scholarly journals The Detection of Unfused Powder in EBM and SLM Additive Manufactured Components

2020 ◽  
Vol 14 (6) ◽  
pp. 1025-1035
Author(s):  
Ahmed Tawfik ◽  
Mohamed Radwan ◽  
Mazen Ahmed Attia ◽  
Paul Bills ◽  
Radu Racasan ◽  
...  
Keyword(s):  
Density Measurement ◽  
Spherical Shape ◽  
Powder Size ◽  
Voxel Size ◽  
Volume Graphics ◽  
Core Technology ◽  
Powder Particles ◽  
X Ray Computed ◽  
Quality Assurance Standards ◽  
Subtractive Machining

Additive manufacturing (AM) is recognized as a core technology for producing high value, complex, and individually designed components as well as prototypes, giving AM a significant advantage over subtractive machining. Selective laser melting (SLM) or electron beam melting (EBM) are two of the main technologies used for producing metal components. The powder size varies, depending on the technology and manufacturer, from 20–50 μm for SLM and 45–100 μm for EBM. One of the current barriers for implementing AM for most industries is the lack of build repeatability and a deficit in quality assurance standards. The mechanical properties of the components depend critically on the density achieved; therefore, defect analysis and detection of unfused powder must be carried out to verify the integrity of the components. Detecting unfused powder in AM parts using X-ray computed tomography (XCT) is challenging because detection relies on variations in density. Unfused particles have the same density as the manufactured parts; therefore, detection is difficult using standard methods for density measurement. This study presents a methodology to detect unfused powders in SLM and EBM-manufactured components. Aluminum and titanium artefacts with designed internal defects filled with unfused powder are scanned with XCT and the results are analyzed with VGSTUDIO Max 3.0 (Volume Graphics, Germany) software package. Preliminary results indicate that detecting unfused powder in an aluminum SLM artifact with a 9.5 μm voxel size is achievable. This is possible because of the size of the voids between the powder particles and the non-uniform shape of the particles. Conversely, detecting unfused powder in the EBM-manufactured titanium artifact is less challenging owing to the uniform spherical shape and slightly larger size of the particles.

scholarly journals Development of an Additive Manufactured Artifact to Characterize Unfused Powder Using Computed Tomography

2020 ◽  
Vol 14 (3) ◽  
pp. 439-446 ◽  
Author(s):  
Ahmed Tawfik ◽  
◽  
Paul Bills ◽  
Liam Blunt ◽  
Radu Racasan
Keyword(s):  
Computed Tomography ◽  
Data Analysis ◽  
Additive Manufacturing ◽  
Voxel Size ◽  
Core Technology ◽  
Scan Time ◽  
Time Required ◽  
Porosity Analysis ◽  
The Impact ◽  
Subtractive Machining

Additive manufacturing (AM) is recognized as a core technology for producing high-value components. The production of complex and individually modified components, as well as prototypes, gives additive manufacturing a substantial advantage over conventional subtractive machining. For most industries, some of the current barriers to implementing AM include the lack of build repeatability and a deficit of quality assurance standards. The mechanical properties of the components depend critically on the density achieved. Therefore, defect/porosity analysis must be carried out to verify the components’ integrity and viability. In parts produced using AM, the detection of unfused powder using computed tomography is challenging because the detection relies on differences in density. This study presents an optimized methodology for differentiating between unfused powder and voids in additive manufactured components, using computed tomography. Detecting the unfused powder requires detecting the cavities between particles. Previous studies have found that the detection of unfused powder requires a voxel size that is as small as 4 μm3. For most applications, scanning using a small voxel size is not reasonable because of the part size, long scan time, and data analysis. In this study, different voxel sizes are used to compare the time required for scanning, and the data analysis showing the impact of voxel size on the detection of micro defects. The powder used was Ti6Al4V, which has a grain size of 45–100 μm, and is typically employed by Arcam electron beam melting (EBM) machines. The artifact consisted of a 6 mm round bar with designed internal features ranging from 50 μm to 1400 μm and containing a mixture of voids and unfused powder. The diameter and depth of the defects were characterized using a focus variation microscope, after which they were scanned using a Nikon XTH225 industrial CT to measure the artifacts and characterize the internal features for defects/pores. To reduce the number of the process variables, the measurement parameters, such as filament current, acceleration voltage, and X-ray filtering material and thickness were kept constant. The VGStudio MAX 3.0 (Volume Graphics, Germany) software package was used for data processing, surface determination, and defects/porosity analysis. The main focus of this study is to explore the optimal methods for enhancing the detection of pores/defects while minimizing the time taken for scanning, data analysis, and determining the effects of noise on the analysis.

