Materials P
erformance and Characterization: V
olume 9 , Issue 4 ISSN: 2379-1365 Stock #: MPC2004 www.astm.org
Contents:
Special Issue on Advances in Powder Engineering
Guest Editor: Leszek A. Dobrzański
iii Overview
401 Powder Characterization Techniques—P. Ramakrishnan
426 Measurement of Water Content in Metal Powders—Louis-Philippe Lefebvre,
Jiajie Dai, Yannig Thomas, Malgosia Daroszewska, and Yadienka Martinez-Rubi
442 Processing of Microscale Aluminum Foamed Particles—D. Key,
Walid M. Daoush, and K. Morsi
452 Solidification Structures in Low-Alloyed Powder Metallurgy Steels Obtained through Permanent Liquid Phase Sintering Using a Master Alloy Containing Boron—Simon Gélinas, Jean-Nicolas Rousseau, and Carl Blais
470 Microstructural Evolution during Sintering and Fracture Behavior of Iron-Copper-Carbon Compacts Made with Elemental Powders—
Thomas F. Murphy and Bruce A. Lindsley
486 Microstructure and Properties of Nickel/Detonated Nanodiamond Composites Fabricated by Powder Metallurgy—Eman Toulba,
Mahmudun N. Chowdhury, Ahmed I. Ali, Ibrahim S. Qassem, and Walid M. Daoush
498 Hot Extrusion of a Commercial Aluminum Powder Metallurgy Metal Matrix Composite Material—M. F. Wilson, G. A. W. Sweet, M. Y. Amegadzie,
B. W. Williams, L. J. B. Smith, A. Taylor, R. L. Hexemer, I. W. Donaldson, and D. P. Bishop
514 Threshold Concentration of Surfactant Agent in Feedstocks Used for Low-Pressure Powder Injection Molding—Ghalya Ali, Vincent Demers,
Raphaël Côté, and Nicole R. Demarquette
528 Advances in Powder-based Technologies for Production of
High-Performance Sputtering Targets—F. M. Mwema, E. T. Akinlabi, O. P. Oladijo,
and A. D. Baruwa
543 Microstructure, Hardness, Wear, and Magnetic Properties of (Tantalum, Niobium) Carbide-Nickel–Sintered Composites Fabricated from Blended and Coated Particles—Hossam M. Yehia, Walid M. Daoush, F. Abdel Mouez,
Mohamed H. El-Sayed, and Ahmed E. El-Nikhaily
556 Comparison of the Structure and Properties of the Solid Co-Cr-W-Mo-Si Alloys Used for Dental Restorations CNC Machined or Selective Laser-Sintered—Lech B. Dobrzański, Anna Achtelik-Franczak, Joanna Dobrzańska,
and Leszek A. Dobrzański
Published by ASTM International | 100 Barr Harbor Drive | PO Box C700 | W. Conshohocken, PA 19428-2959
Materials Performance
and Characterization
Materials P
erformance and Characterization: V
olume 9 , Issue 4 ISSN: 2379-1365 Stock #: MPC2004 www.astm.org
Contents:
Special Issue on Advances in Powder Engineering
Guest Editor: Leszek A. Dobrzański
iii Overview
401 Powder Characterization Techniques—P. Ramakrishnan
426 Measurement of Water Content in Metal Powders— Louis-Philippe Lefebvre,
Jiajie Dai, Yannig Thomas, Malgosia Daroszewska, and Yadienka Martinez-Rubi
442 Processing of Microscale Aluminum Foamed Particles—D. Key,
Walid M. Daoush, and K. Morsi
452 Solidification Structures in Low-Alloyed Powder Metallurgy Steels Obtained through Permanent Liquid Phase Sintering Using a Master Alloy Containing Boron—Simon Gélinas, Jean-Nicolas Rousseau, and Carl Blais
470 Microstructural Evolution during Sintering and Fracture Behavior of Iron-Copper-Carbon Compacts Made with Elemental Powders—
Thomas F. Murphy and Bruce A. Lindsley
