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2023 | Book

Additive Manufacturing with Metals

Design, Processes, Materials, Quality Assurance, and Applications

Authors: Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris

Publisher: Springer International Publishing

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About this book

This textbook and reference provides a comprehensive treatment of additive manufacturing (AM) for metals, including design and digital work flows, process science and reliability, metallic systems, quality assurance, and applications. The book is rooted in the fundamental science necessary to develop and understand AM technologies, as well as the application of engineering principles covering several disciplines to successfully exploit this important technology. As additive manufacturing of metals is the fastest growing subset of this transformative technology, with the potential to make the widest impact to industrial production, Metals Additive Manufacturing: Design, Processes, Materials, Quality Assurance, and Applications is ideal for students in a range of engineering disciplines and practitioners working in aerospace, automotive, medical device manufacturing industries.

Table of Contents

Frontmatter
Chapter 1. Introduction to Metal Additive Manufacturing
Abstract
This chapter introduces additive manufacturing (AM) with metals. A brief history of metal AM is provided through early AM patents. The classification of the various AM processes for metal is presented based on ASTM/ISO Standard Terminology. Additional classification based on material consolidation, heat source, and feedstock form is also provided. The benefits of using AM are discussed. The chapter concludes with an overview of the book, the organization, topics, and potential use of the book for teaching undergraduate and graduate courses.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 2. Digital Processing Workflow for AM
Abstract
This chapter introduces the complete workflow and processing steps necessary to convert a 3D design into a final manufactured part. Beginning with the input to the processes in the form of a digital data file in STL format, the STL format is described along with the limitations of this format. Typical errors encountered in STL files are discussed. Other representation formats such as AMF and 3MF and how they address the related issues with STL files are presented. The process of slicing and slicing algorithms and the implications of slicing are discussed. The typical process planning sequence, from build orientation, support structures, and tool path planning to parameters, is described, along with the implications arising from the decisions. The role of computer simulation as a step in the planning process along with 2D and 3D nesting to optimize a part build is also presented.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 3. Metal Additive Manufacturing Processes – Laser and Electron Beam Powder Bed Fusion
Abstract
This chapter introduces the two main powder bed fusion (PBF)-based AM processes used for metals. The laser-based PBF and electron beam-based PBF systems are discussed. For each process, a brief history of the process is provided, followed by a detailed description of the process and the major machine subsystems necessary for process execution. The primary binding mechanisms by which the powder is consolidated are presented. Process dynamics and process physics that drive the process at a fundamental level provide a deeper understanding of the process. Process parameters that control the formation of the melt pool and their relationships are presented. Brief descriptions of the materials, microstructure, and material properties are discussed. Process defects such as porosity, lack of fusion, thermal residual stress-related effects, and their causes are used to identify quality and process consistency issues. Advantages and disadvantages of each of the processes and a comparison between laser and ebeam systems are presented. Examples and applications of each of these processes are also presented.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 4. Metal Additive Manufacturing Processes – Directed Energy Deposition Processes
Abstract
Directed energy deposition (DED) is a major category of processes used for additive manufacturing of metal parts. The classification of this process based on type of feedstock and type of energy used has led to the development of a range of different DED processes. This chapter presents descriptions of powder-based and wire-based feedstock, using laser, Ebeam, plasma arc, and resistance heating-based processes. Powder feed, laser delivery, and motion control systems are discussed. The ability of these systems to deposit in three dimensions using robotic systems with additional rotary axis is described. The process dynamics are explained through the formation of the melt pool. Process parameters related to the process and their relationships are defined using the local energy density relationships. Materials used by the processes and microstructures formed are also described. Typical process defects and their potential causes are explored. Advantages and limitations of these processes are presented along with examples and applications.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 5. Metal Additive Manufacturing Processes – Jetting- and Extrusion-Based Processes
Abstract
