【国外标准】 Standard Guide for Directed Energy Deposition of Metals

5.1 This guide applies to directed energy deposition (DED) systems and processes, including electron beam, laser beam, and arc plasma based systems, as well as applicable material systems.5.2 Directed energy deposition (DED) systems have the following general collection of characteristics: ability to process large build volumes (>1000 mm3), ability to process at relatively high deposition rates, use of articulated energy sources, efficient energy utilization (electron beam and arc plasma), strong energy coupling to feedstock (electron beam and arc plasma), feedstock delivered directly to the melt pool, ability to deposit directly onto existing components, and potential to change chemical composition within a build to produce functionally graded materials. Feedstock for DED is delivered to the melt pool in coordination with the energy source, and the deposition head (typically) indexes up from the build surface with each successive layer.5.3 Although DED systems can be used to apply a surface cladding, such use does not fit the current definition of AM. Cladding consists of applying a uniform buildup of material on a surface. To be considered AM, a computer aided design (CAD) file of the build features is converted into section cuts representing each layer of material to be deposited. The DED machine then builds up material, layer-by-layer, so material is only applied where required to produce a part, add a feature or make a repair.5.4 DED has the ability to produce relatively large parts requiring minimal tooling and relatively little secondary processing. In addition, DED processes can be used to produce components with composition gradients, or hybrid structures consisting of multiple materials having different compositions and structures. DED processes are also commonly used for component repair and feature addition.5.5 Fig. 1 gives a general guide as to the relative capabilities of the main DED processes compared to others currently used for metal additive manufacturing. The figure does not include all process selection criteria, and it is not intended to be used as a process selection method.FIG. 1 Comparison of Various Metal Additive Manufacturing ProcessesNOTE 1: In this figure, Build Volume refers to the relative size of components that can be processed by the subject process. Detail Resolution refers to the ability of the process to create small features. Deposition Rate refers to the rate at which a given mass of product can be produced. Coupling Efficiency refers to the efficiency of energy transfer from the energy source to the substrate, and Potential for Contamination refers to the potential to entrain dirt, gas, and other possible contaminants within the part.1.1 Directed Energy Deposition (DED) is used for repair, rapid prototyping and low volume part fabrication. This document is intended to serve as a guide for defining the technology application space and limits, DED system set-up considerations, machine operation, process documentation, work practices, and available system and process monitoring technologies.1.2 DED is an additive manufacturing process in which focused thermal energy is used to fuse materials by melting as they are being deposited.1.3 DED Systems comprise multiple categories of machines using laser beam (LB), electron beam (EB), or arc plasma energy sources. Feedstock typically comprises either powder or wire. Deposition typically occurs either under inert gas (arc systems or laser) or in vacuum (EB systems). Although these are the predominant methods employed in practice, the use of other energy sources, feedstocks and atmospheres may also fall into this category.1.4 The values stated in SI units are to be regarded as standard. All units of measure included in this guide are accepted for use with the SI.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.