Metal Additive Manufacturing E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 1065

Veröffentlichungsjahr: 2025

Beschreibung

This informative and practical guide to metal additive manufacturing explores techniques, applications, and future advancements.

Metal additive manufacturing stands as a revolutionary technology and a rapid prototype for engineering applications. In the realm of advanced manufacturing, it has long been a driving force in the development of AM metal technology. Moreover, it is now paving the way for high-value manufacturing components blended with sophisticated materials.

The book examines this rapidly evolving field and elucidates the foundations of metal additive manufacturing, including its various technologies, material design principles, and extrusion processes. Real-world applications are showcased, with examples from the aerospace, automotive, and healthcare industries, demonstrating the practical impact of metal AM. Chapters thoroughly discuss the evolution of manufacturing techniques, classifications of AM technologies, and the critical role of characterization in ensuring quality. The book emphasizes the importance of metal AM processes and their transformative potential for modern manufacturing. It concludes with coverage of future trends and advancements in additive manufacturing.

Audience
The book equips manufacturing and production engineers, researchers, and professionals with metal AM knowledge for the production of high-value components, driving innovation and efficiency in manufacturing.

Leseprobe

Table of Contents

Cover

Table of Contents

Series Page

Title Page

Copyright Page

Preface

1 Technologies for Additive Manufacturing of Metals and Their Classification

1.1 Introduction

1.2 Metal Additive Manufacturing Process (MAMP)

1.3 Classification of MAMP Based on Technologies

1.4 Liquid-Based MAMP: Liquid Metal 3D Printing

1.5 Solid-Based MAMP: Ultrasonic Additive Manufacturing

1.6 Powder-Based MAMP

1.7 Wire-Based MAMP: Wire DED

1.8 Applications

1.9 Conclusion

References

2 Challenges and Complications in Metal Additive Manufacturing During Post Processing

2.1 Introduction

2.2 Various Post Processing Methods

2.3 Future Scope and Aspects

2.4 Conclusion

References

3 Mechanics and Modeling of Metal Additive Manufacturing Using Directed Energy Deposition Method

3.1 Introduction

3.2 Computational Modeling

3.3 Nucleation Modeling

3.4 Conclusion

References

4 Rapid Additive Manufacturing of Metals Using the Cold Spray Technology: Progress and Challenges

4.1 Introduction

4.2 Progress in Cold Spraying Towards an Implementation as a Fast AM Route for Metals

4.3 Processing Science of Cold Spraying from Coating to Additive Manufacturing

4.4 Cold Spraying Modern System for an Additive Manufacturing Application

4.5 Robotic Technology and Computerized Program Execution in Cold Spraying

4.6 Robotic Programming and Deposition Strategy for CSAM

4.7 Current Achievements in CSAM of Metallic Parts

4.8 Porosity Issue Due to the Additive Growth and Methods for Pore Reduction

4.9 Issue of Clogging in CSAM and Concept of Aerospike Nozzle as Potential Solution

4.10 Future Research Directions

4.11 Conclusion

References

5 Principles of Material Extrusion in Metal Additive Manufacturing

5.1 Introduction

5.2 Additive Manufacturing Technology

5.3 Basic Additive Manufacturing Methods

5.4 Extrusion Principle

5.5 Metal Extrusion with Additive Manufacturing

5.6 Industrial Applications and Examples

5.7 Future Potential and Innovative Approaches

5.8 Conclusion

References

6 Material Design: A ‘Material’ Way to Improve Additive Manufacturing

6.1 Introduction

6.2 Conventional Alloys for MAM

6.3 Limitations of Conventional Alloys for MAM

6.4 Material Design for Metal Additive Manufacturing

6.5 Alloys Designed for AM

6.6 Perspective and Future Directions

6.7 Summary

References

7 Metal Powder Feedstock Production for Additive Manufacturing

7.1 Introduction

7.2 Different Stages in Metal Powder Production

7.3 Feedstock Selection

7.4 Processes

7.5 Powder Processing

7.6 Discussion

7.7 Conclusion

Acknowledgments

References

8 Additive Manufacturing of Intermetallic-Based Alloys: A Review

8.1 Introduction

8.2 Basic Properties of Intermetallic Alloy

8.3 Additive Manufacturing Techniques

8.4 NiAl-Based Alloys

8.5 Metallurgical Defects

8.6 Microstructure

8.7 Mechanical Properties

8.8 Ni

3

Al-Based Alloys

8.9 Metallurgical Defects

8.10 Microstructure

8.11 Mechanical Properties

8.12 TiAl-Based Alloy

8.13 Microstructure

8.14 Mechanical Properties

8.15 Conclusion and Perspectives

Acknowledgments

References

9 Mechanical Behavior of 3D Printed Parts

9.1 Introduction

9.2 Metal AM and its Classification

9.3 Metal AM Processes and the Mechanical Properties of Printed Parts

9.4 Effect of Post-Processing on the Mechanical Properties of 3D Printed Metal Parts

9.5 Challenges and Opportunities for Metal AM

9.6 Conclusion

References

10 Processing of Hydrogels with Metallic Additives in Additive Manufacturing

10.1 Introduction

10.2 Methods for Incorporating Metal Additives into Hydrogels

10.3 Metal Additives from Physical Cross-Linking Processes

10.4 Metal Additives as Metal Powder Feedstock

10.5 Metal Additives as Metal Nanoparticles

10.6 Application Areas for Hydrogels with Metallic Additives

10.7 Future Perspectives and Conclusions

References

11 Additive Manufacturing Simulation: Molten Pool Dynamics, Solidification Microstructure, and Powder Behavior

11.1 Introduction

11.2 Simulation of Molten Pool Dynamics

11.3 Simulation of Grain Structure

11.4 Simulation of Dendrite Growth

11.5 Simulation of Powder Behavior

11.6 Conclusion and Future Prospects

References

Appendix

12 Underlying Principles and Applications of Cold Spray Additive Manufacturing

12.1 Introduction

12.2 Emergence of Cold Spray Additive Manufacturing

12.3 Variables Affecting the CS Consolidations

12.4 Bonding Mechanism in CSAM

12.5 Locked Up Stresses in CSAM

12.6 Type of Structure Fabricated Using CSAM

12.7 Applications

References

13 Comparison of Different Metal Additive Manufacturing Techniques for Biomedical Application

13.1 Introduction

13.2 Powder Bed Fusion (PBF)

13.3 Binder Jetting (BJ)

13.4 Material Extrusion (MEX)