This chapter covers the jetting- (binder jetting and material jetting) and extrusion-based processes. For each process, a brief history of the process is provided, followed by a detailed description of the process and the major machine subsystems necessary for process execution. The binder jetting process is described along with the process parameters that influence the process. The process dynamics are explained via the droplet formation and interaction with the substrate. Process parameters related to the powder feedstock material, liquid binder material, and machine bed parameters are discussed. The primary binding mechanism of sintering is introduced. Brief descriptions of the materials, microstructure, and material properties are discussed. The various material jetting approaches using solution-based deposition, Direct Droplet Deposition are presented. The extrusion-based process is also presented along with the process description and system components. Process dynamics of the extrusion process are explored through the models developed for various steps of the process. Materials used by the processes and microstructures formed are also described. Typical process defects and their potential causes are explored. Advantages and limitations of these processes are presented along with examples and applications.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 6. Metal Additive Manufacturing Processes – Deformation-Based AM and Hybrid AM Processes
Abstract
Deformation-based AM (also termed solid-state AM) processes do not use melting and solidification of material, but rely on plastic deformation mechanisms to create the bonding required for creation of the solid part layers during the build. This Chapter covers three major processes within this category – ultrasonic AM, cold spray, and additive friction stir welding. For each of these processes, a process description is provided. Process dynamics and key process parameters are discussed, along with the materials, microstructures, and material properties. Examples of parts are also provided to illustrate the capabilities of these processes. Hybrid AM processes that combine additive and subtractive manufacturing to take advantage of the strengths of each are gaining popularity as a recent development. The approaches taken by several commercial manufacturers are presented. DED based processes and powder bed-based hybrid processes are reviewed. Example parts showing the capability of the processes to produce multimaterial parts are presented.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 7. Design for Additive Manufacturing and Cost and Economics of AM
Abstract
Design for additive manufacturing (DfAM) refers to the design actions undertaken by the designer to take strategic advantage of the process capabilities offered by the AM process as well as incorporate the process limitations at the operational level to ensure that the design is manufacturable by the AM process in an economical manner. Detailed process knowledge and process capabilities are often required to create a successful AM design. This chapter provides an overview of the advantages of AM and how design/redesign can be used to maximize the impact of these advantages. General design principles are presented along with specific process-related requirements that influence the success and economics of the AM process. Topology optimization and its role in design optimization, along with different lattice structures and their influence on part design, are discussed. The chapter also addresses the cost and economics of AM. Several cost models are presented to illustrate the components of the cost models and how they can be used for decision-making at the design stage.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 8. Energy Sources and Propagation
Abstract
Key to fusion-based additive manufacturing (AM) of metals is an energy source to heat and melt a feedstock material. Lasers, electron beams, and electric arcs are among the most widely used for this purpose. This chapter covers the operating principles underlying each of these sources, propagation mechanisms, key variables affecting function, and common system configurations. Laser operating principles, including population inversion, stimulated emissions, formation of transverse modes, Gaussian and non-Gaussian beam propagation and focusing, along with common wavelengths and types are covered. Electron beam generation through thermionic emissions, acceleration, deflection, and focusing, and typical operating conditions are detailed. How electric arcs are formed, arc plasma properties, and arc system configurations are also discussed. A focus on foundation principles ensures that the concepts detailed here both are widely applicable to current-generation metal AM system and will remain relevant to emerging, next-generation processes.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 9. Source-Material Interactions
Abstract
Interactions between an energy source, feedstock, and the underlying substrate dictate the degree and profile of heating in and around the melt pool. In turn, these interactions control the size, shape, and stability of each deposited track or voxel along with the overall process speed and efficiency. Light, modeled as an electromagnetic wave, experiences refraction, reflection, attenuation, and absorption in and around the laser-interaction zone. Using principles presented in this chapter, it is possible to estimate the degree to which laser light, incident on a melt, solid, or powder substrate, will be reflected and absorbed. Electron beams operate using a different mechanism—heating via inelastic collisions of highly accelerated electrons. In contrast to laser beams, estimation of absorption and reflection is more complicated but is possible via semi-empirical methods. Electric arcs present yet another set of underlying interaction mechanisms. Energy is transferred by several mechanisms, including the flux of electrons and ions incident on the substrate, thermal conduction between the arc and the substrate, and light radiation from the arc. The degree to which each mechanism dominates and the overall process efficiency depend strongly on the arc type and configuration of the deposition process.
Irrespective of the energy source, all fusion-based processes result in heating, melting, and vaporization. Two melting regimes are typically considered: conduction-mode melting and keyhole-mode melting. While both modes are accompanied by vaporization and flow within the melt, keyhole-mode melting occurs when the pressure resulting from vaporization is high enough to form a deep vapor cavity, with a depth typically greater than the melt pool radius. Here, we detail models that are useful to elucidate heating, forces that drive flow within the melt, evaporation, melt ejection, and plasma interactions. The melt. Using the detailed frameworks presented in this chapter, it is possible to understand and model fundamental phenomena fusion AM processes related to source–material interactions.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 10. Feedstock Delivery and Dynamics
