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Article
Publication date: 27 March 2009

S. Kumar, J.‐P. Kruth, J. Van Humbeeck and A. Voet

Surface changes like wear or local plastic deformation occurring during service of a mould make it unsuitable for further use and determine its life‐time. The performance of the…

678

Abstract

Purpose

Surface changes like wear or local plastic deformation occurring during service of a mould make it unsuitable for further use and determine its life‐time. The performance of the mould and its design are important aspects that influence its longevity. The purpose of this paper is to study the behaviour of mould materials manufactured by laser sintering, a type of rapid manufacturing process, and to explain their relative in‐service performance.

Design/methodology/approach

Mould specimens were made by two laser‐sintering machines (a DTM Sinterstation and an EOSint M250 Xtended equipped with CO2 lasers) using two iron‐based commercial powders, i.e. LaserForm ST‐100 and DirectSteel 20 V1, respectively. They have been subjected to two types of wear tests, i.e. bidirectional fretting and unidirectional pin‐on‐disc tests, under loading conditions leading to wear and/or plastic deformation of the specimens. The results obtained show similar trends to that obtained from the real‐life performance of polymer injection moulds manufactured using such materials and processes.

Findings

LaserForm is a better material for injection moulds material than DirectSteel; however, and its performance will deteriorate under impact injection moulding conditions where plastic surface deformation will occur in addition to abrasive wear. Both materials show high coefficient of friction, their performance will be enhanced by redesigning the composition of the powders by incorporating hard and low friction components. The methodology adopted here for investigating the surface degradation behaviours of materials is able to give sufficient and reliable information about the wear behaviour of mould materials for practical applications.

Originality/value

It is concluded that the wear tests used here are suited to characterize the in‐service mould wear strength, and such tests could be preferably used to shorten the mould development/validation time.

Details

Rapid Prototyping Journal, vol. 15 no. 2
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 16 November 2021

Kai-Uwe Garthe, Kay-Peter Hoyer, Leif Hagen, Wolfgang Tillmann and Mirko Schaper

The currently existing restrictions regarding the deployment of additively manufactured components because of poor surface roughness, porosity and residual stresses as well as…

252

Abstract

Purpose

The currently existing restrictions regarding the deployment of additively manufactured components because of poor surface roughness, porosity and residual stresses as well as their influence on the low-cycle fatigue (LCF) strength are addressed in this paper.

Design/methodology/approach

This study aims to evaluating the effect of different pre- and post-treatments on the LCF strength of additively manufactured 316L parts. Therefore, 316L specimens manufactured by laser powder bed fusion were examined in their as-built state as well as after grinding, or coating with regard to the surface roughness, residual stresses and LCF strength. To differentiate between topographical effects and residual stress-related phenomena, stress-relieved 316L specimens served as a reference throughout the investigations. To enable an alumina coating of the 316L components, atmospheric plasma spraying was used, and the near-surface residual stresses and the surface roughness are measured and investigated.

Findings

The results have shown that the applied pre- and post-treatments such as stress-relief heat treatment, grinding and alumina coating have each led to an increase in LCF strength of the 316L specimens. In contrast, the non-heat-treated specimens predominantly exhibited coating delamination.

Originality/value

To the best of the authors’ knowledge, this is the first study of the correlation between the LCF behavior of additively manufactured uncoated 316L specimens in comparison with additively manufactured 316L specimens with an alumina coating.

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Article
Publication date: 6 September 2022

Agnieszka Chmielewska, Bartlomiej Adam Wysocki, Elżbieta Gadalińska, Eric MacDonald, Bogusława Adamczyk-Cieślak, David Dean and Wojciech Świeszkowski

The purpose of this paper is to investigate the effect of remelting each layer on the homogeneity of nickel-titanium (NiTi) parts fabricated from elemental nickel and titanium…

1907

Abstract

Purpose

The purpose of this paper is to investigate the effect of remelting each layer on the homogeneity of nickel-titanium (NiTi) parts fabricated from elemental nickel and titanium powders using laser powder bed fusion (LPBF). In addition, the influence of manufacturing parameters and different melting strategies, including multiple cycles of remelting, on printability and macro defects, such as pore and crack formation, have been investigated.

Design/methodology/approach

An LPBF process was used to manufacture NiTi alloy from elementally blended powders and was evaluated with the use of a remelting scanning strategy to improve the homogeneity of fabricated specimens. Furthermore, both single melt and up to two remeltings were used.