486 Microstructure and Properties of Nickel/Detonated Nanodiamond Composites Fabricated by Powder Metallurgy—Eman Toulba,
Mahmudun N. Chowdhury, Ahmed I. Ali, and Ibrahim S. Qassem
498 Hot Extrusion of a Commercial Aluminum Powder Metallurgy Metal Matrix Composite Material—M. F. Wilson, G. A. W. Sweet, M. Y. Amegadzie,
B. W. Williams, L. J. B. Smith, A. Taylor, R. L. Hexemer, I. W. Donaldson, and D. P. Bishop
514 Threshold Concentration of Surfactant Agent in Feedstocks Used for Low-Pressure Powder Injection Molding—Ghalya Ali, Vincent Demers,
Raphaël Côté, and Nicole R. Demarquette
528 Advances in Powder-based Technologies for Production of
High-Performance Sputtering Targets—F. M. Mwema, E. T. Akinlabi, O. P. Oladijo,
and A. D. Baruwa
543 Microstructure, Hardness, Wear, and Magnetic Properties of (Tantalum, Niobium) Carbide-Nickel–Sintered Composites Fabricated from Blended and Coated Particles—Hossam. M. Yehia, Walid M. Daoush, F. Abdel Mouez,
Mohamed H. El-Sayed, and Ahmed E. El-Nikhaily
556 Comparison of the Structure and Properties of the Solid Co-Cr-W-Mo-Si Alloys Used for Dental Restorations CNC Machined or Selective Laser-Sintered—Lech B. Dobrzański, Anna Achtelik-Franczak, Joanna Dobrzańska,
and Leszek A. Dobrzański
Published by ASTM International | 100 Barr Harbor Drive | PO Box C700 | W. Conshohocken, PA 19428-2959
Materials Performance
and Characterization
www.astm.org Printed in the USA.
CO-EDITORS Dr. Richard W. Neu
Georgia Institute of Technology Atlanta, GA, USA
Dr. George E. Totten
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EDITORIal bOaRD
Dr. lutz-Michael berger
Fraunhofer Institute for Ceramic Technologies and Systems Dresden, Germany
Rodney boyer
RBTi Consulting Issaquah, WA, USA
Prof. lauralice Canale
EESC-Universidade de São Paulo São Carlos, SP, Brazil
Mr. brian Cochran
Wabash, IN, USA
Prof. leszek a. Dobrzański
ASKLEPIOS Ltd. Gliwice, Poland
Dr. ana Sofia C. M. D’Oliveira
Universidade Federal do Paraná Curitiba, PR, Brazil
Dr. Richard j. Fields
Grayson, GA, USA
Mr. Robert j. Glodowski
East Metals North America LLC Pittsburgh, PA, USA
Dr. jianfeng Gu
Shanghai Jiao Tong University Shanghai, China
Dr. Nikhil Gupta
New York University Brooklyn, NY, USA
Dr. Mohamed Hamed
McMaster University Hamilton, ON, Canada
Dr. volker Heuer
ALD Vacuum Technologies GmbH Hanau, Germany
Dr. W. Steven johnson
Georgia Institute of Technology Atlanta, GA, USA
Dr. Toshiharu Kazama
Muroran Institute of Technology Hokkaido, Japan
Dr. Fred Klaessig
Pennsylvania Bio Nano Systems Doylestown, PA, USA
Dr. Nikolai Kobasko
Technologies Inc. Akron, OH, USA
Dr. antti S. Korhonen
Aalto University of Science and Technology
Aalto, Finland
Dr. Hong liang
Texas A&M University College Station, TX, USA
Dr. Stephen liu
Colorado School of Mines Golden, CO, USA
Dr. Roberto lopez-anido
University of Maine Orono, ME, USA
Dr. Reto luginbüehl RMS Foundation Bettlach, Switzerland Dr. jianbin luo Tsinghua University Beijing, China
Prof. Xinmin luo
Jiangsu University Zhenjiang, Jiangsu, China
Dr. lemmy Meekisho
Portland State University Portland, OR, USA
Dr. Rafael David Mercado-Solis
Universidad Autonoma de Nuevo Leon
Nuevo Leon, Mexico
Ms. Marybeth Miceli
Miceli Infrastructure Consulting, LLC Los Angeles, CA, USA