Abstract
The most commonly employed feedstocks in fusion additive manufacturing (AM) processes are wire and powder. Powders can of course be spread or sprayed, enabling a significant degree of process flexibility. However, characterization of powder feedstocks is complex, owing to the many specific and bulk properties, which may be influenced by production method, handling, and processing environments. Most fusion AM processes utilize powder produced by gas atomization or the plasma rotating electrode process, or variations thereof. The resulting powder can be characterized based on its specific properties—for instance, particle microstructure, chemistry, moisture content, and morphology—and based on the bulk powder properties—which include, packing behavior, flowability, rheology, and spreadability. Specific and bulk properties along with the feedstock delivery method influence densification, denudation, spatter formation, and the resulting track or voxel geometry.
In contrast to powders, wire feedstock are characterized by fewer variables. However, they require significant control of the position, shape, and speed of the wire relative to the substrate and energy source. In addition to wire diameter, the cast and helix of the wire impact the accuracy and precision of its delivery. The mode of feedstock transfer to the melt, broadly grouped as contact or free-flight transfer, depends on the source type, wire characteristics, and delivery method.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 11. Mechanical Response
Abstract
A primary failure mode of fusion AM processes is undesired distortion or cracking; the primary driver of which is residual stress, often combined with stress concentrating, voids, or inclusions. Simplified analogies help develop an intuitive understanding of the source of residual stress during fusion AM. To restrict distortion due to residual stress, support structures are often used, particularly in powder bed fusion processes.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 12. Analytical Models
Abstract
Analytical and computational models enable estimation of temperature near the melt pool. Among the most useful analytical models are the Rosenthal solution and the Eager and Tsai model. While the Rosenthal solution is limited to a model of a point source on a semi-infinite plate, it can be extended to account for more complex boundary conditions and finite-length sources using the method of images and virtual heat sources. To account for a Gaussian heat source, the Eager and Tsai model of a moving Gaussian source can be used. More realistic simulations, for instance, those accounting for nonlinear material response, complex geometry, and mechanical effects, require the use of computational methods. In a typical workflow, predictions of temperature are fed into microstructural models, which predict microstructure and mechanical properties. Together, the temperature history and mechanical properties are then used to predict residual stress and distortion. Fusion additive manufacturing processes also require consideration of material addition; this can be accomplished via element activation—three common modes of which are quiet, inactive, and hybrid quite/inactive element activation. In addition to developing these basic concepts, models for directed energy deposition and laser powder bed fusion are also presented.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 13. Alloy Systems for Additive Manufacturing
Abstract
A wide variety of metallic systems are used for additive manufacturing, with the selection of an appropriate material being based primarily on properties and characteristics required for the application. Alloy systems are described by the composition or constitution of the mixture, with the primary metallic element being used to define the family of alloy system, such as ferrous (iron-based) alloys, nickel alloys, titanium alloys, or aluminum alloys. Although alloys may be identified based on various designations or trade names, the unified numbering system has been developed to standardize the description of alloys and is used throughout this text. The alloy system and the specific additions govern the development of microstructure during processing and hence the resultant properties and characteristics that may be achieved. In many instances, the ideal alloy for additive manufacturing will display a combination of properties most appropriate for the intended application.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 14. Metallic Feedstock
Abstract
Almost all additive manufacturing processing utilize added material as feedstock. The most common forms of feedstock are metallic powder, for powder bed fusion, directed energy deposition, binder jetting, material jetting, and material extrusion processes, and wire, used exclusively for directed energy deposition. Several processes are used for producing metal powder for additive manufacturing, with various forms of atomization being the most common. The two primary methods for atomizing metallic powder are water or gas as the atomization medium, and high-quality powder is typically produced using controlled melting and inert gas atomization. Following atomization, powder is sieved to obtain the desired size distribution. Alternate processes are utilized for producing powder from refractory metals and hard particles, which in many instances entails chemical reactions to create the material, followed by mechanical reduction and sieving. Because of the influence powder feedstock exerts on the process and quality of the resultant material, great attention is paid to the physical and chemical characteristics of metal powder used in additive manufacturing. This includes how powder characteristics impact the reliability of the process based on the attributes of the powder aggregate, such as flowability, powder spreading, and packing. The most obvious physical characteristics of interest are the size distribution and shape of powder particles, with the bulk composition of the powder being the typical chemical characteristic of interest. Although these characteristics provide a foundation for describing general properties of the powder, they may not be sufficient for determining potential changes in powder attributes after storage, handling, use, and recycling. Other assessments, which may involve simulation of the powder aggregate for flow and packing to detailed quantitative analysis involving powder rheology, may also be utilized for evaluating the quality of the powder throughout its life.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 15. Solidification During Additive Manufacturing