Findings

The results indicate that remelting can be beneficial for density improvement as well as chemical and phase composition homogenization. Backscattered electron mode in scanning electron microscope showed a reduction in the presence of unmixed Ni and Ti elemental powders in response to increasing the number of remelts. The microhardness values of NiTi parts for the different numbers of melts studied were similar and ranged from 487 to 495 HV. Nevertheless, it was observed that measurement error decreases as the number of remelts increases, suggesting an increase in chemical and phase composition homogeneity. However, X-ray diffraction analysis revealed the presence of multiple phases regardless of the number of melt runs.

Originality/value

For the first time, to the best of the authors’ knowledge, elementally blended NiTi powders were fabricated via LPBF using remelting scanning strategies.

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Article
Publication date: 23 August 2021

Iván La Fé-Perdomo, Jorge Andres Ramos-Grez, Gerardo Beruvides and Rafael Alberto Mujica

The purpose of this paper is to outline some key aspects such as material systems used, phenomenological and statistical process modeling, techniques applied to monitor the…

718

Abstract

Purpose

The purpose of this paper is to outline some key aspects such as material systems used, phenomenological and statistical process modeling, techniques applied to monitor the process and optimization approaches reported. All these need to be taken into account for the ongoing development of the SLM technique, particularly in health care applications. The outcomes from this review allow not only to summarize the main features of the process but also to collect a considerable amount of investigation effort so far achieved by the researcher community.

Design/methodology/approach

This paper reviews four significant areas of the selective laser melting (SLM) process of metallic systems within the scope of medical devices as follows: established and novel materials used, process modeling, process tracking and quality evaluation, and finally, the attempts for optimizing some process features such as surface roughness, porosity and mechanical properties. All the consulted literature has been highly detailed and discussed to understand the current and existing research gaps.

Findings

With this review, there is a prevailing need for further investigation on copper alloys, particularly when conformal cooling, antibacterial and antiviral properties are sought after. Moreover, artificial intelligence techniques for modeling and optimizing the SLM process parameters are still at a poor application level in this field. Furthermore, plenty of research work needs to be done to improve the existent online monitoring techniques.

Research limitations/implications

This review is limited only to the materials, models, monitoring methods, and optimization approaches reported on the SLM process for metallic systems, particularly those found in the health care arena.

Practical implications

SLM is a widely used metal additive manufacturing process due to the possibility of elaborating complex and customized tridimensional parts or components. It is corroborated that SLM produces minimal amounts of waste and enables optimal designs that allow considerable environmental advantages and promotes sustainability.

Social implications

The key perspectives about the applications of novel materials in the field of medicine are proposed.

Originality/value

The investigations about SLM contain an increasing amount of knowledge, motivated by the growing interest of the scientific community in this relatively young manufacturing process. This study can be seen as a compilation of relevant researches and findings in the field of the metal printing process.

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Article
Publication date: 20 March 2017

Gonzalo Reyes Donoso, Magdalena Walczak, Esteban Ramos Moore and Jorge Andres Ramos-Grez

The purpose of this paper is to explore the possibility of producing Cu-based shape memory alloys (SMA) by means of direct metal laser fabrication (DMLF).

441

Abstract

Purpose

The purpose of this paper is to explore the possibility of producing Cu-based shape memory alloys (SMA) by means of direct metal laser fabrication (DMLF).

Design/methodology/approach

The fabrication approach consists of the combination of laser melting of a metallic powder with heating treatment in a controlled inert atmosphere. Three prospective Cu-Al-Ni alloy compositions were tested, and the effects of laser power, as well as laser exposure time, were verified.

Findings

All the processed materials were found to attain microstructures and phase change transformation temperatures typical of this type of SMA.

Practical implications

Further development of this technique will allow for fabrication of large elements with considerable shape memory effect, which are currently not viable due to high cost of nitinol.

Originality/value

This work showed a proof of concept toward the development of DMLF-based additive manufacturing of near net shape components of Cu-based SMAs from elemental powders.

Details

Rapid Prototyping Journal, vol. 23 no. 2
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 2 February 2023

Mahyar Khorasani, Ian Gibson, Amir Hossein Ghasemi, Elahe Hadavi and Bernard Rolfe

The purpose of this study is, to compare laser-based additive manufacturing and subtractive methods. Laser-based manufacturing is a widely used, noncontact, advanced manufacturing…

1390

Abstract

Purpose

The purpose of this study is, to compare laser-based additive manufacturing and subtractive methods. Laser-based manufacturing is a widely used, noncontact, advanced manufacturing technique, which can be applied to a very wide range of materials, with particular emphasis on metals. In this paper, the governing principles of both laser-based subtractive of metals (LB-SM) and laser-based powder bed fusion (LB-PBF) of metallic materials are discussed and evaluated in terms of performance and capabilities. Using the principles of both laser-based methods, some new potential hybrid additive manufacturing options are discussed.

