Editorial

4 pages, 219 KiB

Open AccessEditorial

Additive Manufacturing of Metallic Components for Hard Coatings

by Ainhoa Riquelme Aguado, Carmen Sánchez de Rojas Candela and Pilar Rodrigo Herrero

Coatings 2022, 12(7), 1007; https://doi.org/10.3390/coatings12071007 - 17 Jul 2022

Cited by 1 | Viewed by 1239

Metals additive manufacturing is a new concept of fabrication that consists of depositing material layer-by-layer in a very precise and automatized way [...] Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings)

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21 pages, 20491 KiB

Open AccessArticle

The Effect of Heat Treatment on the Microstructure and Mechanical Properties of Plasma-Cladded CoCrFeNiMn Coatings on Compacted Graphite Iron

by Bo Zhang, Ruitao Fu, Peihu Gao, Baiyang Chen, Anton Naumov, Fei Li, Daming Zhao, Zhong Yang, Yongchun Guo, Jianping Li, Lei Cheng, Jinyuan Gong, Jiawei Liu and Yu Li

Coatings 2024, 14(4), 374; https://doi.org/10.3390/coatings14040374 - 22 Mar 2024

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Abstract

CoCrFeNiMn high-entropy alloy coatings were deposited on compacted graphite iron (CGI) by plasma transfer arc cladding to strengthen and improve the wear resistance (performance) of the surface. The effects of different heat treatment processes on the microstructure and mechanical properties of the CoCrFeNiMn [...] Read more.

CoCrFeNiMn high-entropy alloy coatings were deposited on compacted graphite iron (CGI) by plasma transfer arc cladding to strengthen and improve the wear resistance (performance) of the surface. The effects of different heat treatment processes on the microstructure and mechanical properties of the CoCrFeNiMn coatings were investigated. Compared with the deposited coating, the single FCC phase in the heat-treated coatings was retained, the grain size of the columnar dendrites decreased, the spacing between the dendrites increased, and the Cr-rich precipitated phase in the grain boundary increased. The heat treatment process had a positive influence on the microhardness and wear resistance of the coatings. The microhardness of the coatings increased after heat treatment. After heat treatment at 660 °C for 90 min, the coating had the highest microhardness of 563 ± 6.9 HV_0.2, and it had the best wear resistance. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings)

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14 pages, 7220 KiB

Open AccessArticle

A One-Step Novel Method to Fabricate Multigrade Ti6Al4V/TiN Composites Using Laser Powder Bed Fusion

by Carmen Sánchez de Rojas Candela, Ainhoa Riquelme, Pilar Rodrigo, Victoria Bonache, Javier Bedmar, Belén Torres and Joaquín Rams

Coatings 2024, 14(1), 90; https://doi.org/10.3390/coatings14010090 - 09 Jan 2024

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Abstract

Ti6Al4V is the most used alloy for implants because of its excellent biocompatibility; however, its low wear resistance limits its use in the biomedical industry. The additive manufacturing (AM) of Ti6Al4V is a well-established technique that is being used in many fields. However, [...] Read more.

Ti6Al4V is the most used alloy for implants because of its excellent biocompatibility; however, its low wear resistance limits its use in the biomedical industry. The additive manufacturing (AM) of Ti6Al4V is a well-established technique that is being used in many fields. However, the AM of Ti6Al4V composites is currently under investigation, and its manufacture using laser powder bed fusion (L-PBF) would result in a great benefit for many industries. The one-step novel concept proposed uses a gas-controlled L-PBF system that enables the AM of layers with different compositions. Six millimeter-edged cubes of Ti6Al4V were manufactured in an Ar atmosphere and coated with in situ Ti6Al4V/TiN layers by using an Ar–N₂ mixture given the direct reaction between titanium and nitrogen. Unreinforced Ti6Al4V presented a martensitic microstructure, and TiN reinforcement dendrites and a minor Ti₂N phase were gradually introduced into an α + β basketweave titanium matrix. The composites’ microhardness, nanohardness, and elastic modulus were 2, 3, and 1.5 times higher, respectively, than those of the Ti6Al4V. Porosity levels (caused by a lack of fusion, trapping gases, and interdendritic porosity), ranged from 7 to 12% (most measured 20–40 µm) and increased with the reinforcement content (15 to 25%). A scaled-up, proof-of-concept design of a hip implant stem was 3D printed using this nitriding method. Since the neck of the stem (top part) is more susceptible to the fracture and fretting corrosion process, the resulting graded material part consisted of unreinforced Ti6Al4V at the bottom and Ti6Al4V/TiN at the top. This change was controlled by gradually adding nitrogen to the atmosphere; moreover, it was found that the more nitrogen in the chamber, the more TiN reinforcement formed in the part. A microhardness of ~450 HV_0.1 was measured at the bottom and gradually increased to ~900 HV_0.1, with the increment corresponding to the in situ TiN reinforcement amount. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings)

