Post-Processing Techniques to Enhance the Quality of Metallic Parts Produced by Additive Manufacturing

Additive manufacturing (AM) processes can produce three-dimensional (3D) near-net-shape parts based on computer-aided design (CAD) models. Compared to traditional manufacturing processes, AM processes can generate parts with intricate geometries, operational flexibility and reduced manufacturing time, thus saving time and money. On the other hand, AM processes face complex issues, including poor surface finish, unwanted microstructure phases, defects, wear tracks, reduced corrosion resistance and reduced fatigue life. These problems prevent AM parts from real-time operational applications. Post-processing techniques, including laser shock peening, laser polishing, conventional machining methods and thermal processes, are usually applied to resolve these issues. These processes have proved their capability to enhance the surface characteristics and physical and mechanical properties. In this study, various post-processing techniques and their implementations have been compiled. The effect of post-processing techniques on additively manufactured parts has been discussed. It was found that laser shock peening (LSP) can cause severe strain rate generation, especially in thinner components. LSP can control the surface regularities and local grain refinement, thus elevating the hardness value. Laser polishing (LP) can reduce surface roughness up to 95% and increase hardness, collectively, compared to the as-built parts. Conventional machining processes enhance surface quality; however, their influence on hardness has not been proved yet. Thermal post-processing techniques are applied to eliminate porosity up to 99.99%, increase corrosion resistance, and finally, the mechanical properties’ elevation. For future perspectives, to prescribe a particular post-processing technique for specific defects, standardization is necessary. This study provides a detailed overview of the post-processing techniques applied to enhance the mechanical and physical properties of AM-ed parts. A particular method can be chosen based on one’s requirements.

3D Modeling of the Solidification Structure Evolution of Superalloys in Powder Bed Fusion Additive Manufacturing Processes

Recently, a few computational methodologies and algorithms have been developed to simulate the microstructure evolution in powder bed fusion (PBF) additive manufacturing (AM) processes. However, none of these have attempted to simulate the grain structure evolution in multitrack, multilayer AM components in a fully 3D transient mode and for the entire AM geometry. In this work, a multiscale model, which consists of coupling a transient, discrete-source 3D AM process model with a 3D stochastic solidification structure model, was applied to quickly, efficiently, and accurately predict the grain structure evolution of IN625 alloys during Laser Powder Bed Fusion (LPBF). The capabilities of this model include studying the effects of process parameters and part geometry on solidification conditions and their impact on the grain structure formation within multicomponent alloy parts processed via AM. Validation was accomplished based on single-layer LPBF IN625 benchmark experiments, previously performed and analyzed at the National Institute of Standards and Technology (NIST), USA. This modeling approach can also be used to quantitatively predict the solidification structure of Ti-6Al-4V alloys in electron beam AM processes.

Analysis and characterization of additive manufacturing processes

Recently, additive manufacturing (AM) processes have expanded rapidly in various fields of the industry because they offer design freedom, involve layer-by-layer construction from a computerized 3D model (minimizing material consumption), and allow the manufacture of parts with complex geometry (thus offering the possibility of producing custom parts). Also, they provide the advantage of a short time to make the final parts, do not involve the need for auxiliary resources (cutting tools, lighting fixtures or coolants) and have a low impact on the environment. However, the aspects that make these technologies not yet widely used in industry are poor surface quality of parts, uncertainty about the mechanical properties of products and low productivity. Research on the physical phenomena associated with additive manufacturing processes is necessary for proper control of the phenomena of melting, solidification, vaporization and heat transfer. This paper addresses the relevant additive manufacturing processes and their applications and analyzes the advantages and disadvantages of AM processes compared to conventional production processes. For the aerospace industry, these technologies offer possibilities for manufacturing lighter structures to reduce weight, but improvements in precision must be sought to eliminate the need for finishing processes.

Designed Deposition - Freeform 3D Printing for Digitally Crafted Artefacts

<p>Through the exploitation of new additive manufacturing (AM) processes, this research seeks to reinvent the designer as an informed mediator between the digitally defined and the physically expressed. Current 3D printing techniques generally construct an object layer by layer, building vertically in the z-axis. Recently developed, ‘freeform 3D printing’ is an AM method which builds through the deposition of material that solidifies upon extrusion. The result is free-standing material forms with diminished need for support material. Building in this spatial manner means that AM is no longer reliant on layer based techniques that are built from ground-up. Instead, motions can move simultaneously in the x, y and z axes. This increased freedom of motion allows the designer to disregard the requisite that solid forms need to be delineated prior to considering material deposition. Considering this in relationship to the design of artefacts, specific approaches that consider both form and material deposition concurrently allow the authorship of the method of making to be reclaimed. Bespoke computational processes work to encode material deposition with qualities that are tactile, visual and expressive of its making method. Considerations to structural, performative and aesthetic implications are assimilated from the onset rather than post-rationalised. Material deposition is crafted to become three-dimensionally informed and considerate of the integral nature of its making method and its output, exposing new design opportunities. Among other things, the research-through-design process suggests how parametric modelling could be used for mass-customisation and suggests a possible path for AM beyond prototyping, towards the manufacturing of bespoke products through an industrial design perspective. Through iterative abstract and application based experiments, Designed Deposition pursues an increasingly integrated process between the user, the designer, the digital and the physical, towards the creation of digitally crafted artefacts.</p>