The Effect of Annealing to the Hardness of Oxide Dispersion Strengthened (ODS) Fe-15Cr-0.3Y2O3 Alloy

2017 ◽  
Vol 888 ◽  
pp. 428-431
Author(s):  
Farha Mizana Shamsudin ◽  
Yusof Abdullah ◽  
Shahidan Radiman ◽  
Nasri A. Hamid
Keyword(s):  
Vickers Hardness ◽  
Spherical Shape ◽  
Hardness Test ◽  
Oxide Dispersion Strengthened ◽  
Oxide Dispersion ◽  
Alloy Matrix ◽  
Hardness Tester ◽  
Powder Particles ◽  
Average Size ◽  
Vickers Hardness Test

The objective of this study is to investigate the microstructure and effect of annealing to the hardness properties of oxide dispersion strengthened (ODS) Fe-15Cr-0.3Y2O3 alloy. This type of alloy was prepared by mechanical alloying (MA) method followed by compacting and sintering. The microstructure of milled Fe-15Cr-0.3Y2O3 alloy powders and pellet was examined by using field emission scanning electron microscope (FESEM). The milled alloy powders consist of nearly spherical shape of powder particles with average size of 10 µm. For the alloy pellet microstructure, the formations of Y2O3 nanoparticles with average size of 5 nm were observed indicating the dispersion and incorporation of this nano-scale dispersoids into the alloy matrix. Fe-15Cr-0.3Y2O3 alloy pellet was annealed at temperature of 600°C, 800°C and 1000°C, respectively for the Vickers hardness test. The Vickers hardness test was performed by using a micro-Vickers hardness tester with a load of 200 gf. The hardness value (HV) of this alloy pellet started to decrease at temperature of 600°C indicating the grain growth of this material at high temperature

scholarly journals Influence of Glass Powder Size Sorting on Properties of Composite Systems

2016 ◽  
Vol 47 (1) ◽  
pp. 25-31
Author(s):  
K. Dědičová ◽  
P. Valášek
Keyword(s):  
Glass Powder ◽  
Adhesive Bonding ◽  
Raw Materials ◽  
Average Particle Size ◽  
Polymeric Materials ◽  
Average Particle ◽  
Powder Size ◽  
Size Sorting ◽  
Powder Particles ◽  
Size Of Particles

Abstract Glass powder ranks among the secondary raw materials, which can be used in the interaction with polymeric materials. In the present experiment the polymeric/epoxy particle composite with different sizes of glass powder particles is described. Such utilization of recyclable materials is environmental-friendly and should be preferred. The size of particles forming the filler of the described composites is one of the key characteristics affecting the mechanical properties. Due to the properties of the systems filled with glass powder, these materials can potentially be used in agriculture (renovations, adhesive bonding, cementing, etc.). In the experiment, glass powder was dimensionally sorted through sieves. Three fractions of glass powder with particles size of 0−30, 30−50, and 50−90 μm were created and utilized, the average particle size being 18.7, 38.7, and 72.6 μm, respectively. The interaction of the 18.7 μm particles did not lead to a statistically significant decrease of shear strength values in the interval 0−20 vol.%. The presence of glass powder, however, in all cases decreased tensile strength.