13.5 Direct Energy Deposition (DED)

13.6 Sheet Lamination (SHL)

13.7 Material Jetting (MJ)

13.8 Conclusion

13.9 Future Direction and Challenges

References

14 Application of Metal Additive Manufacturing for Metal Matrix Composites

14.1 Introduction

14.2 Metal Matrix Composite (MMC)

14.3 Additive Manufacturing of MMCs

14.4 Techniques of Metal Matrix Composites-Based Additive Manufacturing (AM)

14.5 MMCs Processing by 3D Printing

14.6 Application of Additive Manufacturing Product

14.7 Key Challenges

14.8 Summary and Future Work

References

15 Transforming Supply Chains (SCs) with Additive Manufacturing (AM): A Paradigm Shift in Production

15.1 Introduction

15.2 AM in Supply Chain Management

15.3 Impact of AM in Supply Chain

15.4 Smart Supply Chain with AM

15.5 AM Contribution to Flexibility in the Intelligent Supply Chain

15.6 Supply Chain Framework for AM

15.7 Supply Chain Structure Impacts of AM

15.8 Traditional Manufacturing (TM)

15.9 Spare Part Management

15.10 AM in Apparel Industry

15.11 Benefits of AM in Supply Chain

15.12 Cyber Risks in the AM Supply Chain

15.13 Barriers in AM Implementation in Supply Chain

15.14 Conclusion

References

16 Multi-Material Additive Manufacturing for Biomedical Applications

16.1 Introduction

16.2 Additive Manufacturing of Multi-Materials for Biomedical Applications

16.3 Additively Manufactured Multi-Material Components for Bio-Medical Applications

16.4 Conclusion

Acknowledgment

References

17 Digital Light Processing (DLP)–Based Three-Dimensional Printing for Biomedical Applications

17.1 Introduction

17.2 Photocurable Materials

17.3 Photoinitiators

17.4 Synthesis of the Hydrogel

17.5 Applications in Biomedical Engineering

17.6 Conclusion and Future Aspects

Acknowledgment

References

18 Salient Aspects of 3D Printed Microfluidic Device–Based Organ-on-a-Chip Models for Futuristic Healthcare Applications

18.1 Introduction

18.2 Biodegradable Materials for the Organ-on-a-Chip Model

18.3 Fabrication of MFDs Through 3D Printing

18.4 Evolution and Applications of Microfluidic Chips

18.5 Conclusion

Acknowledgment

References

19 Smart Hydrogels for Tissue Engineering Applications

19.1 Introduction

19.2 Classification of Smart Hydrogels

19.3 Synthesis of Smart Hydrogels

19.4 Applications of Smart Hydrogels for Tissue Engineering

19.5 Conclusion

Acknowledgment

References

Index

End User License Agreement

List of Tables

Chapter 4

Table 4.1 Overview of the potentials of cold spraying [1].

Table 4.2 Porosity comparison between a traditional deposition and a compensat...

Chapter 6

Table 6.1 Features of different AM technologies.

Chapter 7

Table 7.1 Characteristics of metal powder derived from various manufacturing p...

Chapter 8

Table 8.1 Compressive mechanical properties of some NiAl-based alloys at room ...

Table 8.2 Room temperature and high temperature tensile mechanical properties ...

Table 8.3 Room temperature tensile mechanical properties of some TiAl alloys.

Chapter 9

Table 9.1 Some research work done to improve the mechanical properties via pos...

Chapter 10

Table 10.1 Metallic nanoparticles used in PDT and PTT.

Chapter 11

Table 11.1 Notation table.

Chapter 13

Table 13.1 Comparison of some of the mechanical parameters of natural bone tis...

Chapter 14

Table 14.1 Various 3D printed parts of the aircraft.

Table 14.2 Numerous 3D printed automotive components.

Chapter 15

Table 15.1 Description of AM in various industries.

Table 15.2 The impacts of AM on the supply chain.

Table 15.3 Difference between traditional and additive supply chain.

Chapter 16

Table 16.1 Applications of polymer-based MMAM.

Table 16.2 Polymer and metal/ceramic materials for biomedical applications.

Table 16.3 Multi-materials for bone scaffolds.

Chapter 17

Table 17.1 Biomaterials commonly used for DLP-3D printing.

Table 17.2 Overview of important photoinitiators.

Chapter 18

Table 18.1 Characteristics of various biodegradable materials used for microfl...

Table 18.2 Advantages and disadvantages of 3D printing methods.

Table 18.3 Summary of 3D printed organ-on-a-chip microfluidic models.

Chapter 19

Table 19.1 Summary of various types of chain-growth polymerization techniques.

Table 19.2 Smart hydrogels in different tissue engineering and biomedical appl...

List of Illustrations

Chapter 1

Figure 1.1 Metal additive manufacturing process [2].

Figure 1.2 Flow chart of various additive manufacturing techniques.

Figure 1.3 Working principle of liquid-based printing [8].

Figure 1.4 Working principle of ultrasonic additive manufacturing [10].

Figure 1.5 Working principle of binder jetting [13].

Figure 1.6 Working principle of powder-based DED [14].

Figure 1.7 Schematic diagrams of the LC processing mode: (a) coaxial powder fe...

Figure 1.8 Schematic diagram of the LC system with the coaxial powder feeding ...

Figure 1.9 Schematic of a typical PBF machine [24].

Figure 1.10 Schematic of EBM system [28].

Figure 1.11 Schematic of SLS [37].

Figure 1.12 Working principle of WAAM [39].

Figure 1.13 Working principle of WAAM [40].

Figure 1.14 Schematic setup of wire arc additive manufacturing.

Figure 1.15 Arc column in welding.

Figure 1.16 Setup for gas metal gas arc welding.

Figure 1.17 Schematics of the setup of GTAW.

Figure 1.18 Various phases in CMT welding.

Figure 1.19 Plasma arc-based WAAM [61].

Chapter 2

Figure 2.1 Types of additive manufacturing.

Figure 2.2 Deposited layers by AM.

Figure 2.3 A typical TIG-WAAM setup.

Figure 2.4 A GMAW setup.

Figure 2.5 Friction stir processing.

Figure 2.6 Laser peening process.

Chapter 3

Figure 3.1 Classification of DED.

Chapter 4

Figure 4.1 Taxonomy of current cold spray method variances depicted by a diagr...

Figure 4.2 Typical powder granulometry in CS (a) and critical bonding velocity...

Figure 4.3 Architecture of CGDS set-up and typical nozzle DOF, along with subs...

Figure 4.4 Illustration of additive growth in cold spraying towards a gaussian...

Figure 4.5 Compensation strategy in cold spraying for alleviating the gaussian...

Figure 4.6 Cold spray production of bulk component using the traditional strat...

Figure 4.7 Typical 3D functional part produced by CSAM with an optimal deposit...

Figure 4.8 Typical CSAM of metallic structure with a possibility of a high pro...

