Patent Application
20190091768
The embodiments herein generally relate to manufacturing processes, and more particularly to three-dimensional/additive manufacturing (3D/AM) processing.
There are several critical technology gaps that must be addressed to enable 3D/AM to accelerate away from prototypes and mold/die production toward production of finished parts. For example, finished parts production is an enabler for providing the defense industry with a threat responsive capability to deal with unknowns and surprises on the battlefield, and to reduce logistics burdens. Highlighted are two critical gaps: one is the ability to realize in-line certification of finished parts and the other is to control the processing-structure-property-performance relationships from 3D/AM machines. Controlling the final properties will enable 3D/AM to produce structural components.
Laser based 3D printing systems are designed specifically for processing of metals. These processes rely on local melting and re-solidification of the powder bed which typically results in non-ideal microstructure and properties and may also introduce defects such as porosity and non-equilibrium inclusions or precipitates. The high temperatures associated with laser based AM methods also results in high residual stresses and distortions which may render the part unusable or require additional post processing and associated time and costs.
In view of the foregoing, an embodiment herein provides an apparatus comprising a pair of electrodes comprising a first electrode and a second electrode; a power supply operatively connected to the pair of electrodes; and an area in between the pair of electrodes that holds a material, wherein the first electrode is configured for flash sintering the material. The first electrode may be movable. The first electrode may comprise a stylus. The material may comprise powder. The material may comprise any of metallic and ceramic material. The apparatus may further comprise multiple layers of materials flash sintered by the first electrode. The first electrode may generate an electric field between the first electrode and the material causes the flash sintering. The apparatus may further comprise a nozzle that supplies the material, wherein the nozzle is configured to supply the material at variable speeds. The first electrode may be configured to move at variable speeds and in variable directions. The flash sintering may occur at an electric field between 10-50000 V/cm and an electric current between 0-30 A.
Another embodiment provides a method comprising positioning a pair of electrodes comprising a first electrode and a second electrode; positioning material in between the pair of electrodes; and applying an electric field between the first electrode and the material causing flash sintering of the material. The method may further comprise moving the first electrode over the material. The material may comprise powder. The material may comprise any of metallic and ceramic material. The method may further comprise applying additional material after the flash sintering; and performing another flash sintering process. The method may further comprise forming multiple layers of sintered material. The method may further comprise shaping the multiple layers into a 3D structure. The method may further comprise supplying the material at variable speeds. The method may further comprise moving the first electrode at variable speeds and in variable directions. The flash sintering may occur at an electric field between 10-50000 V/cm and an electric current between 0-30 A.
These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:
The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The embodiments herein provide a flash sintering process to enable 3D printing or AM. The embodiments herein use electric field effects to rapidly sinter materials additively to form bulk solid components. Referring now to the drawings, and more particularly to
The embodiments herein provide an AM technique for fabrication of 3D metallic and ceramic components of complex geometry on demand. The technique provided by the embodiments herein uses electric fields to exploit flash sintering phenomena and to rapidly sinter powder feedstocks. The process uses a low current, high voltage flash sintering process to fuse powders into dense structures at significantly lower temperatures and faster rates than conventional processes.
The embodiments herein exploit flash processing, which enables material consolidation at significantly lower temperatures (on the order of hundreds of degrees Centigrade below traditional sintering) and at significantly higher rates (from several hours in conventional processing to tens of seconds using the embodiments herein). Low temperature sintering within a narrow spatial extent enables incorporating flash technology into an additive processing system to deposit material in complex geometries and create valuable components and finished products. The flash sintering process typically uses electric fields on the order of 10-50000 V/cm and electric currents between 0-30 A. The electric field enhances the thermodynamics and kinetics of consolidation. The flash phenomenon describes the point at which the material 35 rapidly densifies and is associated with a change in electrical conductivity of the material from insulating to conducting. The flash phenomenon is ideally suited for exploitation in an additive manufacturing tool. The tip 20 of the movable electrode 25 is brought into close proximity to the powder 35, as further shown in
The embodiments herein address the gap of micro-structural control, which the conventional solutions have not been able to provide. One aspect of the embodiments herein create microstructures with desirable properties/performance) at lower temperatures. The reduction in processing temperature may be greater than 800° C., which is quite substantial for reduction of costs, and enables manufacture of materials with unique microstructures and properties not obtainable through conventional techniques. In addition, the techniques of exploiting “flash technology” in 3D/AM as provided by the embodiments herein permits very short manufacturing times (e.g., hours) to produce complex components. Lower temperatures and shorter manufacturing times reduce cost and provide a means to produce parts from ceramics with new microstructures compared to conventional techniques. The embodiments therein, therefore lower costs, enables new finished or near net shape components, and increases availability. Polymers and metals dominate the 3D/AM space. Accordingly, the technique provided by the embodiments herein opens new markets in ceramics. The embodiments herein also apply to metal 3D/AM processing, and again offers reduced temperature processing and access to new properties through control of the microstructure.
The embodiments herein provide on-demand manufacturing in support of agile expeditionary forces, on-demand manufacturing of complex geometry components for light weighting efforts and rapid prototyping, and allow for rapid production of 3D printed components and for the repair of damaged components. The flash processing techniques utilized by the embodiments herein enables densifying materials that cannot be utilized in traditional AM or sintering processes. The embodiments herein are able to fuse powders into dense structures at significantly lower temperatures and faster rates than conventional processes such as Direct Metal Laser Sintering (DMLS), Laser Engineered Net Shaping (LENS), and arc welding. The process provided by the embodiments herein involves solid state processing which has advantages of preserving microstructures of starting feedstocks, including nanocrystalline structures. The process provided by the embodiments herein is not limited to metals, and enables much lower temperature sintering and processing of wide range of materials, including AM of ceramics, and multi-material processing with a single apparatus 10. Accordingly, the embodiments herein may be utilized in several types of diverse applications including the rapid prototyping of a wide range of materials, complex geometry components, agile expeditionary manufacturing, reduce logistic burden of soldiers in field, repair and sustainment of existing systems/components, 3D printed ceramics, 3D printed composite structures, 3D printed metallic structures, 3D printed nanomaterials, and 3D printed biomaterials.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.
The embodiments herein may be manufactured, used, and/or licensed by or for the United States Government without the payment of royalties thereon.