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13 pages, 5344 KiB

Open AccessArticle

The Effect of an Ultrasonic Field on the Microstructure and Tribological Behavior of ZrB₂/ZrC+Ni60A/WC Composite Coating Applied by Laser Cladding

by Zhongbin Wei, Abolhassan Najafi, Morteza Taheri, Farzad Soleymani, Neda Didehvar and Gholamreza Khalaj

Coatings 2023, 13(11), 1928; https://doi.org/10.3390/coatings13111928 - 11 Nov 2023

Cited by 6 | Viewed by 810

Abstract

Ni60A/WC composite coating reinforced with ZrB₂/ZrC was layered on GTD-111 superalloy by laser cladding. The effect of an ultrasonic field on coating formation, microstructure, microhardness, and wear was investigated and analyzed. The results showed that the resulting coating had pores and [...] Read more.

Ni60A/WC composite coating reinforced with ZrB₂/ZrC was layered on GTD-111 superalloy by laser cladding. The effect of an ultrasonic field on coating formation, microstructure, microhardness, and wear was investigated and analyzed. The results showed that the resulting coating had pores and microcracks, which were removed when using an ultrasonic field. Ultrasonic fields increased the heat input and increased the dimensions of the coating pool by creating a cavitation effect. The dendrites of the coating microstructure were mainly composed of Zr(B, C) and ZrC blocks and small α-Zr dendrites. The mechanical vibrations resulting from the application of ultrasonic fields caused the crushing of the growing dendrites, and as a result, the grains and dendrites crumbled. By decreasing the grain size, the average hardness increases from 312 HV for coating without an ultrasonic field to 617 HV for coating with 300 W ultrasonic power. The results of the wear test also showed that the sample coated with 300 W of ultrasonic power, with a coefficient of friction of 0.41 and scar wear of 6.8 µm, has the highest wear resistance due to the removal of porosity and the presence of equiaxed grains on the top and bottom of the clad zone. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings)

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11 pages, 3128 KiB

Open AccessArticle

Thermoformable Conductive Compositions for Printed Electronics

by Seyed Ismail Seyed Shahabadi, Joel Ming Rui Tan and Shlomo Magdassi

Coatings 2023, 13(9), 1548; https://doi.org/10.3390/coatings13091548 - 04 Sep 2023

Cited by 1 | Viewed by 964

Abstract

The development of three-dimensional printed electronics has garnered significant interest due to the ease of integration of electronic circuitry on 3D surfaces. However, it is still very challenging to achieve the desired conformability, stretchability, and adhesion of conductive pastes used for printing on [...] Read more.

The development of three-dimensional printed electronics has garnered significant interest due to the ease of integration of electronic circuitry on 3D surfaces. However, it is still very challenging to achieve the desired conformability, stretchability, and adhesion of conductive pastes used for printing on thermoformable substrates. In this study, we propose the use of novel thermoformable ink composed of copper flakes coated with silver, which enables us to prevent the oxidation of copper, instead of the commonly used silver inks. Various polymer/solvent/flake systems were investigated, resulting in thermoformable conductive printing compositions that can be sintered under air. The best inks were screen printed on PC substrates and were thermoformed using molds with different degrees of strain. The effects of the various components on the thermoforming ability and the electrical properties and morphology of the resulting 3D structures were studied. The best inks resulted in a low sheet resistivity, 100 mΩ/□/mil and 500 mΩ/□/mil before and after thermoforming at 20%, respectively. The feasibility of using the best ink was demonstrated for the fabrication of a thermoformable 3D RFID antenna on PC substrates. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings)

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10 pages, 6210 KiB

Open AccessFeature PaperArticle

Influence of Feedstock in the Formation Mechanism of Cold-Sprayed Copper Coatings

by Jui-Ting Liang, Shao-Fu Chang, Cheng-Han Wu, Shih-Hsun Chen, Che-Wei Tsai, Kuei-Chung Cheng and Kim Hsu

Coatings 2023, 13(6), 1065; https://doi.org/10.3390/coatings13061065 - 08 Jun 2023

Cited by 2 | Viewed by 839

Abstract

The aim of this article is to investigate the characterizations and formation mechanisms of cold-sprayed coatings using gas-atomized and electrolytic powders. The study highlights the importance of reaching the particles’ critical velocity for optimal deposition. The main findings reveal that the morphology and [...] Read more.

