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Recent Application of Powder Metallurgy Materials

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Metals and Alloys".

Deadline for manuscript submissions: closed (20 April 2024) | Viewed by 9502

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Dr. Andrzej Romański

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Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, 30 Mickiewicz Avenue, 30-059 Krakow, Poland
Interests: powder metallurgy; sintered diamond tools; diamond retention; metal matrix composites
Special Issues, Collections and Topics in MDPI journals

Dr. Maciej Sułowski

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Guest Editor

Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, 30 Mickiewicz Avenue, 30-059 Krakow, Poland
Interests: powder metallurgy (P/M); P/M structural steels; alloying elements in P/M structural steels
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The earliest large-scale industrial application of powder metallurgy (P/M) involved the production of tungsten filaments for light bulbs in the beginning of the 20th century. Since then, P/M technology has been increasingly used to manufacture a wide variety of structural parts, tools and specialty materials. Powder metallurgy has also become the method of choice for creating composites. It enables the production of materials that cannot otherwise be obtained, such as some electrical contacts (W-Cu, W-Ag, Cr-Cu and Cu-C), cemented carbides (WC-Co and WC-TiC-Co), self-lubricant bearings, filters and flame arrestors, metal matrix friction materials, magnets, etc. More recent developments in P/M processing techniques such as warm compaction, hot isostatic pressing, powder injection molding and additive manufacturing, to name a few, provide an opportunity to fabricate high-density materials and complex-shaped parts that are difficult to form or machine by conventional methods. Therefore, this Special Issue is addressed to all P/M specialists, from both industry and academia, who are willing to share knowledge about new sintered materials, their areas of application and the latest innovations in P/M processing techniques.

Dr. Andrzej Romański
Dr. Maciej Sułowski
Guest Editors

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Keywords

powder metallurgy (P/M)
P/M materials
sintered materials
pressing
sintering
infiltration
structural sintered parts
structural P/M parts
P/M tools
additive manufacturing

Published Papers (10 papers)

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Research

15 pages, 24407 KiB

Open AccessArticle

Experimental Investigation on Magnetic Abrasive Finishing for Internal Surfaces of Waveguides Produced by Selective Laser Melting

by Liaoyuan Wang, Yuli Sun, Zhongmin Xiao, Liming Yao, Jiale Guo, Shijie Kang, Weihao Mao and Dunwen Zuo

Materials 2024, 17(7), 1523; https://doi.org/10.3390/ma17071523 - 27 Mar 2024

Viewed by 459

Abstract

To enhance the surface quality of metal 3D-printed components, magnetic abrasive finishing (MAF) technology was employed for post-processing polishing. Experimental investigation employing response surface methodology was conducted to explore the impact of processing gap, rotational speed of the magnetic field, auxiliary vibration, and magnetic abrasive particle (MAP) size on the quality enhancement of internal surfaces. A regression model correlating roughness with crucial process parameters was established, followed by parameter optimization. Ultimately, the internal surface finishing of waveguides with blind cavities was achieved, and the finishing quality was comprehensively evaluated. Results indicate that under optimal process conditions, the roughness of the specimens decreased from Ra 2.5 μm to Ra 0.65 μm, reflecting a reduction rate of 74%. Following sequential rough and fine processing, the roughnesses of the cavity bottom, side wall, and convex surface inside the waveguide reduced to 0.59 μm, 0.61 μm, and 1.9 μm, respectively, from the original Ra above 12 μm. The findings of this study provide valuable technical insights into the surface finishing of metal 3D-printed components. Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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18 pages, 8792 KiB