Study of mechanical spheroidization of powders obtained from waste metal shavings

2021 ◽  
pp. 41-46
Author(s):  
A. D. Samukov ◽  
M. V. Cherkasova ◽  
M. P. Kuksov ◽  
S. V. Dmitriev
Keyword(s):  
Energy Consumption ◽  
3D Printing ◽  
Spherical Shape ◽  
Spherical Particles ◽  
High Tech ◽  
Metal Powders ◽  
Powder Preparation ◽  
Russian Science ◽  
Additional Energy ◽  
Powder Particles

This paper covers the search for a new method for generating metal powders for additive manufacturing. Raw materials for 3D printing are subject to certain requirements regarding the spherical shape of the powder particles, which are not easily met. The powder preparation methods used in the powder metallurgy may not be directly used for 3D printing without additional energy consumption for the spheroidization operation. More high-tech principles of melt dispersion shall be used for the spheroidization (atomization) of powder particles. Metal waste grinding in ball or vibrating mills generally yields plate-like particles, also requiring the use of energy-intensive atomization technologies. However, an analysis of related foreign research provided an alternative that is to use two-stage grinding to obtain spherical metal powder particles. Continued research in mechanical spheroidization enables the simultaneous manufacture and grinding of the required spherical particles while maintaining practically the same energy consumption that had been previously required for the grinding process. In order to form a research program and establish the optimal grinding size in terms of energy consumption and the dependence between the ball diameter and the grinding and spheroidization results for metal particles, respective preliminary experiments were carried out. The results of these experiments were then used to formulate the conclusions required to develop a method for establishing the optimal grinding ball charge level and composition. The study was carried out under the grant issued by the Russian Science Foundation (project No. 20-79-10125).

scholarly journals Characteristics of the Mg-Zn-Ca-Gd Alloy after Mechanical Alloying

Materials ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 226
Author(s):  
Sabina Lesz ◽  
Bartłomiej Hrapkowicz ◽  
Małgorzata Karolus ◽  
Klaudiusz Gołombek
Keyword(s):  
Mechanical Alloying ◽  
Milling Time ◽  
Hardness Test ◽  
Medical Application ◽  
Biological Properties ◽  
Powder Size ◽  
Powder Morphology ◽  
Average Value ◽  
Powder Particles ◽  
Average Size

Magnesium-based materials are interesting alternatives for medical implants, as they have promising mechanical and biological properties. Thanks to them, it is possible to create biodegradable materials for medical application, which would reduce both costs and time of treatment. Magnesium as the sole material, however, it is not enough to support this function. It is important to determine proper alloying elements and methods. A viable method for creating such alloys is mechanical alloying, which can be used to design the structure and properties for proper roles. Mechanical alloying is highly influenced by the milling time of the alloy, as the time of the process affects many properties of the milled powders. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS) were carried out to study the powder morphology and chemical composition of Mg65Zn30Ca4Gd1 powders. Moreover, the powder size was assessed by granulometric method and the Vickers hardness test was used for microhardness testing. The samples were milled for 6 min, 13, 20, 30, 40, and 70 h. The hardness correlated with the particle size of the samples. After 30 h of milling time, the average value of hardness was equal to 168 HV and it was lower after 13 (333 HV), 20 (273 HV), 40 (329 HV), and 70 (314 HV) h. The powder particles average size increased after 13 (31 μm) h of milling time, up to 30 (45–49 μm) hours, and then sharply decreased after 40 (28 μm) and 70 (12 μm) h.

Effect of X-Ray Computed Tomography Scanning Parameters on the Estimated Porosity of Foam Specimens

2011 ◽  
Vol 110-116 ◽  
pp. 808-815 ◽  
Author(s):  
Jagadeesha Kumar ◽  
Abdul Hadi G. Abulrub ◽  
Alex Attridge ◽  
Mark A. Williams
Keyword(s):  
Computed Tomography ◽  
Focal Spot ◽  
Ct Scanning ◽  
Spot Size ◽  
Voxel Size ◽  
X Ray ◽  
Computed Tomography Scanning ◽  
X Ray Computed ◽  
Tomography Scanning ◽  
Segmentation Threshold

X-Ray Computed Tomography (CT) scanning is an effective method for estimating the porosity of various engineering materials and biomedical specimens such as tissue scaffolds and bones. However, the scanning and analysis parameters play a significant role in the accuracy of the porosity value determined from CT scan. This paper presents details of an investigation carried out to understand the effect of system parameters, namely the voxel size, X-ray focal spot size and segmentation threshold, on the estimated porosity by taking an example of safety-critical foam used for impact protection applications. Different voxel resolutions and focal spot sizes are selected in a total of 12 scanning tests and the effect of segmentation threshold is analyzed on each of these tests. The study indicates that the obtained porosity value is greatly influenced by the choice of voxel size at larger spot sizes and less influenced at smaller spot sizes. The threshold also has significant effect on the porosity value, especially at larger voxel sizes.