Figure 4.9 Cold spray additive manufacturing of diverse complex parts using th...

Figure 4.10 Phenomenological deposit formation in CGDS for metallic particles ...

Figure 4.11 Particle deformation during the additive growth in cold spraying t...

Figure 4.12 Porosity within a Ti6Al4V cold spray deposit during the additive g...

Figure 4.13 Properties of Ti6Al4V deposits produced by cold spray additive man...

Figure 4.14 Proof of concept for the enactment of the aerospike nozzle princip...

Figure 4.15 A prowess combining strategies of cold spray deposition with desig...

Chapter 5

Figure 5.1 Additive manufacturing process.

Figure 5.2 Basic additive manufacturing methods.

Figure 5.3 Fused deposition modeling.

Figure 5.4 Stereolithography.

Figure 5.5 Selective laser sintering.

Figure 5.6 Electron beam melting.

Figure 5.7 Digital light processing.

Figure 5.8 Material extrusion with additive manufacturing.

Figure 5.9 Extrusion of metal materials.

Figure 5.10 Industrial applications of extrusion.

Chapter 6

Figure 6.1 Classification of AM technologies.

Figure 6.2 The size and structural complexity of components fabricated by diff...

Figure 6.3 Tendency of defects formation in typical alloys fabricated by MAM.

Figure 6.4 Hot cracking phenomenon in Al-, Ni-, and Ti-based alloys [63].

Figure 6.5 (a) Variation of solid fraction with temperature and (b) variation ...

Figure 6.6 The microstructure of Al–Zn–Mg alloys (a) with Si and (b) without S...

Figure 6.7 Grain structure of SLM (a) Al alloy, and (b) AlSi10Mg alloy with Ti...

Figure 6.8 (a) Crystal structure of Al3(Sc,Zr) and Al, (b) typical grain struc...

Figures 6.9 The interrelationship of (a) solidification range and (b) creep pr...

Chapter 7

Figure 7.1 Metal powder production processes for additive manufacturing [9].

Figure 7.2 Different stages in the metal powder production [9].

Figure 7.3 Freefall atomization process [26].

Figure 7.4 Close-coupled gas atomization process [26].

Figure 7.5 Schematic of high-pressure gas atomization process and nozzle struc...

Figure 7.6 Electrode-induction melting gas atomization process [9].

Figure 7.7 Atomizer nozzle in the electrode-induction melting gas atomization ...

Figure 7.8 Water atomization process [9].

Figure 7.9 (a) Plasma atomization equipment, (b) schematic of plasma atomizati...

Figure 7.10 Centrifugal atomization process [45].

Figure 7.11 Centrifugal atomization with gas jet [9].

Figure 7.12 Melting spinning process [49].

Figure 7.13 Rotating electrode process [53].

Figure 7.14 Plasma rotating electrode process [53].

Figure 7.15 Grinding process [57].

Figure 7.16 Crushing process [59].

Figure 7.17 Mechanical alloying method for powder production [62].

Figure 7.18 An overview of oxidation and chemical reduction of graphene [66].

Figure 7.19 Electrochemical reduction of low titanium chloride pulp to titaniu...

Figure 7.20 An overview of hydrometallurgical technique [80].

Figure 7.21 Hydrometallurgical treatment for recovery of various metals from t...

Figure 7.22 The modification of carbonyl iron powder surface for interaction i...

Figure 7.23 Laser ablation process for powder production [86].

Figure 7.24 (a) Experimental setup for ultrasonic spray pyrolysis and (b) form...

Figure 7.25 Microwave plasma synthesis process [97].

Figure 7.26 Combustion synthesis technique [100].

Figure 7.27 Spark erosion apparatus for powder production [106].

Figure 7.28 Metal particle shapes based on dimensionality [118].

Figure 7.29 Different shapes of the metal powder [9].

Chapter 8

Figure 8.1 (a) The radiant burner tube made of IC-221M alloy (Weirton Steel Co...

Figure 8.2 Crystal structure of NiAl.

Figure 8.3 Yield stress as a function of temperature for (a) several different...

Figure 8.4 Crystal structure of Ni

3

Al.

Figure 8.5 Comparison of yield strength of Ni

3

Al alloys (advanced aluminide al...

Figure 8.6 Crystal structure of the phase of TiAl alloy. (a) γ-TiAl phase; (b)...

Figure 8.7 Schematic diagram of L-PBF technology.

Figure 8.8 Schematic diagram of DED technology based on: (a) powder feed depos...

Figure 8.9 (a) Crack in the remelted layer, (b) the macrostructure of the tran...

Figure 8.10 SEM image of the microstructure of Ni42Al51Cr3Mo4 alloy (a) L-PBF ...

Figure 8.11 Microstructure (XY cross-sections) of the samples produced by L-PB...

Figure 8.12 (a) Phase distance of NiAl- and (Cr, Mo)-phases as a function of t...

Figure 8.13 (a) Microstructure of the cross-section of spherical Ni41Al41Cr12C...

Figure 8.14 Microstructures (XY cross-sections) of the samples produced by L-P...

Figure 8.15 (a) Increasing hardness with decreasing phase distance. (b) Series...

Figure 8.16 Four types of cracks in Ni

3

Al-based alloys prepared by additive ma...

Figure 8.17 Microstructure of the as-built IC-221M samples. SEM images on the ...

Figure 8.18 OM morphology of experimental multiphase Ni

3

Al-based intermetallic...

Figure 8.19 Microstructural characterization of Ni

3

Al-based alloy prepared by ...

Figure 8.20 Optical micrographs of the L-DED produced (a, c) and the L-PBF-pro...

Figure 8.21 Mechanical properties of the T-WAAMed Ni

3

Al-based alloy: (a) engin...

Figure 8.22 (a) Schematic drawing for a double laser setup for L-DED; (b) a no...

Figure 8.23 Top view schematic of linear scanning (a and b) and circular oscil...

Figure 8.24 Relationship between the energy density (

E

density

) and the apparen...

Figure 8.25 (a) IPF and (b) phase maps of LPBF Ti–43Al–9V-0.5Y samples without...

Figure 8.26 Microstructure and sketch image of L-DED TiAl alloy (a) schematic ...

Figure 8.27 (a) SEM images of EBM formed TiAl alloy sample with high line ener...

Chapter 9

Figure 9.1 Basic process steps of AM process.

Figure 9.2 Classification of metal AM.

Figure 9.3 Schematic diagram of the LPBF process.

Figure 9.4 Schematic diagram of the EBPBF process.

Figure 9.5 Variation of ultimate compressive strength of the Ti64 fabricated b...

Figure 9.6 Schematic diagram of the metal BJ process.