Abstract
Two major categories of additive manufacturing, powder bed fusion and directed energy deposition, rely on solidification for fusing metal to form shapes. These processes utilize a moving heat source, such as a laser beam, electron beam, or electric arc, to cause rapid heating, melting, and solidification of the added material and the underlying substrate. The process of solidification establishes the initial microstructure of the fused material and hence, impacts properties and characteristics of the material produced during additive manufacturing. The projected spot size, power, and velocity of the heat source strongly influence the rate at which solidification occurs, which may be related to the scale of features formed during solidification, and ultimately, resultant mechanical properties. In the case of alloys representing more than one component, solidification takes place over a range of temperatures, bounded by the liquidus and solidus temperatures, and results in solidification proceeding through a gradual increase in the amount of solid being formed. The progression of the amount and composition of solid formed under equilibrium conditions may be described using an equilibrium phase diagram that defines the composition of the liquid and solid phases as a function of temperature. However, under conditions found during additive manufacturing, the equilibrium composition at the solid and liquid interface is not maintained and results in partitioning or redistribution of alloying additions during solidification. The occurrence of solute redistribution not only leads to microsegregation of constituents within the solidified microstructure but also effects the stability of the solid and liquid interface and is a major factor for establishing growth morphology, be it cellular, columnar dendritic, or equiaxed, during solidification. Utilizing the concept of constitutional supercooling for assessing stability of the solidifying interface, in combination with parameters that govern heat flow, processing maps may be developed to anticipate growth morphology and scale of solidification features. Ample examples and microstructures are used to illustrate this methodology, as well as validating its application.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 16. Solid State Transformations and Gas Reactions During the Additive Manufacturing Process
Abstract
In most instances the thermal response of the material during additive manufacturing does not result in melting and solidification but successive heating of the previously deposited material to elevated temperatures that are below the melting point. This results in changes in microstructure due to solid state transformations and has a significant effect on the resultant properties of the material. The specific characteristics of each thermal response governing solid state transformations that are operative include the peak temperature that is achieved, the cooling rate from the peak temperature, and the background temperature upon cooling. Generally, two broad categories of transformation may be identified to describe the changes in microstructure associated with many metals used for additive manufacturing: reactions that are primarily controlled by diffusion of atomic species and allotropic reactions that are governed by changes in crystallographic structure during cooling from an elevated temperature. In the latter, the rate of the reaction is: considerably slower than allotropic reactions. Materials for additive manufacturing that are dominated by diffusional reactions include most aluminum and nickel-based alloys, with some titanium alloys and many ferrous-based alloys governed by allotropic transformations. Non-isothermal (or anisothermal) reaction kinetics may be used to estimate the amount of transformation and the impact on mechanical properties under diffusional transformation, whereas the rate of cooling from the transformation temperature dictates the potential for an allotropic reaction to be active. Reactions between gaseous species and the material when in the liquid or solid state may also take place during processing, with potential ramifications being gas porosity, in the case of the former, or oxidation, for the latter. In some instances, gas reactions may be utilized in a positive fashion for inducing the creation of phases that may impart beneficial characteristics, such as in forming carbides or nitrides.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 17. Modeling of Microstructure for Additive Manufacturing
Abstract
The use of analytical and numerical techniques for modeling and simulation provides a powerful tool for developing greater insight into potential microstructural development and evolution during additive manufacturing. These techniques may be utilized to address very practical questions, such as determining the potential variability of microstructure and properties associated with thermal cycles representing a complex shape and path plan, identifying processing conditions that favor the establishment of desirable microstructures, and determining requirements for material grading to minimize non-desirable phases during multiple material processing. Although there are several approaches that may be used for theoretically representing development of microstructure, two techniques that are especially applicable to additive manufacturing are discussed and presented. These include phase field modeling of the solidification process and the Johnson-Mehl-Avrami-Kolmogorov procedure for following the evolution of microstructure during solid-state transformations. Both techniques require detailed information regarding the thermal response of the material at the location of interest.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 18. Multiple Alloy Processing