Dr. jin K. Montclare
New York University New York, NY, USA
Dr. S. v. S. Narayana Murty
Vikram Sarabhai Space Center Trivandrum, India
Dr. Rosa Simencio Otero
Universidade de São Paulo São Carlos, Brazil
Dr. bojan Podgornik
Institute of Metals and Technology Ljubljana, Slovenia
Dr. K. Narayan Prabhu
National Institute of Technology Karnataka State, India
barbara Rivolta Politecnico di Milano Milano, Italy Dr. jeremy Robinson University of Limerick Limerick, Ireland Dr. Satyam Sahay
John Deere Technology Center India
Magarpatta City, Pune, India
Prof. Dr.-Ing. hab. berthold Scholtes
University of Kassel Kassel, Germany
Dr. Nima Shamsaei
Auburn University Auburn, AL, USA
Dr. Preet Singh
Georgia Institute of Technology Atlanta, GA, USA
Dr. Richard D. Sisson, jr.
Worcester Polytechnic Institute Worcester, MA, USA
Prof. Igor Sizov
East Siberia State University of Technology and Management Ulan-Ude, Russia
Dr. Sabu Thomas
Mahatma Gandhi University Kottayam, India
Ms. Eva Troell
RISE Research Institutes of Sweden, Mölndal, Sweden
Dr. Simon C. Tung
Tung Innovation Technology Consulting Inc.
Rochester Hills, MI, USA
Dr. Mathias Woydt
BAM Federal Institute for Materials Research and Testing Berlin, Germany
Mr. jingguo (jing Guo) Zhang
Shanghai HuiZhi Advanced Materials & Technology Co., Ltd. Shanghai, China
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Materials Performance and Characterization (Print ISSN
Overview
Powder Engineering: Where Have You Been?
Where Are You Going?
The title of this overview is associated with the chorus of a song written and sung since 1997 by British musician, singer and racing driver Christopher Anton“Chris” Rea. It reflects on progress generally, which includes this crucial area of powder engineering as a modern group of technologies.
The Industrial Revolution began in the late 18th century, and it was associated with the invention of the steam engine and the development of factory production. Its subsequent stages led to the current stage known as Industry 4.0, characterizing the full digital revolution that is taking place dynamically. Progress is largely determined by cyber-physical systems, including large data sets and analyses, autonomous robots, simulations, horizontal and vertical system integration, industrial Internet of Things, cybersecurity, cloud computing, and augmented reality. They provide communication between machines and intelligent products and create a virtual copy of the physical world through digital twins. The model that was developed, however, does not meet all expectations and require-ments and cannot be considered as a full holistic model of technological development at the Industry 4.0 stage. It was not noticed that apart from the cyber-IT module, the development of materials, technological processes, and technological machines guaranteeing them should be taken into account. Although additive technologies have been included in this model, it is highly insufficient. Other technologies are present and they are necessary for the normal function of the industry. Their development is expected too. For this reason, the Industry 4.0 model requires supplementation and augmentation.