Figure 9.7 Schematic diagram of the LDED process.

Figure 9.8 Schematics diagram of EB-DED process.

Figure 9.9 Schematics diagram of WAAM process.

Figure 9.10 Influence of (a) laser power, (b) scanning speed, and (c) powder f...

Figure 9.11 Micro-hardness and wear rate of the aluminum alloys [34].

Figure 9.12 Tensile properties of the parts fabricated with different heat inp...

Figure 9.13 Schematic diagram of the UAM process.

Chapter 10

Figure 10.1 Metal additives applied in additive manufacturing of hydrogels in ...

Figure 10.2 (a) CAD starfish design, (b–d) 3D printed SLA hydrogel starfish wi...

Figure 10.3 General scheme of PDT.

Chapter 11

Figure 11.1 Molten pool scale flow simulation via FVM and VOF.

Figure 11.2 Molten pool scale flow simulation via ALE.

Figure 11.3 Molten pool scale flow simulation via LBM.

Figure 11.4 Molten pool scale grain growth simulation via CA.

Figure 11.5 Molten pool scale grain growth simulation via MPF.

Figure 11.6 Simulation and experiment results of molten pool scale grain struc...

Figure 11.7 Meso-scale dendritic growth simulation via CA.

Figure 11.8 Meso-scale dendritic growth simulation via QPF.

Figure 11.9 Powder behavior simulation via DEM.

Chapter 12

Figure 12.1 Schematic representation of cold spray technique.

Figure 12.2 The schematic representation of cold spray (CS) De Laval nozzle wi...

Figure 12.3 Various process variables in cold spray additive manufacturing (CS...

Figure 12.4 The cold spray (CS) structural integrity with and without substrat...

Chapter 13

Figure 13.1 Fields of application of additive manufacturing methods in biomedi...

Figure 13.2 General selective laser sintering (PBF-LB/P/(SLS))/selective laser...

Figure 13.3 General electron beam melting (PBF-EB/M/(EBM)) process scheme (own...

Figure 13.4 General binder jetting process scheme (own source).

Figure 13.5 General fused deposition modeling (FDM/MEX) process scheme (own so...

Figure 13.6 General laser direct metal deposition (LDMD) process scheme.

Figure 13.7 General laser-induced forward transfer (LIFT) process scheme.

Figure 13.8 General scheme of ultrasonic additive manufacturing [94]. Permissi...

Figure 13.9 General scheme of friction stir additive manufacturing [101]. Perm...

Figure 13.10 General scheme of aerosol jet process [110]. Permission granted f...

Figure 13.11 General scheme of liquid metal jetting process [116]. Permission ...

Figure 13.12 General scheme of nanoparticle inkjet printing process [125]. Per...

Figure 13.13 General scheme of described AM technologies—key information (own ...

Figure 13.14 The criteria of selection appropriate AM technology. Based on [13...

Chapter 14

Figure 14.1 Formation of metal matrix composites.

Figure 14.2 (a) Metal matrix composites powder and bulk manufacturing methods....

Figure 14.3 The figure shows the primary mode of operation of SLS.

Figure 14.4 Schematics of direct metal laser melting process printing in Aeros...

Figure 14.5 Electron Beam Melting (EBM) process.

Figure 14.6 Schematic of BJP 3D printing process.

Figure 14.7 Direct energy deposition process to produce LMMCs.

Figure 14.8 According to sources “GE Aviation celebrates 30,000th 3D printed f...

Figure 14.9 3D printed Ti frames of a satellite (“Aerospace 3D printing Applic...

Figure 14.10 (a) Normal hip joint morphology and hip implant, (b) Internal pla...

Figure 14.11 (a) 3D-printed circuit board, (b) UAV antenna part.

Chapter 15

Figure 15.1 IPO relationship for SC configuration adopted from [70].

Figure 15.2 Constructed a matrix of traditional manufacturing with AM supply c...

Figure 15.3 Supply chain process adopting AM in spare parts management accesse...

Figure 15.4 Illustrates a condensed representation of the prevailing supply ch...

Figure 15.5 Summarized schema of parts distribution SCM for automotive sector,...

Figure 15.6 The aircraft supply chain structure [64].

Figure 15.7 Stock and flow diagram for AM adopted SC system [64].

Chapter 16

Figure 16.1 Multi-materials and required properties for biomedical application...

Figure 16.2 SLM 3D printing process for fabrication of multi-material implants...

Figure 16.3 Directed energy deposition additive manufacturing [22].

Figure 16.4 Principles of (a) binder jetting and (b) extrusion-based 3D printi...

Figure 16.5 Multi-material scaffold manufacturing. (a) Extrusion-based 3D prin...

Figure 16.6 Ceramic/metal multi-material 3D printing. (a) Laser power bed fusi...

Figure 16.7 3D printing of polymer-bioactive glass composite scaffolds [41].

Figure 16.8 Bioprinted fibrocartilage [43].

Figure 16.9 3D printing of multi-material meniscal scaffold [44].

Figure 16.10 Fabrication of multi-material NGC. (a) Experimental setup; (b) sy...

Figure 16.11 MN fabrication process through the multi-material vat polymerizat...

Figure 16.12 Continuous liquid interface production. (a) Fabrication steps; (b...

Figure 16.13 Multi-material microfluidic device [9].

Figure 16.14 Fabrication of MCs. (I) Coprinting mechanism of liquid and solid....

Figure 16.15 3D bioprinting of multicell scaffolds [53].

Figure 16.16 Coaxial 3D bioprinting of vascular tubes. (a) Cross-linking of al...

Chapter 17

Figure 17.1 Schematic representation of DLP-based bioprinting [15].

Figure 17.2 Overview of the selection criteria for photocurable materials used...

Figure 17.3 Penetration of photons at different wavelength [52].

Figure 17.4 The fabrication process of the PR-gel [75].

Figure 17.5 Different design features for the nerve guide conduits (a), and bi...

Figure 17.6 DLP printing of contact lens [80].

Figure 17.7 (a) Injection of hydrogel onto the wound. (b) Slit-lamp images of ...

Figure 17.8 (a) Ink composition; (b) DLP-based 3D printing process followed by...

Figure 17.9 DLP printing of polymer vascular stents. (a) Computer-aided design...

Figure 17.10 DLP 3D printing of wound specific dressings [97].

Figure 17.11 DLP printing of microneedles [103].

Figure 17.12 Illustration of motion sensing capabilities of the PR hydrogel [7...

Chapter 18

Figure 18.1 Present and futuristic healthcare applications of the organ-on-a-c...

Figure 18.2 Progress in the fabrication methods in the development of microflu...

Figure 18.3 (i) Classification of 3D printing methods to fabricate the microfl...

