YAG) laser, chromium ZnSe (Cr:ZnSe) laser, cerium doped lithium strontium (or calcium)aluminum fluoride (Ce:LiSAF, Ce:LiCAF), promethium 147 doped phosphate glass (147Pm+3:Glass) solid-state laser, chromium doped chrysoberyl (alexandrite) laser, erbium doped and erbium-ytterbium co-doped glass lasers, trivalent uranium doped calcium fluoride (U:CaF2) solid-state laser, divalent samarium doped calcium fluoride (Sm:CaF2) laser, or F-center laser. Exemplary semiconductor lasers can include laser medium types such as GaN, InGaN, AlGaInP, AlGaAs, InGaAsP, GaInP, InGaAs, InGaAsO, GaInAsSb, lead salt, Vertical cavity surface emitting laser (VCSEL), quantum cascade laser, hybrid silicon laser, or combinations thereof. For example, in one embodiment a single Nd:YAG q-switched laser can be used in conjunction with multiple semiconductor lasers. In other embodiments, E-beam can be used to cause the phase change in the metal-ceramic powder bed. In still other embodiments, E-beam can be used in conjunction with an ultraviolet semiconductor laser array. In yet other embodiments, a two-dimensional array of lasers can be used. In some embodiments with multiple energy sources, pre-patterning of an energy beam can be done by selectively activating and deactivating energy sources.
In the various commercially available additive manufacturing systems, the parameters defining the energy beam can vary widely. Generally, the power of selective laser melting additive manufacturing systems can be adjusted from about 10 to about 5000 W and will generally depend on the type of laser, the scanning velocity (which defines the exposure time) can be adjusted from about 100 mm/s to about 10,000 mm/s, hatch spacing (i.e., distance between adjacent scan lines) can be adjusted from about 10 μm to about 5000 μm, the energy density can range from about 10 J/mm3 to 10,000 J/mm3, the point distance can be in a range of about 10 μm to about 5000 μm, and layer thickness can be adjusted from about 10 μm to about 5,000 μm.
In step 130, the selective melting AM process is repeated by depositing one or more additional powder layers onto the first layer including the patterned layer and subjecting each additional patterned powder layer to the selective laser melting AM process to sequentially build the three-dimensional structure layer-by-layer. Typically, the patterns in the various layers defining the three-dimensional article are fabricated using a computer aided design (CAD) model.
Detailed embodiments of methods for forming the three-dimensional articles via selective laser melting AM processes and the resulting three-dimensional articles according to aspects of the present invention will now be described herein. However, it is to be understood that the embodiments of the invention described herein are merely illustrative of the process and structures that can be embodied in various forms. For example, as noted above, the selective melting AM processes can use E-beam to cause the phase change in the metal-ceramic powder bed. In addition, each of the examples given in connection with the various embodiments of the invention is intended to be illustrative, and not restrictive. Further, the figures are not necessarily to scale, some features can be exaggerated to show details of particular components. Therefore, specific structural and functional details described herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the methods and structures of the present description.
As noted above, in one or more embodiments, the selective laser melting AM process of a powder bed including ceramic particles dispersed in the metal particles matrix has been shown to increase energy transfer during the AM process. The optical properties, the thermal conductivity or a combination of the optical and thermal conductivities of the ceramic particles can be tailored in different areas within a given layer to change the energy absorption of the laser energy beam in the different areas. In this manner, ceramic reinforcement into metallic builds through reactive chemistry can produce crystalline structures and/or gradient materials that significantly improve performance of the three-dimensional structure including, but not limited to, increase in yield strength and tensile strength at room temperature and above while maintaining ductility, increase in creep resistance at higher temperatures compared to conventional alloys, increase in fatigue strength, improvement of thermal shock resistance, improvement of corrosion resistance, increases in Young's modulus, reduction of thermal elongation, among others.
The resulting MMC structure (MMC-type 316L steel) as shown in the micrograph of
As graphically shown in
In
As shown, the cast MMC type 316L steel relative to the additive manufactured type 316L steels exhibited significantly poor mechanical performance even when compared to the AM processed type-316L steel without ceramic reinforcement. As for the comparison between the AM type-316L with and without ceramic reinforcement, deformation of the AM processed MMC-type 316L steel was significantly less than that of the AM processed type 316L steel, i.e., about a 200 percent difference in stress compared to the type 316L steel. Clearly, strength properties such as Young's modulus, yield strength and ultimate tensile strength were markedly improved by AM processing of the type-316L with the addition of the ceramic particles when compared to the same composition without the ceramic particles, e.g., AM processed MMC-type 316L steel composition relative to the AM processed type-316L steel formed without the ceramic particles. Moreover, the increase in strength was obtained while maintaining ductility properties. Clearly, the use of selective laser additive manufacturing provides a significant advantage compared to convention casting and has the added benefit with formation of complex geometries unlike conventional casting methods. Moreover, a significant increase in mechanical properties can be provided with ceramic reinforcement.
In
It has been found that the interface. i.e., cell boundaries, includes sub-cellular networks within the reaction zone, which is believed to result in stabilization of the grain boundaries within the metal build resulting in the improved performance, wherein the ceramic material is not co-located within the cell boundaries. In the scanning electron micrographs illustrated in
In
As shown in
It has also been discovered that grain size decreased and the grains themselves became more equiaxed for the MMC metal builds such as the MMC-type 316L steel compared to the type 316L steel fabricated without the ceramic reinforcement.
In addition to significant increases in strength for the additive manufactured MMC-type 316L steel compared to the type 316L steel fabricated without the ceramic reinforcement, corrosion resistance was markedly improved. Corrosion resistance was generally measured in accordance with ASTM G48 but modified using a 30% and a 60% by weight FeCl3 solution to accelerate corrosion. A droplet of the FeCl3 solution was placed on a surface of each sample and exposed for 5 minutes (30% by wt. FeCl3 solution) or 50 minutes (60% by wt. FeCl3 solution). It was found that surface corrosion was minimal and uniform for the MMC-type 316L steel with no evidence of pitting or crevice formation. In contrast, surface corrosion was non-uniform with clear evidence of pitting and crevice formation for the type 316L steel without ceramic reinforcement.
As noted above, the laser utilized in the selective laser melting AM process can be pulsed or continuous. Similar strengthening effects have been observed for the different types of lasers.
Advantageously, MMCs formed by selective laser melt AM processing of powder beds including metal particles of one or more metals and ceramic particles of one or more ceramic materials provide a unique class of materials because their physical and mechanical properties can be dramatically tailored depending on the relative volume fraction of the metal and ceramic phases. MMC metal builds exhibit exceptional strength and corrosion performance that was not previously obtainable.
These and other modifications and variations to the invention may be practiced by those of ordinary skill in the art without departing from the spirit and scope of the invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and it is not intended to limit the invention as further described in such appended claims. Therefore, the spirit and scope of the appended claims should not be limited to the exemplary description of the versions contained herein.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/899,435, filed on Sep. 12, 2019, which is expressly incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62899435 | Sep 2019 | US |
