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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (30 October 2021) | Viewed by 27563

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Prof. Dr. Rafał Świercz

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Institute of Manufacturing Technology, Faculty of Production Engineering, Warsaw University of Technology, Narbutta 85, 02-524 Warsaw, Poland
Interests: electrical discharge machining; noncoventional technology; surface finishing technology; surface metrology; characteristics of material properties; nanomaterials; experimental and simulative analysis of manufacturing processes; optimization of manufacturing processes
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Special Issue Information

Dear Colleagues,

The progress of materials engineering has resulted in the introduction of new materials suitable for selected industries. The development of proper machining methods for modern materials, for example, is critically important for their implementation in the aerospace, automobile or machinery industries. In recent years, the involvement of multidisciplinary teams in the application of nonconventional technology, including electrical discharge machining, electrochemical machining, additive manufacturing, abrasive finishing, hybrid manufacturing, or laser processing, in the precision manufacturing of difficult-to-cut material has considerably increased.
The main aim of this Special Issue is to present recent advances in the field of nonconventional technology of materials processing.
This Special Issue includes high-quality original research papers, review papers, and case studies dealing with the investigation, modeling, optimization, and simulation of nonconventional technology of materials processing.
It is my pleasure to invite you to submit original research papers, short communications, and state-of-the-art reviews for this Special Issue.

Dr. Rafał Świercz
Guest Editor

Manuscript Submission Information

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Keywords

Nonconventional manufacturing processes
Electrical discharge machining
Electrochemical machining
Abrasive finishing
Modelling and simulation
Optimization
Additive manufacturing

Published Papers (12 papers)

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Research

18 pages, 7408 KiB

Open AccessArticle

Analysis of the Innovative Channel Strut Concept Manufactured by Roll-Forming

by Andrzej Kochański, Piotr Czyżewski, Robert Cacko and Mariusz Roznowski

Materials 2022, 15(3), 1107; https://doi.org/10.3390/ma15031107 - 31 Jan 2022

Viewed by 2230

Abstract

Due to the wide use of channel strut components, manufacturing is implemented in many industrial plants. Standard technology of profiles is based on welding of two parts of the profile and requires the regalvanizing of the joint zone causes. Thus, the production is challenging to automate on a single line. The main idea of the article is to present a concept of a channel strut, a cold-formed continuous metal component with an open or closed profile section. It would serve as a cantilever support instead of a standard solution. In the article, a unique lock system combination is proposed and analyzed both numerically and experimentally to provide steadiness of the strut without welding or other joining techniques. Two main lock shapes—semicircular and triangle—were proposed with some variations in the cutting plane. Analyses were carried out for three main profile cross-sections with different dimensions, based on the current industrial applications. The semicircular type of the lock was found to be the most stable, giving optimal strength to the strut under assumed loading, comparable to traditional solutions. The commercial FEM software MSC Marc was used for the numerical analysis. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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11 pages, 4018 KiB

Open AccessArticle

Preliminary Study of the Rhenium Addition on the Structure and Mechanical Properties of Tungsten Heavy Alloy

by Paweł Skoczylas and Mieczysław Kaczorowski

Materials 2021, 14(23), 7365; https://doi.org/10.3390/ma14237365 - 30 Nov 2021

Cited by 4 | Viewed by 1745

Abstract

The results of structure and mechanical property investigations of tungsten heavy alloy (THA) with small additions of rhenium powder are presented. The material for the study was prepared using liquid phase sintering (LPS) of mixed and compacted powders in a hydrogen atmosphere. From the specimens, the samples for mechanical testing and structure investigations were prepared. It follows from the results of the microstructure observations and mechanical studies, that the addition of rhenium led to tungsten grain size decreasing and influencing the mechanical properties of W-Ni-Fe-Co base heavy alloy. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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24 pages, 3687 KiB

Open AccessArticle

Microstructure of Rhenium Doped Ni-Cr Deposits Produced by Laser Cladding

by Paweł Kołodziejczak, Dariusz Golański, Tomasz Chmielewski and Marcin Chmielewski