Industry 4.0 augmented a holistic model that was introduced by the author in the form of an octahedron, and in its technology platform, it includes four components requiring systematic development, among other multi-faceted and various technological processes, including additive. None of these four components could be omitted. New technologies cause integrated sustainable industrial development (ISID) by introducing new goods to the market and improving production efficiency. The evolutionary introduction of advanced digitized production (ADP) in the fourth stage of the Industry 4.0 industrial revolution involves the combination of hardware, software, and con-nectivity. The dissemination of advanced digital production technologies (ADP) consists of the development and use of artificial intelligence, analysis of large data sets, cloud computing, Internet of Things (IoT), and advanced robotics, and it successively combines physical and digital production systems. According to the UNIDO Report published at the end of 2019, regarding the current year 2020, only ten countries in the world have the ability to introduce ADP technologies, owning together 90% of patents in this area and exporting as much as 70% of world turnover covering this range. It was estimated that the next 40 countries have a chance to join this elite set, although to a small extent. It is only an estimate of the opportunities. Of course, it is the task of each of these countries to fit in that vacant 10%. A country that will not be able to do so will fall out of the world’s lead, and in the next few decades it will become only a basin of cheap labor and raw materials, if it has any. It requires enormous national intellectual and investment effort in each of these aspiring countries. Facts and practical industrial and economic activities will be important.
For obvious reasons, it is in the general interest that the distance between these top countries and the rest is not deepened. On the contrary, it is in the general interest that this leading group of countries be as numerous as possible and that these world advanced digitized production ADP technologies be shared by the widest group of entities in the world.
Modern technologies, with almost no exception, are advanced and require significant IT support. They undoubtedly form part of the cyber-physical systems. Severe scientific and engineering analyses of any modern technologies require broad consideration of the given context. This special issue is dedi-cated to this select group of technologies, which in a general sense could be understood as additive tech-nologies. This special issue addresses powders of metal and their alloys and ceramics, as well as technology for the production of products using them. It is the technological scope that plays a funda-mental role in the current stage of Industry 4.0 development of the industrial revolution. The widespread variety of technologies using powders of metals, their alloys, and numerous ceramic materials requires a departure from the traditional understanding of this engineering area as powder metallurgy, which has only partially become adequate as a result of development. These powders are wholly or partly used in a more diverse area, covering almost 50 detailed technologies, informing the dynamic growth of com-pound annual growth rates in many global markets. It requires the introduction of a more general con-cept, which is fully adequate to the range of currently known and applied technologies using powders of metals as well as their alloys and ceramics. There is an attempt to define the entire subject matter as powder engineering. It is a set of all technical activities that are used to produce powders of the metals, their alloys and ceramics, and to use powders thus produced for the production of solid, porous, and skeletal materials and products, and possibly infiltrated with other low-melted alloys, as well as applying various coatings and surface layers using these powders. It is a pervasive range of modern and very advanced technology. While preparing the concept of this special issue, almost exclusively these aspects were taken into account. Various aspects of these problems are included in individual papers presented in this special issue. It seems that powder engineering is now the more appropriate name for this complex technical area, hence the title of this special issue.
However, one cannot resist some philosophical reflections when writing the editorial. It is impossible today not to pay attention to a completely different aspect, which is associated with the message of the motto of this introduction. We are talking about the dynamic development of the industry, convinced that humankind is the sole author of this emerging success. Meanwhile, the considerable slump in this progress depends on a completely different reason. A small nanometric natural object of substantially spherical shape, though somewhat pleomorphic, with a diameter of 60–140 nm, surrounded by bright spikes of 9–12 nm in length, giving the impression of resemblance to the corona, has wreaked havoc on economic systems. It is the SARS-CoV-2 virion of the enveloped virus, whose genome is a positive-polarized single-stranded ribonucleic acid RNA giving severe acute respiratory syndrome and other severe diseases in the human body defined as Coronavirus Disease 2019 COVID-19. The pandemic scale covered the entire World in less than ten weeks. Billions of people around the world need to follow the most crucial slogan today“Stay at home.” And this is no longer about development, but about physical survival. But at the same time, we have to understand that it was man and his inventiveness and great achievements that contributed to the spread of this virus. The plane which is one of our greatest technical achievements and the developed air transport and independence in international tourism has signifi-cantly contributed to the scale of this impact which is still impossible to define with certainty. The nanometric object challenged the world, whose diameter is 100 trillion times greater than its size. It is impossible to resist the association that it is also a kind of specific powder that so significantly determines the development of the modern world. It is an entirely unexpected impact of nanotechnology scale on global life in the World, and not the achievements of those we use to pride ourselves on, such as
Richard P. Feymann, K. Eric Drexler, Harold Kroto, Robert Curl, Richard Smalley, Andre Geim, Konstantin S. Novoselov, Jack Kilby, Hiroshi Amano, Isamu Akasaki, Shūji Nakamura, mainly Nobel Prize winners. It is impossible to resist the impression that this is a powerful signal from nature teaching elemental humility. It is worth recalling the words of the great Polish romantic poet, Adam Mickiewicz,“In one case, the council does not hamper, When Humility takes advises from Wisdom.” Of course, we remain in the legitimate hope that we will soon return to the path of integrated sustainable industrial development (ISID). However, without a doubt, the situation will never be the same again as before.