Open AccessArticle

Processing and Properties of ZrB₂-Copper Matrix Composites Produced by Ball Milling and Spark Plasma Sintering

by Iwona Sulima and Grzegorz Boczkal

Materials 2023, 16(23), 7455; https://doi.org/10.3390/ma16237455 - 30 Nov 2023

Viewed by 639

Abstract

Copper matrix composites with zirconium diboride (ZrB₂) were synthesised by ball milling and consolidated by Spark Plasma Sintering (SPS). Characterisations of the ball-milled composite powders were performed by scanning electron microscopy (SEM), X-ray diffraction, and measurement of the particle size distribution. The effect of the sintering temperature (1123 K, 1173 K, and 1223 K) and pressure (20 MPa and 35 MPa) on the density, porosity, and Young’s modulus was investigated. The relationship between the change of Orb content and physical, mechanical, and electrical properties was studied. Experimental data showed that the properties of Cu–Orb composites depended significantly on the SPS sintering conditions. The optimal sintering temperature was 1223 K with a pressure of 35 MPa. Composites exhibited a high degree of consolidation. For these materials, the apparent density was in the range of 93–97%. The results showed that the higher content of Orb in the copper matrix was responsible for the improvement in Young’s modulus and hardness with the reduction of the conductivity of sintered composites. The results showed that Young’s modulus and the hardness of the Cu 20% Orb composites were the highest, and were 165 GPa and 174 HV0.3, respectively. These composites had the lowest relative electrical conductivity of 17%. Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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18 pages, 21482 KiB

Open AccessArticle

Microstructure and Mechanical Properties of In Situ Synthesized Metastable β Titanium Alloy Composite from Low-Cost Elemental Powders

by Krystian Zyguła, Tino Mrotzek, Oleksandr Lypchanskyi, Dariusz Zientara, Maik Gude, Ulrich Prahl and Marek Wojtaszek

Materials 2023, 16(23), 7438; https://doi.org/10.3390/ma16237438 - 29 Nov 2023

Viewed by 710

Abstract

The titanium matrix composite was produced through a hot compaction process at 1250 °C using the mixture of elemental powders with chemical composition of Ti-5Al-5Mo-5V-3Cr and 2 wt.% addition of boron carbide. The phase analysis via X-ray diffraction method was performed to confirm the occurrence of an in situ reaction between boron carbide and titanium. Then, the wide-ranging microstructural analysis was performed using optical microscopy as well as scanning electron microscopy along with energy-dispersive X-ray spectroscopy and electron backscatter diffraction. Based on this investigation, it was possible to describe the diffusion behavior during hot compaction and possible precipitation capabilities of TiC and TiB phases. Tensile and compression tests were conducted to determine the strength properties. The investigated composite has an ultimate tensile strength of about 910 ± 13 MPa with elongation of 10.9 ± 1.9% and compressive strength of 1744 ± 20 MPa with deformation of 10.5 ± 0.2%. Observation of the fracture surface allowed us to determine the dominant failure mechanism, which was crack propagation from the reaction layer surrounding remaining boron carbide particle, through the titanium alloy matrix. The study summarizes the process of producing an in situ titanium matrix composite from elemental powders and B₄C additives and emphasizes the importance of element diffusion and reaction layer formation, which contributes to the strength properties of the material. Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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11 pages, 1706 KiB

Open AccessFeature PaperArticle

The Effect of Ti/Ta Ratio and Processing Routes on the Hardness and Elastic Modulus of Porous TiNbZrTa Alloys

by Celia González-Guillén, Ghaith Al Hawajreh Kamel, Eduardo Degalez-Duran, Elizaveta Klyatskina, Muhammad Naeem, Liliana Romero-Resendiz, Gonzalo Gonzalez and Vicente Amigó Borrás

Materials 2023, 16(23), 7362; https://doi.org/10.3390/ma16237362 - 27 Nov 2023

Viewed by 871

Abstract

TiNbZrTa alloys are promising for multidisciplinary applications, such as refractory and biomedical purposes, due to their high thermal stability and non-toxicity. Hardness and elastic modulus are among the key features for their adequate industrial applications. The influence of porosity and Ti/Ta ratio were investigated on TiNbZrTa alloys produced by three different processing routes, i.e., (i) blend element and posterior press and sintering (BE + P&S); (ii) mechanical alloying with press and sintering (MA + P&S); and (iii) arc melting and casting. Porosity decreased in the following order: casting < MA + P&S < BE + P&S. The total porosity of alloys increased with increasing Ta contents, i.e., by lowering the Ti/Ta ratio. However, the Ti/Ta ratio did not considerably affect the bonding energy or the elastic modulus. Hardness was increased significantly in dense alloys compared to porous ones. However, porosity and Ti/Ta ratio did not show a clear trend in hardness among the porous alloys. Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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13 pages, 49823 KiB