Materials 2021, 14(11), 2745; https://doi.org/10.3390/ma14112745 - 22 May 2021

Cited by 21 | Viewed by 2360

Abstract

The addition of Rhenium up to 6% to Ni-Cr alloys can dramatically improve the corrosion and oxide resistance of deposited coatings at high operating temperatures. Ni-Cr+Re layers can be successfully produced using conventional powder metallurgy, high rate solidification (HRS), or magnetron sputtering methods. However, in industrial applications, high-performance deposition methods are needed, e.g., laser cladding. Laser cladding has several advantages, e.g., metallurgical bonding, narrow heat-affected zone (HAZ), low dilution, and slight thermal damage to the substrate. In this paper, a powder Ni-Cr composite with 1% (wt.) of Rhenium was produced, then deposited onto a steel substrate (16Mo3) by laser cladding to assess the micro and macrostructural properties of the obtained layers. Besides the macro and microscopic observations, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) microanalysis of the deposit and HAZ as well as microhardness measurements have been conducted. The microstructure observations revealed four subareas of HAZ gradually changing from the fusion line towards the base material. Maximum hardness occurred in the HAZ, mainly in areas closer to the clad/substrate interface, reaching up to 350–400 HV. No sudden changes in the composition of the deposit and the area of fusion line were observed. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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24 pages, 22780 KiB

Open AccessArticle

Selected Aspects of Electrochemical Micromachining Technology Development

by Sebastian Skoczypiec, Piotr Lipiec, Wojciech Bizoń and Dominik Wyszyński

Materials 2021, 14(9), 2248; https://doi.org/10.3390/ma14092248 - 27 Apr 2021

Cited by 11 | Viewed by 1853

Abstract

The paper focuses on the fundamentals of electrochemical machining technology de-elopement with special attention to applications for micromachining. In this method, a material is removed during an anodic electrochemical dissolution. The method has a number of features which make it attractive technology for shaping parts with geometrical features in range of micrometres. The paper is divided into two parts. The first one covers discussion on: general characteristics of electrochemical machining, phenomena in the gap, problems resulting from scaling down the process and electrochemical micromachining processes and variants. The second part consists of synthetic overview of the authors’ research on localization of pulse electrochemical micromachining process and case studies connected with application of this method with use of universal cylindrical electrode-tool for shaping cavities in 1.4301 stainless steel. The latter application was conducted in two following variants: electrochemical contour milling and shaping carried out with sidewall surface of rotating tool. In both cases, the obtained shape is a function of electrode tool trajectory. Selection of adequate machining strategy allows to obtain desired shape and quality. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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19 pages, 5902 KiB

Open AccessArticle

Microstructural Investigation of a Friction-Welded 316L Stainless Steel with Ultrafine-Grained Structure Obtained by Hydrostatic Extrusion

by Beata Skowrońska, Tomasz Chmielewski, Mariusz Kulczyk, Jacek Skiba and Sylwia Przybysz

Materials 2021, 14(6), 1537; https://doi.org/10.3390/ma14061537 - 21 Mar 2021

Cited by 21 | Viewed by 2208

Abstract

The paper presents the microstructural investigation of a friction-welded joint made of 316L stainless steel with an ultrafine-grained structure obtained by hydrostatic extrusion (HE). Such a plastically deformed material is characterized by a metastable state of energy equilibrium, increasing, among others, its sensitivity to high temperatures. This feature makes it difficult to weld ultra-fine-grained metals without losing their high mechanical properties. The use of high-speed friction welding and a friction time of <1 s reduced the scale of the weakening of the friction joint in relation to result obtained in conventional rotary friction welding. The study of changes in the microstructure of individual zones of the friction joint was carried out on an optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron backscattered diffraction (EBSD) analysis system. The correlation between the microstructure and hardness of the friction joint is also presented. The heat released during the high-speed friction welding initiated the process of dynamic recrystallization (DRX) of single grains in the heat-affected zone (HAZ). The additional occurrence of strong plastic deformations (in HAZ) during flash formation and internal friction (in the friction weld and high-temperature HAZ) contributed to the formation of a highly deformed microstructure with numerous sub-grains. The zones with a microstructure other than the base material were characterized by lower hardness. Due to the complexity of the microstructure and its multifactorial impact on the properties of the friction-welded joint, strength should be the criterion for assessing the properties of the joint. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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19 pages, 10148 KiB