The special issue is opened by the paper entitled“Powder Characterization Techniques,” in which Ramakrishnan points out that a reasonable selection of relevant and appropriate powder characterization techniques will ensure predictable powder behavior during the manufacturing process resulting in con-sistent and reliable products. The author characterizes methods and assessment techniques of structure, chemistry, morphology, size, shape, their distribution, different densities, flow, porosity, compressibility, friction, shear, residual stress and to obtain a defect-free product. Introduction to the production of finer powders requires the use of X-ray photoelectron spectroscopy, scanning electron microscopy, Laser light diffraction, X-ray computed tomography scan, and Atomic Force Microscopy. Differential thermal analysis has been used with an emphasis on powder cleanliness and internal particle porosity. The dynamic powder testing using powder Rheometer to measure dynamic flowability from the measure-ment of axial and rotational forces acting on the rotating blade and the study of spreadability and flow-ability of powders by rotating drum instruments are important due to the requirements of modern additive technologies.
A team of five authors from Canada, led by Louis-Philippe Lefebvre, took a more detailed approach to selected methodological issues in the paper on“Measurement of water content in metal powders.” It is recognized that humidity affects some properties of metallic powders. This paper evaluates the water content in titanium powders using different techniques (gravimetry, Karl Fisher titration, quantification of volatiles with a relative humidity sensor). The results showed that the adsorption of water is a function of the relative humidity in the environment and the characteristics of the powders. While some vari-ability has been observed, the measurement of volatiles with the relative humidity sensor allowed dis-criminating powders with water contents ranging from 0 to 108 ppm. The amount of water measured using the gravimetric technique was not sensitive enough to monitor precisely the small amount of water adsorb/desorb on the powders investigated. Additional studies are needed because there is still present no standard method validated or specially adapted for the evaluation of the water content in metallic powders.
The next paper titled“Processing of Microscale Aluminum Foamed Particles” was developed by Key, Daoush, and Morsi from the USA, Egypt, and Saudi Arabia, respectively. Microscale particles of alu-minum (Al)-titanium dihydride (TiH2) foaming precursors were used and their foaming characteristics were examined. The external and internal features and dimensions of these precursor particles were found to be highly dependent on the mechanical milling process and the use of a process control agent (methanol) during milling. Foaming in argon was found to yield better foaming characteristics than that in air.
Toulba and his six-member team from Egypt and Saudi Arabia have prepared a paper on “Micro-structure and Properties of Nickel/Detonated Nanodiamond Composites Fabricated by Powder Metallurgy.” The homogenous diamond powder/Ni composite mixtures were cold-pressed in a cylin-drical die shape under compaction pressure of 400 MPa followed by sintering at 1000°C for 120 min under a controlled atmosphere of 1:3 hydrogen/nitrogen gas mixture. As the detonated nanodiamond content was increased in the nickel matrix the density of the sintered samples was decreased. The coefficient of thermal expansion and electrical conductivity was decreased but the hardness was
increased by increasing the detonated nanodiamond weight per cent. The results of the microstructure show a good distribution of the detonated nanodiamond in the nickel matrix specially 0.8wt% diamond/ Ni sintered sample.