Design methodology approach

Production characteristics, such as surface quality, dimensional accuracy, material range, mechanical properties and applications, are reviewed and discussed. The process parameters for both LB-PBF and LB-SM were identified, and different factors that caused defects in both processes are explored. Advantages, disadvantages and limitations are explained and analyzed to shed light on the process selection for both additive and subtractive processes.

Findings

The performance of subtractive and additive processes is highly related to the material properties, such as diffusivity, reflectivity, thermal conductivity as well as laser parameters. LB-PBF has more influential factors affecting the quality of produced parts and is a more complex process. Both LB-SM and LB-PBF are flexible manufacturing methods that can be applied to a wide range of materials; however, they both suffer from low energy efficiency and production rate. These may be useful when producing highly innovative parts detailed, hollow products, such as medical implants.

Originality value

This paper reviews the literature for both LB-PBF and LB-SM; nevertheless, the main contributions of this paper are twofold. To the best of the authors’ knowledge, this paper is one of the first to discuss the effect of the production process (both additive and subtractive) on the quality of the produced components. Also, some options for the hybrid capability of both LB-PBF and LB-SM are suggested to produce complex components with the desired macro- and microscale features.

Details

Rapid Prototyping Journal, vol. 29 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 6 August 2019

Sahil Dhiman, Sarabjeet Singh Sidhu, Preetkanwal Singh Bains and Marjan Bahraminasab

With technology advances, metallic implants claim to improve the quality and durability of human life. In the recent decade, Ti-6Al-4V biomaterial has been additively manufactured…

695

Abstract

Purpose

With technology advances, metallic implants claim to improve the quality and durability of human life. In the recent decade, Ti-6Al-4V biomaterial has been additively manufactured via selective laser melting (SLM) for orthopedic applications. This paper aims to provide state-of-the-art on mechanobiology of these fabricated components.

Design/methodology/approach

A literature review has been done to explore the potential of SLM fabricated Ti-6Al-4V porous lattice structures (LS) as bone substitutes. The emphasize was on the effect of process parameters and porosity on mechanical and biological properties. The papers published since 2007 were considered here. The keywords used to search were porous Ti-6Al-4V, additive manufacturing, metal three-dimensional printing, osseointegration, porous LS, SLM, in vitro and in vivo.

Findings

The properties of SLM porous biomaterials were compared with different human bones, and bulk SLM fabricated Ti-6Al-4V structures. The comparison was also made between LS with different unit cells to find out whether there is any particular design that can mimic the human bone functionality and enhance osseointegration.

Originality/value

The implant porosity plays a crucial role in mechanical and biological characteristics that relies on the optimum controlled process variables and design attributes. It was also indicated that although the mechanical strength (compressive and fatigue) of porous LS is not mostly close to natural cortical bone, elastic modulus can be adjusted to match that of cortical or cancellous bone. Porous Ti-6Al-4V provide favorable bone formation. However, the effect of design variables on biological behavior cannot be fully conclusive as few studies have been dedicated to this.

Details

Rapid Prototyping Journal, vol. 25 no. 7
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 17 October 2017

Karl P. Davidson and Sarat B. Singamneni

This paper aims to establish the microstructures and the process-structure relationships in duplex stainless steel powders consolidated by selective laser melting (SLM).

738

Abstract

Purpose

This paper aims to establish the microstructures and the process-structure relationships in duplex stainless steel powders consolidated by selective laser melting (SLM).

Design/methodology/approach

A priori data on energy density levels most appropriate to consolidation of duplex stainless steel powders through SLM served as the basis to converge on the laser settings. Experimental designs with varying laser power and scan speeds and test pieces generated allowed metallographic evaluations based on optical and scanning electron microscopy and electro backscatter diffraction analyses.

Findings

Duplex stainless steel powders are established for processing by SLM. However, the dynamic point heat source and associated transient thermal fields affect the microstructures to be predominantly ferritic, with grains elongated in the build direction. Austenite precipitated either at the grain boundaries or as Widmanstätten laths, whereas the crystallographic orientations and the grain growth are affected around the cavities. Considerable CrN precipitation is also evidenced.

Originality/value

Duplex stainless steels are relatively new candidates to be brought into the additive manufacturing realm. Considering the poor machinability and other difficulties, the overarching result indicating suitability of duplex powders by SLM is of considerable value to the industry. More significantly, the metallographic evaluation and results of the current research allowed further understanding of the material consolidation aspects and pave ways for fine tuning and establishment of the process-structure-property relationships for this important process-material combination.