Open AccessEditor’s ChoiceArticle

The Accuracy of Finishing WEDM of Inconel 718 Turbine Disc Fir Tree Slots

by Jan Burek, Robert Babiarz, Jarosław Buk, Paweł Sułkowicz and Krzysztof Krupa

Materials 2021, 14(3), 562; https://doi.org/10.3390/ma14030562 - 25 Jan 2021

Cited by 18 | Viewed by 2976

Abstract

Servicing aircraft engines sometimes requires manufacturing only a single piece of a given part. Manufacturing a turbine disc using traditional methods is uneconomical. It is necessary to use a different machining method recommended for small lot production. One of the proposed methods is WEDM (wire electrical discharge machining). The article presents the results of the research on finishing WEDM of Inconel 718 turbine disc fir tree slots. The influence of infeed, mean gap voltage, peak current, pulse off-time, and discharge energy on the shape accuracy, surface roughness, microcracks, and the white layer thickness were determined. Mathematical models were developed based on the DoE (Design of Experiment) analysis. The statistical significance of the models was verified with the ANOVA (Analysis of Variance) test. The machining parameters control methods that allow achieving the required shape accuracy, surface roughness, and surface layer condition were presented. The obtained surface roughness was Ra = 0.84 μm, the shape accuracy of the slot in the normal-to-feed direction was Δd = 0.009 μm, the profile shape accuracy was Δr = 0.033 μm, and the thickness of recast (white) layer was approximately 5 μm. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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24 pages, 7493 KiB

Open AccessArticle

Advanced Structural and Technological Method of Reducing Distortion in Thin-Walled Welded Structures

by Piotr Horajski, Lukasz Bohdal, Leon Kukielka, Radoslaw Patyk, Pawel Kaldunski and Stanislaw Legutko

Materials 2021, 14(3), 504; https://doi.org/10.3390/ma14030504 - 21 Jan 2021

Cited by 7 | Viewed by 3048

Abstract

The article presents an innovative method of reducing welding distortions of thin-walled structures by introducing structural and technological changes. The accuracy of the method was demonstrated on the example of welding the stub pipes to the outer surface of a thin-walled tank with large dimensions, made of steel 1.4301 with a wall thickness of 1.5 × 10⁻³ (m). During traditional Gas Tungsten Arc Welding (GTAW), distortions of the base are formed, the flatness deviation of which was 11.9 × 10⁻³ (m) and exceeded the permissible standards. As a result of structural and technological changes, not only does the joint stiffness increase, but also a favorable stress state is introduced in the flange, which reduces the local welding stresses. Numerical models were developed using the finite element method (FEM), which were used to analyze the residual stresses and strains pre-welding, in extruded flanges, in transient, and post-welding. The results of the calculations for various flanges heights show that there is a limit height h = 9.2 × 10⁻³ (m), above which flange cracks during extrusion. A function for calculating the flange height was developed due to the required stress state. The results of numerical calculations were verified experimentally on a designed and built test stand for extrusion the flange. The results of experimental research confirmed the results of numerical simulations. For further tests, bases with a flange h = 6 × 10⁻³ (m) were used, to which a stub pipe was welded using the GTAW method. After the welding process, the distortion of the base was measured with the ATOS III scanner (GOM a Zeiss company, Oberkochen, Germany). It has been shown that the developed methodology is correct, and the introduced structural and technological changes result in a favorable reduction of welding stresses and a reduction in the flatness deviation of the base in the welded joint to 0.39 × 10⁻³ (m), which meets the requirements of the standards. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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18 pages, 5857 KiB