Open AccessArticle

Improvement in Abrasive Wear Resistance of Metal Matrix Composites Used for Diamond–Impregnated Tools by Heat Treatment

by Elżbieta Cygan-Bączek, Sławomir Cygan, Piotr Wyżga, Pavel Novák, Ladislav Lapčák and Andrzej Romański

Materials 2023, 16(18), 6198; https://doi.org/10.3390/ma16186198 - 13 Sep 2023

Viewed by 967

Abstract

This work presents the possibilities of producing a substitute for a commercial matrix material for sintered metal–diamond tools which is characterized by increased tribological properties required in machining natural stones and concrete. In this study, the improvement in wear behavior of sintered pre-alloyed matrix caused by a thermal treatment was investigated. Several mixtures made of commercially available powders were homogenized by ball milling and consolidated at 900 °C using the spark plasma sintering (SPS) method. During cooling down, the specimens were subjected to isothermal holding at 350 or 250 °C for 1 h. After consolidation, all specimens were tested for density and hardness, whereas selected specimens were characterized by scanning electron microscopy (SEM) and flexural strength tests. The specimens made of BDCM50 powder (a mixture of the base and pre-alloyed powders in 50:50 proportion) shows excellent properties including σ_0.2 = 1045 MPa in the three-point bending test and HV10 ≈ 380. Resistance to abrasive wear evaluated in both three-body and two-body conditions in the MWT abrasion test was estimated at

A_{i 3} = 18.1 \pm 3.9

μm/20 m and

A_{i 2} = 95.9 \pm 11.8

μm/20 m, respectively. A series of diamond-impregnated specimens (segments) was also produced and tested for wear rate on abrasive concrete. The potential graphitization of the diamond grits was investigated using Raman spectroscopy and X-ray diffraction. As a reference, both the base Fe-Mn-Cu-Sn-C and commercially available Co+20%WC alloy were used to compare selected properties of the investigated materials. It has been proved that heat-treated specimens made of the base mixture modified with pre-alloyed powders are characterized by increased hardness and resistance to abrasive wear. The BDCM50 matrix has a negligible effect on diamond graphitization and shows excellent field performance, which makes it a good potential substitute for replacing Co+20%WC in sintered diamond-impregnated tools. Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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13 pages, 4252 KiB

Open AccessEditor’s ChoiceArticle

Microstructure of TiAl Capsules Processed by Electron Beam Powder Bed Fusion Followed by Post-Hot Isostatic Pressing

by Hanieh Bakhshi Farkoush, Giulio Marchese, Emilio Bassini, Alberta Aversa and Sara Biamino