The next paper also deals with structural issues. Gélinas, Rousseau, and Blais from Canada have pub-lished the paper,“Solidification Structures in Low-Alloyed Powder Metallurgy Steels Obtained through Permanent Liquid Phase Sintering Using a Master Alloy Containing Boron.” Sintering of tested steels takes place through permanent liquid phase sintering (LPS). The main objective of this paper is to de-scribe the relationship that exists between the concentration of pre-alloyed molybdenum and the crystal structure of the boride/borocarbide eutectic component upon cooling at the end of the sintering cycle. Characterization in optical and scanning electron microscopy (SEM) combined with electron-backscat-tered diffraction (EBSD) and energy-dispersive X-ray spectrometry (EDS) revealed that increasing the pre-alloyed molybdenum content not only increased the volume fraction of liquid phase but also modi-fied the morphology and the nature of the boron-rich eutectic. Changing the pre-alloyed molybdenum content from 0.5 wt.% to 0.85 wt.% transformed the discontinuous M2B boride to a continuous M23 (C, B) 6 borocarbide phase, causing a drastic decrease in strength despite the higher densification ob-served at 0.85 wt. % molybdenum. The effect of molybdenum on the LPS process of boron PM steels is undeniable and was found out to occur after the initial formation of the liquid phase. Differential scan-ning calorimetry (DSC) revealed no difference in the endothermic melting peaks temperature for both the concentration of molybdenum.
“Microstructural Evolution During Sintering and Fracture Behavior of Iron-Copper-Carbon Compacts Made with Elemental Powders” is the title of the paper prepared by Murphy and Lindsley from the USA. The effect of sintering on the development of the microstructure is investigated, where the copper particles melt and flow into the interconnected pore structure, relocate within the iron-base matrix, and create more interfacial area for diffusion. With this combination of enlarged copper-iron contact area and the presence of the liquid phase, diffusion is improved and enhancements in both physical and mechanical properties are realized. Alloying strengthens not only the surfaces of the particles but also the locations where neighboring particles are into contact during compaction. These sintered particle-to-particle contacts are frequently small in cross-sectional area. Fractography is used to show the change in fracture behavior as copper diffusion is affected by sintering times and temperatures.
Another paper, “Hot Extrusion of a Commercial Aluminum Powder Metallurgy Metal Matrix Composite Material,” was prepared by Wilson and colleagues from two centers in Canada. Sintered preforms made of an aluminum powder metallurgy 2000 series metal matrix composite designed for press-and-sinter applications were forward extruded at 450°C under displacement rates of 254 and 2032 mm/min. Solid round bars 10 and 15 mm and C-channel and round tubing profiles were produced by extrusion under these conditions. Significant gains in tensile yield strength (10%), UTS (20%), and tensile ductility (400%) when compared to the non-extruded T6 counterpart occurred. Such enhance-ments were attributed to the attenuation of full theoretical density, disruption of the residual oxide net-work, and the development of a partial duplex fiber texture with strong〈111〉 and moderate 〈100〉 fiber components within the extruded PM products.
Next, a group of four authors from Canada prepared a paper entitled“Threshold Concentration of Surfactant Agent in Feedstocks Used for Low-Pressure Powder Injection Molding.” As little as 0.20 vol.% of stearic acid or oleic acid in paraffin wax-based feedstock is enough to produce the surfactant effect, leading to a significant increase in the moldability of feedstocks (e.g., fourfold longer injected length). This threshold concentration of surfactant agent in paraffin wax-based feedstocks was established with different powder grades, shapes and sizes. For feedstocks containing paraffin wax and surfactant agents,
the presence of a discontinuity in the viscosity profiles was reproduced using three different measure-ment approaches. The influence of surfactant agents on viscosity depends on the main binder constituent used in the feedstock formulation. The moldability of paraffin wax-based feedstocks was significantly affected by the proportion of the surfactant agents, while that of beeswax-based feedstocks was not affected by the presence of stearic acid or oleic acid.