Designed Deposition - Freeform 3D Printing for Digitally Crafted Artefacts

<p>Through the exploitation of new additive manufacturing (AM) processes, this research seeks to reinvent the designer as an informed mediator between the digitally defined and the physically expressed. Current 3D printing techniques generally construct an object layer by layer, building vertically in the z-axis. Recently developed, ‘freeform 3D printing’ is an AM method which builds through the deposition of material that solidifies upon extrusion. The result is free-standing material forms with diminished need for support material. Building in this spatial manner means that AM is no longer reliant on layer based techniques that are built from ground-up. Instead, motions can move simultaneously in the x, y and z axes. This increased freedom of motion allows the designer to disregard the requisite that solid forms need to be delineated prior to considering material deposition. Considering this in relationship to the design of artefacts, specific approaches that consider both form and material deposition concurrently allow the authorship of the method of making to be reclaimed. Bespoke computational processes work to encode material deposition with qualities that are tactile, visual and expressive of its making method. Considerations to structural, performative and aesthetic implications are assimilated from the onset rather than post-rationalised. Material deposition is crafted to become three-dimensionally informed and considerate of the integral nature of its making method and its output, exposing new design opportunities. Among other things, the research-through-design process suggests how parametric modelling could be used for mass-customisation and suggests a possible path for AM beyond prototyping, towards the manufacturing of bespoke products through an industrial design perspective. Through iterative abstract and application based experiments, Designed Deposition pursues an increasingly integrated process between the user, the designer, the digital and the physical, towards the creation of digitally crafted artefacts.</p>

Investigation of Applicability of Additive Manufacturing Processes to Appropriate Technologies for Developing Countries

In recent years, additive manufacturing (AM) processes have emerged as an important manufacturing technology for a multi-item small sized production to lead the 4th industrial revolution. The layer-by-layer deposition characteristics of AM process can rapidly produce physical parts with three-dimensional geometry and desired functionality in a relatively low cost environment. The goal of this paper is to investigate the applicability of AM process to appropriate technologies for developing countries. Through the review of examples of appropriate technology of the AM process, the possibility of a practical usage of the AM process for the appropriate technologies is examined. In addition, significant applications of the AM process to the appropriate technology are introduced. Finally, future issues related to production of physical parts for developing countries using the AM process are discussed from the viewpoint of the appropriate technology.

Additive Manufacturing of Micro-Electro-Mechanical Systems (MEMS)

Recently, additive manufacturing (AM) processes applied to the micrometer range are subjected to intense development motivated by the influence of the consolidated methods for the macroscale and by the attraction for digital design and freeform fabrication. The integration of AM with the other steps of conventional micro-electro-mechanical systems (MEMS) fabrication processes is still in progress and, furthermore, the development of dedicated design methods for this field is under development. The large variety of AM processes and materials is leading to an abundance of documentation about process attempts, setup details, and case studies. However, the fast and multi-technological development of AM methods for microstructures will require organized analysis of the specific and comparative advantages, constraints, and limitations of the processes. The goal of this paper is to provide an up-to-date overall view on the AM processes at the microscale and also to organize and disambiguate the related performances, capabilities, and resolutions.

Enabling Multi-Material Structures of Co-Based Superalloy Using Laser Directed Energy Deposition Additive Manufacturing

Cobalt superalloys such as Tribaloys are widely used in environments that involve high temperatures, corrosion, and wear degradation. Additive manufacturing (AM) processes have been investigated for fabricating Co-based alloys due to design flexibility and efficient materials usage. AM processes are suitable for reducing the manufacturing steps and subsequently reducing manufacturing costs by incorporating multi-materials. Laser directed energy deposition (laser DED) is a suitable AM process for fabricating Co-based alloys. T800 is one of the commercially available Tribaloys that is strengthened through Laves phases and of interest to diverse engineering fields. However, the high content of the Laves phase makes the alloy prone to brittle fracture. In this study, a Ni-20%Cr alloy was used to improve the fabricability of the T800 alloy via laser DED. Different mixture compositions (20%, 30%, 40% NiCr by weight) were investigated. The multi-material T800 + NiCr alloys were heat treated at two different temperatures. These alloy chemistries were characterized for their microstructural, phase, and mechanical properties in the as-fabricated and heat-treated conditions. SEM and XRD characterization indicated the stabilization of ductile phases and homogenization of the Laves phases after laser DED fabrication and heat treatment. In conclusion, the NiCr addition improved the fabricability and structural integrity of the T800 alloy.

Towards an Australian social housing best practice asset management framework

This research examines social housing asset management (AM) in Australia and develops a best practice framework that outlines AM processes and criteria for making decisions; is suitable to the unique aspects of social housing; is flexible enough to be used by different types of social housing providers; provides metrics to drive organisational excellence; and provides the basis for national regulation and policymaking.

Towards an Australian social housing best practice asset management framework

This research examines social housing asset management (AM) in Australia and develops a best practice framework that outlines AM processes and criteria for making decisions.