The aim of this article is to investigate the characterizations and formation mechanisms of cold-sprayed coatings using gas-atomized and electrolytic powders. The study highlights the importance of reaching the particles’ critical velocity for optimal deposition. The main findings reveal that the morphology and stacking conditions of the coatings have a significant impact on their mechanical properties. Coatings made with gas-atomized powders exhibited noticeable pores and higher plastic deformation, while electrolytic powder coatings had greater density and smoother interfaces with the substrate. Adhesion strength relied on the physical bonding resulting from the plastic deformation energy between the spraying powders and the substrate. Gas-atomized powders showed higher adhesion compared to electrolytic powders, with dendritic powders resulting in lower adhesion due to dispersed impact force. The interaction between thermal and kinetic energy during the cold spraying process facilitated plastic deformation and particle deposition by softening and eroding the substrate surface. Insufficient plastic deformation with dendritic powders led to incomplete overlap, pore formation at the interface, and the persistence of the oxide layer along powder boundaries. Overall, these findings provide valuable insights into the influence of powder properties on coating morphology, adhesion strength, and overall performance, contributing to the understanding and optimization of cold spray processes. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings)

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17 pages, 8348 KiB

Open AccessArticle

Microstructure of NbMoTaTiNi Refractory High-Entropy Alloy Coating Fabricated by Ultrasonic Field-Assisted Laser Cladding Process

by Song Zhao, Morteza Taheri, Kourosh Shirvani, Mehdi Naserlouei, Khashayar Beirami, Moslem Paidar and Wei Sai

Coatings 2023, 13(6), 995; https://doi.org/10.3390/coatings13060995 - 26 May 2023

Cited by 10 | Viewed by 1334

Abstract

Refractory high-entropy alloys (RHEAs) contain alloying elements with a high melting point, promising high-temperature applications due to their unique properties. In this work, laser cladding is used to prepare RHEA_S based on NbMoTaTiNi. At the same time as laser cladding, the ultrasonic [...] Read more.

Refractory high-entropy alloys (RHEAs) contain alloying elements with a high melting point, promising high-temperature applications due to their unique properties. In this work, laser cladding is used to prepare RHEA_S based on NbMoTaTiNi. At the same time as laser cladding, the ultrasonic field is used, and then the microstructural characteristics, grain size, residual stress, wear, and hardness of the coating are evaluated. The results show that the coating is biphasic and includes the γ (Ni) and NbMoTaTiNi phase. The NbMoTaTiNi phase had a uniform distribution throughout the coating when the ultrasonic field was applied, so that when the ultrasonic field was not used, the NbMoTaTiNi powder, in addition to spreading uniformly, had the un-melting of large particles. This caused an increase in the residual tension of the coating. The conversion of columnar grains to the equiaxed, and the reduction in structural defects, were other characteristics of using the ultrasonic field. The formation of equiaxed grains with zigzag grain boundaries reduced the friction coefficient, wear volume loss, and the wear rate of the coating applied with ultrasonic. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings)

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9 pages, 4638 KiB

Open AccessArticle

Direct Inkjet Printing of Digitally Designed 2D TiN Patterns

by Joaquin Yus, Juan Antonio Escribano, Antonio Javier Sanchez-Herencia, Carmen Galassi and Begoña Ferrari

Coatings 2022, 12(6), 729; https://doi.org/10.3390/coatings12060729 - 25 May 2022

Cited by 2 | Viewed by 1395

Abstract

TiN is a non-oxidic ceramic widely employed as a hard coating material for cutting tools due to its high thermal and chemical stability. Among all 2D coating techniques, Inkjet printing (IJP) is one of the most promising for the fabrication of layers with [...] Read more.

TiN is a non-oxidic ceramic widely employed as a hard coating material for cutting tools due to its high thermal and chemical stability. Among all 2D coating techniques, Inkjet printing (IJP) is one of the most promising for the fabrication of layers with customized designs. However, despite its advantages, this process has not been used so far with this material. In this work, we prepared TiN suspensions for their implementation in IJP with a nozzle of 70 μm. A complete study of the ink properties was performed to formulate a suitable ink with a high level of dispersion and to evaluate the jetting during the printing process. Moreover, after a sintering process at 1100 °C under vacuum, a complete hardness analysis of the coated discs was performed, resulting in values ranging from ~4 to 7 GPa, depending on the grid design. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings)

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