Product Development in Net-Shape Metal Powder Technologies

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Powder Metallurgy".

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 8505

Special Issue Editors

Department of Industrial Engineering, Universita degli Studi di Trento, 38123 Trento, Italy
Interests: design methods for powder metallurgy; pressing and sintering; binder jetting; powder behavior in compaction; dimensional change on sintering; geometrical tolerances application and verification
Department of Mechanical Engineering, Politecnico di Milano, Milan, Italy
Interests: Binder jetting; Functional sintered ceramics; Sintering; Microstructural characterization of metals and alloys; Surface treatments and wear; Shape memory alloys
Department of Industrial Engineering, University of Trento, Trento, Italy
Interests: mechanical design; structural mechanics; strength of materials; finite element modeling; fatigue; fracture mechanics; biomechanics
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Special Issue Information

Dear Colleagues,

Metal powder net-shape and near net-shape technologies are increasingly generating interest, as they allow producing parts as close as possible to their final shape, eliminating or reducing secondary operations, and consequently reducing scrap, costs, time to market, and the environmental impact. Among them, press and sinter, metal injection molding, and recently, metal additive manufacturing are attractive to a huge market. Nevertheless, the specific characteristics of such technologies must be carefully considered, aiming at best exploiting the benefits. The well-known product development process, which implies the consideration of the synergistic influence of the material, shape and production process in a collaborative environment, is a crucial and difficult task when dealing with such technologies. Metal powders for conventional powder metallurgy strongly differ from metal powders for additive manufacturing, and their characteristics may dramatically affect the properties of final parts. The inappropriate definition of the process parameters inevitably introduces defects in the part at a geometric and microstructural level that detrimentally affect its functioning in operation and its structural reliability. The shape of products must be optimized according to the peculiarities of the technology. Moreover, aiming at obtaining parts as close as possible to their final shape, dimensional and geometrical control is a crucial aspect to be considered in the design step. Depending on the technology, the designer must consider the influence of many different variables, both related to modeling platforms and to process parameters. In addition, the parameters of the metallurgical process must be carefully defined, since they strongly affect the final microstructure and the onset of distortions, residual stresses and different types of localized or diffuse defects.

This Special Issue invites papers concerned with product development in net-shape and near net-shape metal powder technologies from different points of view, considering the whole life-cycle of the products, and the need for collaboratively evaluating the many different variables affecting the characteristics of the final product.

Prof. Dr. Ilaria Cristofolini
Prof. Dr. Nora Lecis
Prof. Dr. Vigilio Fontanari
Guest Editors

Manuscript Submission Information

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Keywords

  • Metal powder production and characterization
  • Development of new metal powder mixes
  • Modeling architectures and knowledge-based systems
  • Topological issues and shape optimization
  • Methods and tools, considering the characteristics of the specific production processes in the different steps of the design process
  • Simulation and experimental verification of the influence of design–process parameters on the geometric, microstructural and mechanical characteristics of the final parts
  • Verification of the dimensional and geometric characteristics, by both contact and contactless techniques
  • Experimental investigation of the structural reliability of the components
  • Lifecycle and environmental concerns

Published Papers (4 papers)