scholarly journals The Microstructural Revolution of Ti-6Al-4V Specimens Fabricated by Selective Laser Sintering of Pre-alloyed Powders

2019 ◽  
Vol 57 (3A) ◽  
pp. 103 ◽  
Author(s):  
Thuyet Minh Nguyen ◽  
Viet Hoang Nguyen ◽  
Jin-Chun Kim
Keyword(s):  
Complex Geometry ◽  
Selective Laser Sintering ◽  
Spherical Shape ◽  
Laser Sintering ◽  
Metal Object ◽  
Α Phase ◽  
Grain Structures ◽  
Direct Fabrication ◽  
Powder Particles ◽  
Columnar Grain

Selective laser sintering (SLS) is known as a cutting-edge technique to manufacture complex geometry products. Among various kinds of materials, Ti-6Al-4V is one of the most popular materials for the SLS process. The as-built Ti-6Al-4V products were widely applied in many applications such as aerospace, automobile, and especially in medical and implant parts. The purpose of this research is to investigate the microstructure and other properties of Ti6Al4V pre-alloyed powders produced by selective laser sintering technique. Through this research, the direct fabrication of Ti6Al4V metal object by SLS machine has been carried out using MetalSys250 machine. Different parameters of the SLS process were used to produce 1cm x1cmx1cm cubic samples and then microstructure, as well as mechanical properties of the as-built samples were investigated. Powder particles are fully dense, possess a spherical shape and are composed of acicular α phase. The as-build sample shows the oriented acicular martensitic phase with the defined columnar grain structures.

scholarly journals Perspectives of the industrial recycling of hard-alloy materials waste by electro-erosive grinding

2018 ◽  
Vol 224 ◽  
pp. 01010
Author(s):  
Kharis Rakhimyanov ◽  
Valentina Marusina
Keyword(s):  
Mechanical Properties ◽  
Specific Surface ◽  
Tungsten Carbide ◽  
Hard Alloy ◽  
Physical And Mechanical Properties ◽  
Spherical Shape ◽  
Production Waste ◽  
Hard Alloys ◽  
Sustainable Technologies ◽  
Powder Particles

The creation of efficient industries is possible by using sustainable technologies based on the processes of recycling of the production waste. First of all, it refers to expensive material waste, including hard alloys. The electro-erosive grinding is considered to be the effective method of recycling such materials. The results of research on recycling the tungsten-cobalt hard alloy show the possibility of obtaining tungsten-carbide powders possessing improved physical and mechanical properties. The technology mentioned is also perspective for recycling tungstenless hard-alloy waste both at the laboratory devices equipped with the RC-generator and at the industrial installations of bulky grinding. It is established experimentally that the electro-erosive grinding of the TN20 tungstenless hard alloy at the laboratory provides obtaining the main volume (up to 85%) of the powder particles of the spherical shape having a dimension of 5 µm and the specific surface of 31.5 m2/g. Higher physical and mechanical properties of powders are also provided during recycling the TN20 alloy waste at the industrial installations of bulky grinding.

scholarly journals Analysis of Powder Binder Separation through Multiscale Computed Tomography

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 329
Author(s):  
Shidi Yang ◽  
Qiaoli Xu ◽  
Chengcheng Liu ◽  
Xin Lu ◽  
Xuanhui Qu ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Volume Fraction ◽  
Value Distribution ◽  
Green Body ◽  
Low Resolution ◽  
X Ray ◽  
Powder Particles ◽  
X Ray Computed ◽  
Powder Content ◽  
Submicron Resolution

In this study, X-ray computed tomography was used to analyze powder binder separation in TC4 green bodies. Firstly, for the scanned results of the whole green body, because of the relative low resolution (36 µm), the powder binder separation can only be analyzed by using gray value distribution. Then, local regions (areas near the gate and the central parts) were scanned by using a much higher resolution (2.3 µm). Both of the volume fraction of powder content and gray value distributions indicate that powder particles tend to accumulate in the central parts. Finally, based on the results tested by using submicron resolution (0.8 µm), the effects of the volume and morphology of the powder particles on the powder binder separation were analyzed.

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