Figure 18.4 Digital light processing (DLP)–based 3D printing: Modular approach...

Figure 18.5 3D vascularized proximal tubule on a chip (3D VaPT) model (i) extr...

Figure 18.6 (a) 3D bioprinting process of liver organ-on-a-chip platforms and ...

Figure 18.7 Detailed evolution of organ-on-a-chip models from 2007 to 2022 [56...

Figure 18.8 (i) General approaches for the

in vitro

models of the liver [70], ...

Figure 18.9 Lung on-chip micro device. (a) Compartment model with flat membran...

Figure 18.10 MFD platform for the neurovascular unit including blood-brain bar...

Figure 18.11 Schematic representation of a layered microfluidic kidney chip [9...

Figure 18.12 (a) Schematic representation of human gut-on-a-chip (GOC) model, ...

Figure 18.13 (i) Skin-on-a-chip model composed with two polyester membranes an...

Figure 18.14 Advances in organ-on-a-chip systems for modeling joint tissue and...

Figure 18.15 Arroaches for developing the multi-organs on a chip. (a) Capillar...

Chapter 19

Figure 19.1 Various stimuli-responsive/smart hydrogels [38].

Figure 19.2 (a) Preparation of silk fibroin-laponite nanocomposite hydrogels, ...

Figure 19.3 (a) Schematic illustration of glucose injectable hydrogels for ins...

Figure 19.4 Different kinds of chain growth polymerization techniques [41].

Figure 19.5 Schematic representation of the bulk, solution, suspension, and em...

Figure 19.6 Schematic illustration of dynamic hydrogels loaded with salvianoli...

Figure 19.7 Schematic representation of neural system, degeneration of nerves,...

Figure 19.8 Polyether-ether-ketone (PEEK) scaffolds using three-dimensional pr...

Figure 19.9 (a) Human eyeball with the anatomical structure of different layer...

Figure 19.10 Chemical and physical cross-linking of HA and EPL through Schiff’...

Guide

Cover Page

Table of Contents

Series Page

Title Page

Copyright Page

Preface

Begin Reading

Index

WILEY END USER LICENSE AGREEMENT

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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106

Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])

Metal Additive Manufacturing

Principles, Techniques and Applications

Edited by

R. Rajasekar

Dept. of Mechanical Engineering, Kongu Engineering College, Tamil Nadu State, India

Amir Mostafaei

Department of Mechanical, Materials and Aerospace Engineering Illinois Institute of Technology, Chicago

C. Mogana Priya

School of Mechanical Engineering, Vellore Institute of Technology, Chennai, India

and

P. Sathish Kumar

Academic Enhancement Department, King Mongkut’s University of Technology North Bangkok, Bangkok, Thailand

This edition first published 2025 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2025 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.

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Library of Congress Cataloging-in-Publication Data

ISBN 978-1-394-28762-8

Front cover image courtesy of Wikimedia CommonsCover design by Russell Richardson

Preface

At the forefront of Metal Additive Manufacturing (Metal AM), innovation meets precision to reshape the future of manufacturing. This book embarks on a journey through the transformative landscape of metal AM, a technology that has not only revolutionized rapid prototyping but also paved the way for producing high-value components from intricate materials. In this comprehensive guide, we delve deep into the intricate world of metal AM.

The structure of this book is designed to be both informative and practical. We start by exploring the foundations of metal AM, including its various technologies and the fundamental principles governing material design and extrusion. Looking forward, this book also examines future trends and advancements in metal AM. From the integration of artificial intelligence to the innovation of cold spray additive manufacturing and on-machine measurement techniques, we illuminate the future directions of this dynamic field.

Finally, we bring metal AM to life through its real-world applications across diverse sectors. Whether in aerospace, the automotive industry, healthcare, or beyond, the impact of metal AM is profound, revolutionizing production capabilities and pushing the boundaries of what is possible. With a multidisciplinary approach and practical insights drawn from leading experts in the field, this book aims to empower engineers, researchers, and professionals to harness the full transformative potential of metal AM. As the manufacturing landscape continues to evolve, we invite you to join us on this exciting journey into the intricate world of Metal Additive Manufacturing.

We offer our sincere thanks to Martin Scrivener and the Scrivener publishing team for their help with this book.

R. Rajasekar

Amir Mostafaei

C. Moganapriya

P. Sathish Kumar

1Technologies for Additive Manufacturing of Metals and Their Classification

Bhuvanesh Kumar M.1*, Justus Panicker C. T.2 and Arivazhagan D.1

1Department of Mechanical Engineering, Kongu Engineering College, Erode, India

2Department of Production Engineering, National Institute of Technology, Tiruchirappalli, India

Abstract

Additive manufacturing is a process of depositing materials in a layer-by-layer fashion, which eliminates the complexity associated with design, manufacturing, and post processing activities. Over the past years, the technology for Metal Additive Manufacturing Process (MAMP) has achieved significant advancements and developments in understanding the parameters that influence the quality of manufactured parts. The MAMP uses different forms of input materials and varying deposition rates, producing different characteristics of printed parts. Despite the wide range of sources available to gain deeper knowledge about the relationship between process parameters and resulting part characteristics, a comprehensive understanding requires a basic knowledge of the field. This chapter provides a concise classification of various MAMPs available, along with their principles of operation, operating parameters, resulting part quality, and associated applications.

Keywords: Metal additive manufacturing process (MAMP), directed energy deposition (DED), powder bed fusion (PBF), selective laser melting (SLM), wire arc additive manufacturing (WAAM), cold metal transfer (CMT)

1.1 Introduction

Additive manufacturing is a transformative process that constructs objects layer by layer from a digital model. It enables the production of intricate designs and complex structures that traditional manufacturing methods struggle to achieve. With benefits like design freedom, reduced material waste, and faster production, additive manufacturing is revolutionizing the aerospace, automotive, and healthcare industries. It has the potential to streamline supply chains by enabling on-demand and decentralized production. While conventional manufacturing processes, like computer numerical control, are still better suited for mass production of less complex parts, Metal Additive Manufacturing Processes (MAMP) are growing rapidly due to their ability to create complex parts at ease and a higher level of control. Several technologies exist for metal additive manufacturing, each with unique characteristics and capabilities. The classification of metal additive manufacturing technologies is based on the specific process employed, the energy source utilized, and the way the metal material is deposited and solidified. Standard techniques include Powder Bed Fusion (PBF) methods like Selective Laser Melting (SLM) and Electron Beam Melting (EBM), as well as Directed Energy Deposition (DED) and Binder Jetting. Ongoing advancements in speed, precision, and material compatibility continue to expand the applications and potential of metal additive manufacturing.