Open AccessArticle

Standoff Distance in Ultrasonic Pulsating Water Jet

by Madhulika Srivastava, Akash Nag, Somnath Chattopadhyaya and Sergej Hloch

Materials 2021, 14(1), 88; https://doi.org/10.3390/ma14010088 - 27 Dec 2020

Cited by 11 | Viewed by 2240

Abstract

The water hammer effect is the basis of technologies which is artificially responsible for the decay of continuous jets. A recently developed technique enhances the pressure fluctuations using an acoustic chamber, leading to enhanced erosion effects for various water volume flow rates. The optimum standoff distance for an ultrasonic enhanced water jet is not appropriately estimated using an inclined trajectory. The objective of this study is to comprehend the true nature of the interaction of the standoff distance following the stair trajectory and traverse speed of the nozzle on the erosion depth. Additionally, it also critically compares the new method (staircase trajectory) that obeys the variation in frequency of the impingements for defined volume flow rates with the inclined trajectory. In this study, at constant pressure (p = 70 MPa), the role of impingement distribution with the variation of traverse speed (v = 5–35 mm/s) along the centerline of the footprint was investigated. The maximum erosion depth corresponding to each traverse speed is observed at approximately same standoff distance (65 ± 5 mm) and decreases with the increment in traverse speed (h = 1042 and 47 µm at v = 5 and 35 mm/s, respectively). The results are attributed to the variation in the number of impingements per unit length. The surface and morphology analysis of the cross-section using SEM manifested the presence of erosion characteristics (micro-cracks, cavities, voids, and upheaved surface). By varying the water cluster, different impingement densities can be achieved that are suitable for technological operations such as surface peening, material disintegration, or surface roughening. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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15 pages, 8956 KiB

Open AccessArticle

Application of the Numerical Model to Design the Geometry of a Unit Tool in the Innovative RTH Hydroforming Technology

by Hanna Sadłowska, Andrzej Kochański and Magdalena Czapla

Materials 2020, 13(23), 5427; https://doi.org/10.3390/ma13235427 - 28 Nov 2020

Cited by 3 | Viewed by 1421

Abstract

The article presents a newly patented rapid tube hydroforming (RTH) manufacturing method, perfectly suited to single-piece production. The RTH technology significantly complements the scope of hydroforming processes. Due to the unusual granular material of the die tool, in particular moulding sand or mass, the process design requires the use of numerical modelling calculations. This is related to the complexity and the synergistic effect of process parameters on the final shape of the product. The work presents the results of numerical modelling studies of the process, including the behaviour of the die material and the material of the hydroformed profile. The numerical calculations were performed for a wide range of parameters, and can be used in various applications. The significant properties of moulding material used for the RTH tests were determined and one was chosen to build the die in RTH experiments. The results of the numerical modelling were compared with the results of the experiments, which proved their high compatibility. The final conclusions of the analyses indicate that the RTH technology has many possibilities that are worth further development and research. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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14 pages, 1639 KiB

Open AccessArticle

Surface Properties of Poly(Hydroxyurethane)s Based on Five-Membered Bis-Cyclic Carbonate of Diglycidyl Ether of Bisphenol A