Materials 2023, 16(16), 5510; https://doi.org/10.3390/ma16165510 - 08 Aug 2023

Viewed by 929

Abstract

The microstructures of intermetallic γ-titanium aluminide (TiAl) alloys are subjected to a certain degree of Al evaporation when processed by electron beam powder bed fusion (EB-PBF). The magnitude of the Al-loss is mainly correlated with the process parameters, and highly energetic parameters produce significant Al evaporation. The Al-loss leads to different microstructures, including the formation of inhomogeneous banded structures, thus negatively affecting its mechanical performance. For this reason, the current work deals with creating EB-PBFed TiAl capsules with the inner part produced using only the pre-heating step and melting parameters with low energetic parameters applying high beam speed from 5000 to 3000 mm/s. This approach is investigated to reduce the Al-loss and microstructure inhomogeneity after hot isostatic pressing (HIP). The results showed that the HIP treatment effectively densified the capsules obtaining a relative density of around 100%. After HIP, the capsules produced with the inner part melted at 3000 mm/s presented a lower area shrinkage (around 6.6%) compared to the capsules produced using only the pre-heating step in the core part (around 20.7%). The different magnitudes of shrinkage derived from different levels of residual porosity consolidated during the HIP process. The HIPed capsules exhibited the presence of previous particle boundaries (PPBs), covered by α₂ phases. Notably, applying low energetic parameters to melt the core partially eliminates the particles’ surface, thus reducing the PPBs formation. In this case, the capsules melted with low energetic parameters (3000 mm/s) exhibited α₂ concentration of 3.5% and an average size of 13 µm compared to the capsules produced with the pre-heating step in the inner part with an α₂ around 5.7% and an average size around 23 µm. Moreover, the Al-loss of the capsules was drastically limited, as determined by X-ray fluorescence (XRF) analysis. More in detail, the capsules produced with the pre-heating step reported an atomic percentage of Al of 48.75, while using low energetic melting parameters led to 48.36. This result was interesting, considering that the massive samples produced with standard parameters (so more energetic ones) revealed atomic Al percentage from 48.04 to 47.70. Finally, the recycled small particles showed a higher fraction of α₂ phases with respect to the coarse particles, as determined by X-ray diffraction (XRD). Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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13 pages, 7333 KiB

Open AccessArticle

Parametric Study of Planetary Milling to Produce Cu-CuO Powders for Pore Formation by Oxide Reduction

by Julian E. Tse Lop Kun, Adam P. Rutherford, Ryan S. Learn and Mark A. Atwater

Materials 2023, 16(15), 5407; https://doi.org/10.3390/ma16155407 - 01 Aug 2023

Cited by 2 | Viewed by 939

Abstract

Powder-based methods that are used to make porous metals are relatively simple and scalable, and porosity can be controlled by interparticle spacing as well as the addition of a sacrificial template. A relatively new process based on reducing oxides in a metal matrix has been demonstrated to produce microscale porosity within individual powder particles and thereby may be used to enhance other powder metal techniques. Templating methods require relatively large quantities of powder, but oxide-reduction feedstock powders have only been produced by small-batch ball milling processes (e.g., 10 s of grams). Planetary ball milling is capable of processing larger quantities of powder (e.g., 100 s of grams) but has significantly different milling characteristics. To successfully apply this technique, it was systematically studied in terms of composition, milling conditions, and the addition of stearic acid to control powder size and morphology along with final porosity. It was found that by controlling basic parameters, such as oxide levels and milling time, a relatively high porosity (25%) and powder percentage (99%) can be achieved in Cu-2 mol% CuO with only 0.035 wt% stearic acid and only 90 min of milling. Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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12 pages, 7291 KiB

Open AccessEditor’s ChoiceArticle

Strengthening Mechanisms and Retention Properties of Sintered Iron-Based Matrix Material for Metallic-Diamond Tools

by Elżbieta Cygan-Bączek and Andrzej Romański

Materials 2023, 16(15), 5307; https://doi.org/10.3390/ma16155307 - 28 Jul 2023

Viewed by 854

Abstract

This work presents the analysis of mechanisms controlling the deformation strengthening of the surface during abrasion and their impact on structural changes and mechanical properties of Fe-Mn-Cu-Sn-C matrix material, which was prepared by means of powder metallurgy (PM). The powder mixture was ball-milled for 8 h and densified to <1% porosity using hot pressing at 900 °C and 35 MPa. Phases and structural transformations taking place in austenite during plastic deformation were identified. The participation, distribution, and morphology of the phases, as well as the physicomechanical properties of the matrix material, were tested. It has been shown that during grinding, deformation twins are generated in areas where an austenitic microstructure is present. To test the ability of the matrix to keep diamond crystals firmly cylindrical (Ø11.3 mm× 5 mm), diamond-impregnated specimens containing diamond grits of 30/40 mesh in size and at a concentration of 20 (5% vol.) were prepared. It was finally determined by the diamond-retention index, which is the number of retained diamond particles compared to the total number of diamond particles and the pullouts on the working surface of the segment. This research shows that materials containing Ti- and Si-coated diamond particles, deposited by the CVD method, have the highest abrasion resistance and, therefore, have the best retention properties. In order to determine the bonding mechanism at the matrix–diamond interface, specimens were also analyzed by SEM and TEM. Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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11 pages, 3102 KiB