One of the most remarkable advantages of metal additive manufacturing lies in its ability to construct highly complex geometries that traditional manufacturing methods struggle to achieve. It is possible to design intricate lattice structures, incorporate internal channels, and optimize designs by incrementally building layers, enhancing performance while minimizing weight. Metal additive manufacturing also boasts significant benefits such as reduced material waste, shorter production lead times, and improved design flexibility. By utilizing only the necessary amount of material and eliminating the need for multiple tooling setups, it substantially curtails material costs. Additionally, the technology enables swift prototyping and on-demand production, facilitating accelerated product development cycles and customization. However, it is important to acknowledge the challenges inherent in metal additive manufacturing. The process can be time-consuming, especially for large parts, and the quality of the final output can be influenced by factors such as powder quality, process parameters, and post-processing requirements. Furthermore, the initial investment cost for metal additive manufacturing equipment is substantial, and skilled operators are essential for its operation.

Despite these challenges, metal additive manufacturing has gained remarkable traction in diverse industries, including aerospace, automotive, healthcare, and tooling. Its capacity to fabricate lightweight, intricate, and tailor-made metal components with elevated performance characteristics positions it as a transformative manufacturing technology for future applications. As research and development continue to push the boundaries of metal 3D printing, these technologies will play a vital role in shaping the future of manufacturing and unlocking innovative applications across various sectors.

1.2 Metal Additive Manufacturing Process (MAMP)

The metal additive manufacturing process consists of sequential step common to all other additive manufacturing processes:

Digital Design: The process begins with the creation of a digital 3D model of the desired metal object using Computer-Aided Design (CAD) software. This digital model serves as the blueprint for the additive manufacturing process.

Slicing: The digital model is sliced into thin cross-sectional layers using specialized software. Each layer represents a specific height or thickness that the metal object will be built upon during the additive manufacturing process. If material has overhanging structures at the risk of collapsing and difficult to print, it is recommended to add support structures to the material before slicing.

Material Preparation: The appropriate metal material and its form for the specific additive manufacturing technology is selected. This can include metal powders, metal filaments, or other forms of metal feedstock. The metal material may be pre-treated or prepared to optimize its properties for the printing process.

Printing Process: The metal additive manufacturing machine, such as a 3D printer, receives the sliced digital model and starts the printing process. The working nature of the printing would depend on the technology being employed. For example, consider the two commonly used techniques in metal additive manufacturing.

Powder Bed Fusion (PBF): In PBF, a thin layer of metal powder is evenly spread across a build platform. A high-energy source, such as a laser or electron beam, selectively scans the surface of the powder bed according to the specific layer’s design. The heat from the energy source melts and fuses the metal particles together, solidifying the layer. The build platform then moves down by one layer thickness, and the process is repeated for each subsequent layer until the entire object is complete

[1]

.

Directed Energy Deposition (DED): In DED, a focused energy source, typically a laser or electron beam, is used to melt a metal wire or powder as it is precisely deposited onto a substrate or previous layers. The energy source melts the material, which bonds with the substrate or previous layers, building up the object layer by layer.

Cooling and Solidification: As each layer is deposited and fused, it cools and solidifies to form a solid part. Cooling can occur naturally or may be aided by cooling systems within the additive manufacturing machine. Proper cooling and solidification are essential to ensuring the structural integrity and dimensional accuracy of the final metal object.

Post-Processing: Once the metal object is fully printed, it may undergo post-processing steps to improve its properties or aesthetics. Post-processing can include removing support structures if they were used during printing, heat treatment to enhance material properties, machining or surface finishing for desired surface quality, and any other required treatments based on the specific application requirements. The complete steps of MAMP are shown in

Figure 1.1

.

Figure 1.1 Metal additive manufacturing process [2].

1.3 Classification of MAMP Based on Technologies

The primary principle behind most metal additive manufacturing processes is to have a source of supply of the metal feedstock, which is then completed or partially melted and deposited on a build platform to obtain the required geometry. The variations among these processes can be understood by considering the type of metal feedstock, which can be wire, powder, solid, or liquid, and the method used to convert this raw material to the final shape. Figure 1.2 outlines the techniques of metal additive manufacturing [3].

The metal printing technique can be of liquid-based, where liquid metal droplets are deposited over each other to print the material [4]; solid-based, where solid sheets of metal, tailored to meet the required layer specification, are fused together by an external source [5]; or wire-based, where the raw material is in the form of a wire that is selectively melted and deposited over the build substrate to obtain the required geometry [6]. The technique can also be powder-based, where powder is selectively fused at a required place by using a particular source that creates ample adhesion between the powders [7].

1.4 Liquid-Based MAMP: Liquid Metal 3D Printing

The primary principle of liquid-based metal printing is that the raw material in the form of a wire is brought into a ceramic nozzle, which acts as a heater where the filler wire is melted to form a melt pool. The nozzle is surrounded by an electromagnetic coil that is pulsed to produce a varying magnetic field, causing a repercussion in the liquid metal. This induces an electric field, which creates a circulating current density and creates a circulating magnetohydrodynamic Lorentz force. The radial component of this force causes the liquid metal to eject out of the orifice, which is deposited on the build platform, as shown in Figure 1.3. This process is continued over different layers to create the final dimensions [8].

Unlike traditional metal 3D printing, which uses powdered metal, liquid metal printing operates with metals in a liquid state. The process begins with the preparation of low melting point metal alloys, such as gallium-based or eutectic alloys, which remain liquid at or near room temperature. The liquid metal is then extruded or deposited through a fine nozzle or extrusion system onto a build platform or substrate, following a computer-controlled 3D model. Upon contact with the substrate or surrounding environment, the liquid metal rapidly cools and solidifies, bonding the deposited layers together. Post-processing steps may be required to remove support structures, refine surface finishes, and enhance mechanical properties. Liquid metal 3D printing offers advantages such as high geometric complexity, fast printing speeds, and the ability to print at room temperature without additional heating or sintering processes [9]. Ongoing research aims to address challenges in flow control, viscosity, and layer adhesion to further improve the reliability and scalability of liquid metal 3D printing for applications in electronics, soft robotics, and flexible devices.

Figure 1.2 Flow chart of various additive manufacturing techniques.

Figure 1.3 Working principle of liquid-based printing [8].

1.5 Solid-Based MAMP: Ultrasonic Additive Manufacturing

In solid based metal printing, the underlying principle is stacking thin layers of metal sheets over each other in such a manner that akin to the final geometry of the part that needs to be built over a substrate and fusing them to form a required geometry. These layers are then fused to form the required geometry using various techniques. The classifications within this technique are based on the source of fusing. If an ultrasonic sonotrode is used, it is termed Ultrasonic Additive Manufacturing (a schematic is shown in Figure 1.4). If a laser and boning is used for cutting each layer and multiple layers are attached using diffusion welding or high-temperature brazing, the technique is termed as Laminated Object Manufacturing [5].