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Research

19 pages, 5589 KiB  
Article
Relation between Mechanical Milling Parameters in Phase Transformation and Oxygen Content in Ti–Nb–Mo Powders for Posterior Sintering
Metals 2022, 12(8), 1238; https://doi.org/10.3390/met12081238 - 22 Jul 2022
Cited by 3 | Viewed by 1123
Abstract
The influence of open vessels during milling for 12, 24, 40 and 60 h on microstructure homogeneity and oxygen content effect in the β Ti–Nb–Mo system microstructure were studied. The β phase increased with longer milling times and the strain hardening on particles [...] Read more.
The influence of open vessels during milling for 12, 24, 40 and 60 h on microstructure homogeneity and oxygen content effect in the β Ti–Nb–Mo system microstructure were studied. The β phase increased with longer milling times and the strain hardening on particles was verified at 60 h when agglomeration was greater and was also noticed after 40 h in the continuous mode. Oxygen content dropped slightly until 40 h and increased after 60 h, a result linked with the observed hardening. For 40 h in the continuous mode, the oxygen content was noted near 12 h, 24 h and 40 h with high hardness values. For the sintered parts, the α phase and oxygen content significantly increased in all samples. Microhardness-sintered samples decreased compared to sample powders due to grain growth during the sintering. Bending strength was higher at 60 h with more oxygen and α phase content. After 40 h in the continuous mode, more suitable mechanical properties were reached because hardness and bending strength were closer to bone tissue, which was associated with strain hardening and a small crystallite size. Full article
(This article belongs to the Special Issue Product Development in Net-Shape Metal Powder Technologies)
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14 pages, 5750 KiB  
Article
Analysis of the Flatness Form Error in Binder Jetting Process as Affected by the Inclination Angle
Metals 2022, 12(3), 430; https://doi.org/10.3390/met12030430 - 28 Feb 2022
Cited by 3 | Viewed by 1945
Abstract
Binder jetting (BJ) has demonstrated high competitiveness among additive manufacturing processes on account of its high production rate at a low material cost. However, both the design procedure and the process for BJ have to be further developed, aiming towards the proper control [...] Read more.
Binder jetting (BJ) has demonstrated high competitiveness among additive manufacturing processes on account of its high production rate at a low material cost. However, both the design procedure and the process for BJ have to be further developed, aiming towards the proper control of the geometrical and dimensional precision and accuracy of the final product. This paper aims to study the factors that affect the flatness form error. Five geometries were designed to obtain planes that were inclined with respect to the fabrication direction. These planes were measured by a coordinate measuring machine in both the green and sintered state, deriving the best-fitting plane and the flatness form error. The analysis of the green samples demonstrates the prevailing influence of saturation level and layer shifting on flatness form error. In the sintered parts, a dimensional change in sintering can determine shape distortion, or an increment in the surface irregularity observed in the green state. The experimental results clearly evidence the effect of both printing and sintering on the quality of the final product, which should be considered when designing parts to be produced using BJ technology. Full article
(This article belongs to the Special Issue Product Development in Net-Shape Metal Powder Technologies)
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11 pages, 5216 KiB  
Article
Coarsening Kinetics of Y2O3 Dispersoid in New Grade of Fe-Al-Cr-Based ODS Alloy
Metals 2022, 12(2), 210; https://doi.org/10.3390/met12020210 - 23 Jan 2022
Cited by 7 | Viewed by 2034
Abstract
Oxide dispersion strengthened (ODS) alloys with a high content of Al are candidate materials for extreme high temperature applications such as turbine blades and other components working at temperatures significantly above 1000 °C. While oxidation kinetics of Fe–Al ODS steels is frequently studied, [...] Read more.
Oxide dispersion strengthened (ODS) alloys with a high content of Al are candidate materials for extreme high temperature applications such as turbine blades and other components working at temperatures significantly above 1000 °C. While oxidation kinetics of Fe–Al ODS steels is frequently studied, the stability and growth kinetics of strengthening oxide dispersion is a rarely studied topic. The Fe-10Al-4Cr-4Y2O3 is an experimental material, fabricated at IPM by powder metallurgy route and contains much higher volume fraction of Y2O3 than similar materials. Stability and growth kinetics of Y2O3 particles of our material are studied on 24 samples aged for 0.5, 1, 2, 4, 8, 16, 32 and 72 h at 1200 °C, 1300 °C and 1400 °C. The sizes of at least 600 individual Y2O3 particles are measured on each sample to obtain extensive statistical analysis of the particle growth. The average particle size coarsens from 28.6 ± 0.7 nm to 36.9 ± 0.9 nm in 1200 °C series and to 81.4 ± 5.6 nm in 1400 °C series. The evaluated activation energy of coarsening of Y2O3 particles is 274 ± 65 kJ. The effects of particle coarsening on mechanical properties is demonstrated by HV measurements, which is in very good agreement with the Orowan theory. Full article
(This article belongs to the Special Issue Product Development in Net-Shape Metal Powder Technologies)
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13 pages, 4521 KiB  
Article
Effect of Process Parameters on the Surface Microgeometry of a Ti6Al4V Alloy Manufactured by Laser Powder Bed Fusion: 3D vs. 2D Characterization
Metals 2022, 12(1), 106; https://doi.org/10.3390/met12010106 - 05 Jan 2022
Cited by 6 | Viewed by 2373
Abstract
The influence of the main process parameters, laser power, point distance and time exposure, on the surface microgeometry of Ti6Al4V specimens produced by a pulsed powder bed fusion process was investigated. A 3D characterization was carried out and collected data were elaborated to [...] Read more.
The influence of the main process parameters, laser power, point distance and time exposure, on the surface microgeometry of Ti6Al4V specimens produced by a pulsed powder bed fusion process was investigated. A 3D characterization was carried out and collected data were elaborated to reconstruct the surface and to determine both the 3D and the 2D material ratio curves along different directions. The 3D material ratio curve gives a slightly lower material ratio of peak zone Mr1 and higher material ratio of valley zone Mr2, reduced peak height Rpk and reduced valley height Rvk than the 2D curves. Roughness is greater in the 3D analysis than in the 2D one, skewness is the same and kurtosis increases from <3 in 2D to >3 in 3D. Roughness and skewness increase on increasing point distance and decreasing time exposure and laser power. Within the investigated ranges (27.3–71.2 J/mm3), an increase in energy density reduces the surface roughness while skewness and kurtosis are not significantly affected. The results indicate that a 3D approach allows better characterization of the surface microgeometry than a 2D one. Full article
(This article belongs to the Special Issue Product Development in Net-Shape Metal Powder Technologies)
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