by Mariusz Tryznowski and Zuzanna Żołek-Tryznowska

Materials 2020, 13(22), 5184; https://doi.org/10.3390/ma13225184 - 17 Nov 2020

Cited by 9 | Viewed by 2018

Abstract

Poly(hydroxyurethane)s (PHU) are alternatives for conventional polyurethanes due to the use of bis-cyclic dicarbonates and diamines instead of harmful and toxic isocyanates. However, the surface properties of poly(hydroxyurethane)s are not well known. In this work, we focus on the analysis of the surface properties of poly(hydroxyurethane) coatings. Poly(hydroxyurethane)s were obtained by a catalyst-free method from commercially available carbonated diglycidyl ether of bisphenol A (Epidian 6 epoxy resins) and various diamines: ethylenediamine, trimethylenediamine, putrescine, hexamethylenediamine, 2,2,4(2,4,4)-trimethyl-1,6-hexanediamine, m-xylylenediamine, 1,8-diamino-3,6-dioxaoctane, 4,7,10-trioxa-1,13-tridecanediamine, and isophorone diamine, using a non-isocyanate route. The structures of the obtained polymers were confirmed by FT-IR, ¹H NMR and ¹³C NMR spectroscopy, and thermogravimetric (TGA) and differential scanning calorimetry (DSC) analyses were performed. The rheological characteristic of the obtained polymers is presented. The static contact angles of water, diidomethane, and formamide, deposited on PHU coatings, were measured. From the measured contact angles, the surface free energy was calculated using two different approaches: Owens–Wendt and van Oss–Chaudhury–Good. Moreover, the wetting envelopes of PHU coatings were plotted, which enables the prediction of the wetting effect of various solvents. The results show that in the investigated coatings, a mainly dispersive interaction occurs. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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14 pages, 4837 KiB

Open AccessArticle

Microstructure and Properties of Tungsten Heavy Alloy Connections Formed during Sintering with the Participation of the Liquid Phase

by Paweł Skoczylas, Zbigniew Gulbinowicz and Olgierd Goroch

Materials 2020, 13(21), 4965; https://doi.org/10.3390/ma13214965 - 4 Nov 2020

Cited by 12 | Viewed by 2332

Abstract

Tungsten heavy alloys (THA) are used in the defense industry for subcaliber bullet cores due to their high density and strength. Typically methods of joining tungsten rod elements include: soldering, friction welding or threaded sleeve splicing. The properties of the joints were tested for three types of material containing 90.8, 96.2 and 98.2 wt.%. tungsten, density from 17.3 to 18.4 g/cm³ and strength range 400–1000 MPa. Combination in the liquid phase at the sintering temperature was carried out in a vacuum furnace at a temperature of 1520 °C in a hydrogen atmosphere, and tests used pairs of both identical and dissimilar materials. After that, some of the bars were subjected to additional heat treatment at 1100 °C for 3 h. The tests of the mechanical properties in the static tensile test and the measurement of impact strength showed that the obtained strength of the joints was comparable to that of the parent material. The microstructure analysis showed that the resulting joint area, while maintaining the appropriate roughness of the joined end faces of the bars, is homogeneous without areas of the solidified matrix of the joint line. Research showed that it is possible to bond under sintering conditions with the participation of a solid liquid phase of homonymous and dissimilar THA materials. The strength of joints in dissimilar materials was comparable to a tungsten heavy alloy material with lower strength in the bonded pair while homonymous materials were comparable to the original material. The test results provided a good basis for further research in which the obtained pairs of joints will be subjected to plastic working processes. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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18 pages, 9269 KiB

Open AccessArticle

A Novel Method of Supporting the Laser Welding Process with Mechanical Acoustic Vibrations

by Arkadiusz Krajewski, Grzegorz Klekot, Marcin Cybulak and Paweł Kołodziejczak

Materials 2020, 13(18), 4179; https://doi.org/10.3390/ma13184179 - 20 Sep 2020

Cited by 8 | Viewed by 1901

Abstract

The research described in this article presents a new contactless method of introducing mechanical vibrations into the base material during CO₂ laser welding of low-carbon steel. The experimental procedure boiled down to subjecting a P235GH steel pipe with a 60 mm diameter, 3.2 mm wall thickness and 500 mm length to acoustic signals with a resonant frequency during the welding process. Acoustic vibrations with a frequency of 1385, 110 and 50 Hz were introduced into the pipe along the axis and transversely from the outer surface. The obtained welds were then subjected to structural tests and Vickers hardness measurements. The results of comparative tests show the impact of such introduced vibrations on the granular structure of the welds, as well as on their microhardness in specific areas, such as the face, penetration depth and the heat-affected zone. The effectiveness of the proposed method of introducing vibrations in the scope of grain size and shape as well as changes in the hardness distribution in the obtained welds is demonstrated. Full article

(This article belongs to the Special Issue Nonconventional Technology in Materials Processing)

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