Abstract
In certain instances, it is desirable to change or modify the composition of the material produced using additive manufacturing. This is especially applicable to the directed energy deposition process where alterations to the feedstock material may be used to alter the composition, phases present, and characteristics of the deposited material. In the simplest case, a new material is deposited onto the substrate to impart improved properties at the surface for increased wear or corrosion resistance. In more extreme cases, the composition is altered elementally throughout the build to provide a graded composition that may avoid the formation of unwanted phases while also achieving improved properties and characteristics.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 19. Post Processing
Abstract
In almost all cases, parts, components, or structures produced using additive manufacturing techniques require some form of post processing and should be considered as an integral part of the additive manufacturing chain. These practices may be defined under broader categories that include thermal post processes, mechanical post processes, thermo-mechanical post processes, chemical post processes, and electrochemical post processes and are typically used in combination to impart the desired form, fit, and function required for meeting design specifications. Thermal post processing may be employed to reduce residual stresses that are inherent in many additive manufacturing techniques, alter the microstructure of the material to obtain improved mechanical properties, and provide greater chemical homogeneity throughout the part, which also results in more uniform properties. When an elevated temperature is combined with isostatic pressing, i.e., hot isostatic pressing, the process may be utilized to heal internal defects. Because of the influence the thermal practice may have on the resultant microstructure and properties, care must be taken to select the proper temperature and conditions based on the specific material being processed. There are also numerous methods used for modifying the geometry and finish of as-built part. This may entail traditional machining methods for attaining final geometry for additive processes that produce a “near-net shape” or the use of various post processing techniques to achieve greater part tolerance or improved surface finish that may not be available from additive manufacturing considered to be “net shape.” The exact finishing processes that may be applied are also chosen based on meeting requirements established during design.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 20. Properties and Characteristics of Metallic Materials Produced Using Additive Manufacturing
Abstract
The application of additive manufacturing ultimately relies on the process and resultant material meeting properties and characteristics that are established during design. In this regard, the process is defined as the selection of a material that when paired with an additive manufacturing process and secondary post-processing is capable of meeting the form, fit, and function requirements needed to satisfy the intended application. This is accomplished by inspection of various physical attributes of the part and testing of the material, in many instances, during the development stage. Properties of the material that are used during design may include the ultimate strength or yield strength, elongations to assess ductility, toughness, and fatigue strength, if service involves cyclic loading. When the application involves potential degradation due to the environment, corrosion resistance is an important factor. Published results of tensile, fatigue, and fracture toughness tests for a variety of materials and additive processes are presented and discussed. When possible, properties are tabulated to allow comparison to post processing conditions, as well as material representing wrought product forms. Results of laboratory electrochemical measurements for ascertaining corrosion potential of several alloys produced using additive manufacturing and used in corrosive environments are also presented and, when available, compared to wrought material.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Chapter 21. Process Quality and Reliability
Abstract
Traditional process performance qualification approaches, with some modifications, can be successfully applied to metal additive manufacturing. This requires a cycle of design verification, process definition, material qualification, qualification of the processing system, and continuous performance qualification. Although this approach can be laborious, especially when applied initially, it does ensure that important parameters and aspects of the process are identified, controlled, and repeatable. Through the use of sensor-based quality monitoring, process qualification may be accelerated while also enabling observations as to the state of the process and the condition of the material being produced. Today, many commercial systems incorporate in situ process sensors and, in some cases, closed-loop control. In the coming years, continued development of methods and data analytics are likely to lead to greater assurance in process and part quality.
Sanjay Joshi, Richard P. Martukanitz, Abdalla R. Nassar, Pan Michaleris
Backmatter
Metadata
Title
Additive Manufacturing with Metals
Authors
Sanjay Joshi
Richard P. Martukanitz
Abdalla R. Nassar
Pan Michaleris
Copyright Year
2023
Electronic ISBN
978-3-031-37069-4
Print ISBN
978-3-031-37068-7
DOI
https://doi.org/10.1007/978-3-031-37069-4

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