Open AccessArticle

Effect of Mn on the Properties of Powder Metallurgy Ti-2.5Al-xMn Alloys

by Yousef Alshammari, Shaira Mendoza, Fei Yang and Leandro Bolzoni

Materials 2023, 16(14), 4917; https://doi.org/10.3390/ma16144917 - 10 Jul 2023

Cited by 1 | Viewed by 721

Abstract

Titanium alloys are the ideal material for a wide range of structural applications, but their high cost compared to other metals hinders their adoption. Powder metallurgy and cheap alloying elements can be used to create new Ti alloys. In this study, the simultaneous addition of Al and Mn is considered to manufacture and characterise ternary Ti-2.5Al-Mn alloys obtained via pressing and sintering by varying the Mn content (1–10 wt.%). It is found that the addition of the alloying elements reduces compressibility. Consequently, the amount of porosity increases (8.5 → 10.8%) with the amount of Mn as the alloys were processed under the same conditions. The progressive addition of Mn refines the classical lamellar microstructure and, eventually, transforms it into an equiaxed β-grain structure with acicular α grains. The microstructural changes lead to continuous increases in strength (ultimate tensile strength: 694 → 851 MPa) and hardness (225 → 325 HV30) with an associated loss of ductility (elongation to failure: 13.9 → 1.0%). However, the obtained ternary Ti-2.5Al-Mn alloys have similar or better overall mechanical behaviour than most of the binary Ti-Mn alloys obtained through a variety of manufacturing methods. Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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15 pages, 5859 KiB

Open AccessEditor’s ChoiceArticle

Influence of Alumina Grade on Sintering Properties and Possible Application in Binder Jetting Additive Technology

by Maciej Kwiatkowski, Joanna Marczyk, Piotr Putyra, Michał Kwiatkowski, Szymon Przybyła and Marek Hebda

Materials 2023, 16(10), 3853; https://doi.org/10.3390/ma16103853 - 19 May 2023

Cited by 3 | Viewed by 1588

Abstract

Alumina is one of the most popular ceramic materials widely used in both tooling and construction applications due to its low production cost, and high properties. However, the final properties of the product depend not only on the purity of the powder, but also, e.g., on its particle size, specific surface area, and the production technology used. These parameters are particularly important in the case of choosing additive techniques for the production of details. Therefore, the article presents the results of comparing five grades of Al₂O₃ ceramic powder. Their specific surface area (via Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods), particle size distribution, and phase composition by X-ray diffraction (XRD) were determined. Moreover, the surface morphology was characterized by the scanning electron microscopy (SEM) technique. The discrepancy between generally available data and the results obtained from measurements has been indicated. Moreover, the method of spark plasma sintering (SPS), equipped with the registration system of the position of the pressing punch during the process, was used to determine the sinterability curves of each of the tested grades of Al₂O₃ powder. Based on the obtained results, a significant influence of the specific surface area, particle size, and the width of their distribution at the beginning of the Al₂O₃ powder sintering process was confirmed. Furthermore, the possibility of using the analyzed variants of powders for binder jetting technology was assessed. The dependence of the particle size of the powder used on the quality of the printed parts was demonstrated. The procedure presented in this paper, which involves analyzing the properties of alumina varieties, was used to optimize the Al₂O₃ powder material for binder jetting printing. The selection of the best powder in terms of technological properties and good sinterability makes it possible to reduce the number of 3D printing processes, which makes it more economical and less time-consuming. Full article

(This article belongs to the Special Issue Recent Application of Powder Metallurgy Materials)

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