Details

Rapid Prototyping Journal, vol. 23 no. 6
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 3 February 2023

Arad Azizi, Fatemeh Hejripour, Jacob A. Goodman, Piyush A. Kulkarni, Xiaobo Chen, Guangwen Zhou and Scott N. Schiffres

AlSi10Mg alloy is commonly used in laser powder bed fusion due to its printability, relatively high thermal conductivity, low density and good mechanical properties. However, the…

491

Abstract

Purpose

AlSi10Mg alloy is commonly used in laser powder bed fusion due to its printability, relatively high thermal conductivity, low density and good mechanical properties. However, the thermal conductivity of as-built materials as a function of processing (energy density, laser power, laser scanning speed, support structure) and build orientation, are not well explored in the literature. This study aims to elucidate the relationship between processing, microstructure, and thermal conductivity.

Design/methodology/approach

The thermal conductivity of laser powder bed fusion (L-PBF) AlSi10Mg samples are investigated by the flash diffusivity and frequency domain thermoreflectance (FDTR) techniques. Thermal conductivities are linked to the microstructure of L-PBF AlSi10Mg, which changes with processing conditions. The through-plane exceeded the in-plane thermal conductivity for all energy densities. A co-located thermal conductivity map by frequency domain thermoreflectance (FDTR) and crystallographic grain orientation map by electron backscattered diffraction (EBSD) was used to investigate the effect of microstructure on thermal conductivity.

Findings

The highest through-plane thermal conductivity (136 ± 2 W/m-K) was achieved at 59 J/mm3 and exceeded the values reported previously. The in-plane thermal conductivity peaked at 117 ± 2 W/m-K at 50 J/mm3. The trend of thermal conductivity reducing with energy density at similar porosity was primarily due to the reduced grain size producing more Al-Si interfaces that pose thermal resistance. At these interfaces, thermal energy must convert from electrons in the aluminum to phonons in the silicon. The co-located thermal conductivity and crystallographic grain orientation maps confirmed that larger colonies of columnar grains have higher thermal conductivity compared to smaller columnar grains.

Practical implications

The thermal properties of AlSi10Mg are crucial to heat transfer applications including additively manufactured heatsinks, cold plates, vapor chambers, heat pipes, enclosures and heat exchangers. Additionally, thermal-based nondestructive testing methods require these properties for applications such as defect detection and simulation of L-PBF processes. Industrial standards for L-PBF processes and components can use the data for thermal applications.

Originality/value

To the best of the authors’ knowledge, this paper is the first to make coupled thermal conductivity maps that were matched to microstructure for L-PBF AlSi10Mg aluminum alloy. This was achieved by a unique in-house thermal conductivity mapping setup and relating the data to local SEM EBSD maps. This provides the first conclusive proof that larger grain sizes can achieve higher thermal conductivity for this processing method and material system. This study also shows that control of the solidification can result in higher thermal conductivity. It was also the first to find that the build substrate (with or without support) has a large effect on thermal conductivity.

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Article
Publication date: 2 January 2018

Zhonghua Li, Ibrahim Kucukkoc, David Z. Zhang and Fei Liu

Surface roughness is an important evaluation index for industrial components, and it strongly depends on the processing parameters for selective laser molten Ti6Al4V parts. This…

3226

Abstract

Purpose

Surface roughness is an important evaluation index for industrial components, and it strongly depends on the processing parameters for selective laser molten Ti6Al4V parts. This paper aims to obtain an optimum selective laser melting (SLM) parameter set to improve the surface roughness of Ti6Al4V samples.

Design/methodology/approach

A response surface methodology (RSM)-based approach is proposed to improve the surface quality of selective laser molten Ti6Al4V parts and understand the relationship between the SLM process parameters and the surface roughness. The main SLM parameters (i.e. laser power, scan speed and hatch spacing) are optimized, and Ti6Al4V parts are manufactured by the SLM technology with no post processes.

Findings

Optimum process parameters were obtained using the RSM method to minimise the roughness of the top and vertical side surfaces. Obtained parameter sets were evaluated based on their productivity and surface quality performance. The validation tests have been performed, and the results verified the effectivity of the proposed technique. It was also shown that the top and vertical sides must be handled together to obtain better top surface quality.

Practical implications

The obtained optimum SLM parameter set can be used in the manufacturing of Ti6Al4V components with high surface roughness requirement.

Originality/value

RSM is used to analyse and determine the optimal combination of SLM parameters with the aim of improving the surface roughness quality of Ti6Al4V components, for the first time in the literature. Also, this is the first study which aims to simultaneously optimise the surface quality of top and vertical sides of titanium alloys.

Details

Rapid Prototyping Journal, vol. 24 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

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