Ultrasonic additive manufacturing (UAM) is a specific type of additive manufacturing process that utilizes ultrasonic energy to create solid metal parts layer by layer [11]. It is a solid-state joining process that operates at relatively low temperatures, allowing for the bonding of metals without reaching their melting points. The working of the UAM process is detailed as follow:

Layer deposition: The UAM process begins with the deposition of thin metal foils or sheets, typically approximately 0.1 to 0.2 mm thick. These sheets are placed on top of each other layer by layer to build up the desired part geometry. The sheets are usually made of the same material, but UAM also supports the joining of dissimilar metals.

Ultrasonic welding: Once a layer is placed, ultrasonic energy is applied to the interface between the previously deposited layer and the new layer. An ultrasonic welding horn, typically made of titanium, is brought into contact with the workpiece surface. The horn generates high-frequency vibrations (typically approximately 20 kHz) that propagate through the metal sheets.

Localized heating and plastic deformation: The ultrasonic vibrations induce localized heating and plastic deformation at the interface between the sheets. The combination of pressure, vibration, and friction causes the metal atoms to diffuse across the interface, creating metallurgical bonds known as solid-state welds. These welds form between the atomically clean metal surfaces without the need for additional materials like adhesives or filler metals.

Layer compaction: The ultrasonic vibrations also induce a phenomenon called “metal compaction.” The vibrating horn exerts downward pressure on the workpiece, ensuring intimate contact between the layers. This compaction helps to eliminate voids, porosity, and other defects that could compromise the structural integrity of the part.

CNC control and motion system: UAM employs a Computer Numerical Control (CNC) system to precisely control the position and movement of the ultrasonic welding horn and the workpiece. This CNC control allows for accurate layer-by-layer deposition and the creation of complex geometries.

Build plate movement: As each layer is deposited and bonded, the build plate holding the workpiece moves downward (or the horn moves upward) to create space for the next layer. This vertical movement is essential to maintain the proper distance between the horn and the work piece and to facilitate the continuous build process.

Post-processing and finishing: After the completion of the additive manufacturing process, the UAM parts may undergo post-processing operations, such as machining, heat treatment, or surface finishing, to achieve the desired final dimensions, properties, and aesthetics.

Figure 1.4 Working principle of ultrasonic additive manufacturing [10].

1.6 Powder-Based MAMP

In powder-based additive manufacturing, the powder is primarily fused together by specific means, and the classification among these processes arises from the differences in the source and the methodology of fusing the particles together. The heat source can be from a laser or an electron beam, which irradiates, melts, and fuses the pre-laid and/or intermediately laid powdered particles with the aid of a powder roller from a powder delivery system, properly indexed to form the final geometry. If the heat source from a laser is used to sinter and join the powder particles, the process is called Selective Laser Sintering (SLS). On the other hand, if there is a complete melting of the powder, the process is called Selective Laser Melting (SLM) or Direct Metal Laser Sintering (DMLS). If the heat source is from an electron beam, the process is termed Electron Beam Melting (EBM) [12].

1.6.1 Binder Jetting

Binder jetting is a process in which a print head selectively deposits a binder material onto a powder bed, bonding together the areas that need to be an integral part of the final geometry. This process is repeated for every layer, and these layers combine to the final geometry. As the jetting of a particular layer is completed, the table is indexed, and the process repeats [13]. Generally, this process is accomplished by post-processing, possibly sintering, to strengthen the bonding between adjacent powders. Infiltration can also be performed to reinforce the required properties, as shown in Figure 1.5.

1.6.2 Powder Direct Energy Deposition (DED)

Direct energy deposition is a process of additive manufacturing that primarily uses a concentrated source of energy to melt the material being conveyed onto the energy focus. If the feed material is in the form of powder, the methodology would be classified as powder-based additive manufacturing. If the feed is in the form of wire, the techniques would come under wire-based additive manufacturing. Most powder-based techniques use a laser as an energy source, where powders are fed towards the laser’s energy focus. The heat source melts the powders and deposits them onto the substrate, as shown in Figure 1.6.

1.6.2.1 Laser Cladding Technology

Laser Cladding (LC) is a broad, interdisciplinary technique incorporating laser processing, Computer-Aided Design and Manufacturing (CAD/CAM), digital control, and powder metallurgy [15]. The quality of the final coating is significantly impacted by the various processing techniques used in the LC process. There are four different LC techniques: wire feeding [16], off-axis powder feeding [17], pre-placed powder [18], and coaxial powder feeding [19]. The cladding material is delivered directly to the laser beam during the coaxial powder feeding process, which is completed simultaneously with the use of shielding gas, as shown in Figure 1.7(a). In the first step of the pre-placed powder method, the cladding material must be pre-placed on the work piece’s surface, as shown in Figure 1.7(b). The second stage involves melting the materials while they are exposed to laser light. In the off-axis powder feeding system, shown in Figure 1.7(c), The powder is given directly to the workpiece, and there is a predetermined distance between the powder feeding tube and the laser beam axis. A wire feeding system, shown in Figure 1.7(d), replaces the powder with a wire approximately 1 mm in diameter. The qualities of the coating are significantly affected by the density, thickness, and homogeneity of the pre-placed powder technique. To prevent the powder materials from being blown away by the shielding gas, the chosen binders must dry quickly while maintaining the compact condition. Additionally, altered processing directions in the off-axis powder feeding and wire feeding systems impact the quantity of powder fed and reduced processing accuracy, severely restricting their capacity for multi-dimensional formation. In contrast, the coaxial powder feeding process is more steady and precise than other approaches because there is no direct contact with the melt pool, and the laser beam is not attenuated by powder particles, as illustrated in Figure 1.8.

Figure 1.5 Working principle of binder jetting [13].

Figure 1.6 Working principle of powder-based DED [14].

Figure 1.7 Schematic diagrams of the LC processing mode: (a) coaxial powder feeding method; (b) preplaced powder method; (c) off-axis powder feeding method; and (d) wire feeding method [20].

Figure 1.8 Schematic diagram of the LC system with the coaxial powder feeding method [20].

1.6.2.2 Underwater LC Technology

The need for undersea maintenance is growing more urgent alongside the outstanding advancements in offshore engineering. The repair and upkeep of naval equipment frequently utilize underwater arc welding technology as well as underwater laser beam welding. However, as water depth increases, the current constraints (unstable droplet transition, fixed material system, and rigid welding angle) make it increasingly difficult to establish the efficient maintenance procedures required for these techniques. Underwater LC technology is anticipated to evolve into an innovative maintenance procedure with a favorable impact on the advancement of maritime engineering as a new type of online maintenance technique [21].