Four authors from South Africa, Kenya, and Botswana wrote a paper on“Advances in Powder-based Technologies for Production of High-Performance Sputtering Targets.” The authors emphasize that the paper is serving in the optimization and development of advanced targets for Industry 4.0. With the increasing demand for high-performance thin films and coatings, such as high entropy alloy films, the quality of the targets used for sputtering is very crucial for application in various fields including medical, electronics and energy. In the paper, progress on the powder metallurgy (PM) on the manu-facturing of sputtering targets is detailed. Advances in various powder technologies, process parameters and conditions, and their interrelationships with properties and performance of targets and sputtered thin films are discussed, synthesized and general and specific trends derived.
Yehia and colleagues from Egypt and Saudi Arabia prepared the paper“Microstructure, Hardness, Wear and Magnetic Properties of (T, Nb)C/Ni Sintered Composites Fabricated from Blended and Coated Particles.” Different nickel content was added to (Tantalum, niobium) carbide powders by two different methods namely, blending and electroless coating. The (Tantalum, niobium) carbide-nickel sintered materials which prepared by the electroless nickel coating of (Tantalum, niobium) carbide particles have a homogeneous microstructure and exhibit higher relative density, hardness and low specific wear rate than the samples of the (Tantalum, niobium) carbide-nickel sintered materials prepared by blending of nickel with the (Tantalum, niobium) carbide powders. The saturation magnetization is increased by increasing the nickel content. The results of the microstructure show a good distribution of the (Tantalum, niobium) carbide particles in the nickel matrix.
The last, but not least, paper is prepared by our four-person team headed by Lech Dobrzański from Poland, entitled“Comparison of the Structure and Properties of the Solid Co-Cr-W-Mo-Si Alloys Used for Dental Restorations CNC Machined or Selective Laser-Sintered.” This paper fastens with peculiar buckle all the papers collected in this special issue. This Overview is very general and characterizes all technologies related to the production of metal and ceramic powders and the production of products from these powders. One of the technologies discussed in it is additive methods, including selective laser sintering SLS. This article deals with the current topic of our research on materials and technologies in the application for the production of prosthetic restorations. The subject of research of this paper is a cobalt alloy with chromium and with other elements as a modification of Vitalium alloys type. It is the alloy commonly used in dentistry for different restorations. The purpose of the paper is comparing the impact of SLS selective laser sintering technology and CNC machining methods on the structure and properties of solid Co-Cr-W-Mo-Si alloys. The use of SLS additive technology for the production of prosthetic components made of Co-Cr alloys is the best choice among the methods currently used in dentistry. The use of SLS technology together with the digitization of design and manufacturing proc-esses is an important element in implementing the Dentistry 4.0 approach as part of the Industry 4.0 stage of the industrial revolution. Although this paper deals with specific issues, it confirms the latest development trends of modern industry, about which I wrote at the beginning of this Overview.
The team of authors, as well as the guest editors of this special issue on Advances in Powder Engineering, offer it to PT readers today. This name is new, despite the fact that the first reports of the use of powders in the manufacture of products were recorded 3000 years BC in ancient Egypt, and the ancient Incas made a precious stone from gold and other precious metals by this method. Mass production dates from the late nineteenth century.
As guest editor of this special issue, I put a lot of time and energy into its preparation. I will be extremely satisfied if the articles collected in it prove to be interesting, directly useful for carrying out everyday practical tasks, and also inspiring in undertaking new scientific and research challenges.
Have a nice and engaging read.
Professor Leszek A. Dobrzański Medical and Dental Engineering Center for Research, Design and Production ASKLEPIOS Gliwice, Poland