A unique gas curtain nozzle is mounted on the LC head to create a local tool for producing drying cavities in an underwater environment. Depositing cladding materials involves using an LC head equipped with an annular powder feeding module. To create an underwater processing environment, the substrate is first added to the water tank, and then water is poured into the tank. The underwater production tool is then lowered to the ground and placed on top of the substrate during the process stage. Water is removed when the exhaust gas shoots out of the air curtain nozzle, creating a small dry space directly on the substrate. The LC head then transmits a laser beam and powder to complete the underwater maintenance within the adjacent dry compartment.

1.6.3 Powder Bed Fusion (PBF)

PBF involves employing a thermal heat source to melt or sinter metal particles together. There are numerous PBF varieties, and each shares the same characteristics. These include a built chamber with an inert atmosphere to prevent the molten metal from oxidizing, a thermal source for fusing metal powder particles, a device to control the fusion, and a technique for depositing and smoothing each layer of metal powder. The energy source employed in PBF systems, often a laser or electron beam, is what makes them unique. Electron beam melting processes utilize electron beams. The most common energy source, lasers, are classified as either selective laser sintering or selective laser melting depending on how they fuse metal powder particles together by either laser sintering or laser melting [22].

The PBF process is shown in Figure 1.9, which depicts the interior of an inert (nitrogen or argon gas) build chamber where thin layers of metal powder, ranging in thickness from 20 to 200 m, are evenly disseminated across a powder bed by a powder spreader [23], also known as a re-coater. Recoater bump, also known as layer deformation due to improper re-coater adjustment, must be considered at the design stage. After the first layer has been applied and dispersed, a high-powered beam is used to melt or sinter the powder particles in accordance with a tool path based on a 3D CAD model. Additionally, support structures made of the same material are constructed simultaneously to reduce any distortion caused by high temperatures during the melting or sintering phase. After scanning the first layer, the powder bed advances in the opposite direction from the previously applied layer, maintaining an equal distance, where the powder is stored and re-coater applies a second coating of loose powder. This sequence is then repeated until the segment is complete. To prevent heat shock and enable safe handling, gradual equilibrium to ambient temperature is achieved after completion. The surplus loose powder is manually removed and recycled once the part has stabilized and is removed from the powder bed. Since PBF technologies utilize unique particle fusion mechanisms, they are used to manufacture metal components through sintering and melting.

Figure 1.9 Schematic of a typical PBF machine [24].

1.6.3.1 Electron Beam PBF: Electron Beam Melting (EBM)

Figure 1.10 shows the schematic of an EBM system. The EBM system consists of an electron gun that operates at a power of 60 kW to produce a focused beam with an energy density above 100 kW/cm2. This electron gun is similar to the ones used in a scanning electron microscope or an electron beam welding machine. Electromagnetic lenses control the beam’s focus, while deflection coils regulate the beam’s movement on the build table. The table is covered with a powder layer that is 100 μm thick for manufacturing a part. Two hoppers inside the build chamber provide the powder. The powder is gathered from both sides and spread across the table by a moving rake. Before melting the powder layer according to the shape specified by the CAD file, the electron beam pre-heats the powder layer with a faster scan speed. Every layer of a part is constructed using EBM in two processes. The first step, known as contouring, involves creating the part’s outside boundary, and the second involves melting the powder inside the contour to finish one layer. This procedure is repeated until the required three-dimensional component is finished [25].

Electron beam melting has the potential to completely transform the implant production industry. The metal powder is melted using electron beam energy. The entire procedure occurs in a vacuum chamber because an electron beam is used as the energy source [26]. By providing an oxygen-free atmosphere and reducing the chance of hydrogen pick-up, the vacuum maintains high purity. This feature is especially helpful when creating parts out of titanium-6 aluminum-4 vanadium (Ti-6Al-4V) due to the ability to manage low amounts of interstitial elements during fabrication. Orthopedic components like knee, hip, and jaw replacements, as well as maxillofacial plates, have been made using EBM [27]. The United States Food and Drug Administration (FDA) has also approved EBM-produced implants, such as acetabular cups, which have been CE-certified since 2007 and 2010, respectively.

Figure 1.10 Schematic of EBM system [28].

1.6.3.2 Laser PBF: Selective Laser Sintering

The layer-additive manufacturing technique known as Selective Laser Sintering (SLS) uses powder and is typically employed for quick tooling and prototyping [29]. Laser beams in either continuous or pulsed mode are used as a heat source to scan and fuse particles into layers with preset sizes and shapes. The geometry of the scanned layers matches the various cross-sections of the Stereolithography (STL) or Computer-Aided Design (CAD) models of the product. After the initial layer of loose powder is scanned, a second layer is added on top of it, and the process is continued until the build is finished, as shown in Figure 1.11[30].

Models for design testing, patterns for investment casting, and other products have all been created using selective laser sintering. Small batches of useful components have also been produced. This technology has been employed in injection moulding [31], fast tooling for electrical discharge machining electrodes [32], polymer moulding [33], sand casting moulds [34], zirconia moulds for titanium castings, bio-medical applications [35], lead zirconate-titanate (PZT) parts, and sheet metal parts [36].

The following mechanisms are involved when laser heat energy is absorbed by materials: viscous-flow binding, curvature effect, particle wetting, solid-state sintering, liquid-phase sintering, and real melting [38]. In materials with the proper temperature-dependent viscosity, viscous-flow binding predominates, while the curvature effect drives nano-crystalline materials. The sequential steps followed in the SLS process are discussed below:

Powder Bed Preparation: A thin and uniform layer of powdered material is evenly spread across a build platform. The material used can vary depending on the desired properties and application of the final object, including polymers, metals, or ceramics.

Laser Scanning: A high-powered laser beam is precisely controlled and directed to scan the surface of the powder bed. This scanning process follows the contours of the object, guided by a digital model or design.

Selective Heating: As the laser interacts with the powdered material, it delivers intense and localized heat energy to specific areas. The heat causes the particles to reach their melting point, resulting in the fusion and solidification of adjacent particles. This selective heating process ensures the bonding of the powdered material while minimizing the risk of complete liquefaction.

Layer-by-Layer Building: Once a layer is sintered, the build platform moves down by a predetermined thickness, and a new layer of powdered material is evenly spread on top. The laser scanning and selective heating process is repeated for each layer, progressively building the object from the bottom up.

Cooling and Solidification: As each layer is sintered, the previously fused material begins to cool and solidify. This cooling phase is essential to ensure the structural integrity and dimensional stability of the object.