Research

15 pages, 24803 KiB

Open AccessArticle

Quality of Zinc Coating Formed on Structural Steel by Hot-Dip Galvanizing after Surface Contamination

by Jiřina Vontorová, Petr Mohyla and Kateřina Kreislová

Coatings 2024, 14(4), 493; https://doi.org/10.3390/coatings14040493 - 17 Apr 2024

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This paper deals with the evaluation of the surface of structural steel whose samples were deliberately contaminated with transparent spray primer, adhesive label glue, and welding sprays prior to hot-dip galvanizing. The galvanized samples were studied by optical microscopy, GDOES, adhesion tests, and [...] Read more.

This paper deals with the evaluation of the surface of structural steel whose samples were deliberately contaminated with transparent spray primer, adhesive label glue, and welding sprays prior to hot-dip galvanizing. The galvanized samples were studied by optical microscopy, GDOES, adhesion tests, and condensation humidity tests. The effect of surface contamination on the quality of the zinc coating was found to be significant. In some cases, the zinc coating is damaged (after contamination with welding sprays), in others, it is completely absent (after contamination with spray primer or adhesive label glue). Full article

(This article belongs to the Special Issue Modern Methods of Shaping the Structure and Properties of Coatings)

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13 pages, 6534 KiB

Open AccessArticle

Simulation of TiN/Ti Multilayer Coating under the Impact of Multiple Particles Based on Cohesive Element

by Zhanwei Yuan, Wenlong Shi, Guangyu He, Yan Chai, Zhufang Yang and Min Guo

Coatings 2024, 14(4), 470; https://doi.org/10.3390/coatings14040470 - 12 Apr 2024

Viewed by 353

Abstract

In order to investigate the damage behavior of TiN/Ti multilayer coating under multi-particle impact and the influence of impact angle on erosion resistance, the ABAQUS 2019 software and the cohesive element technology were used for simulation. The results showed that, during the impact [...] Read more.

In order to investigate the damage behavior of TiN/Ti multilayer coating under multi-particle impact and the influence of impact angle on erosion resistance, the ABAQUS 2019 software and the cohesive element technology were used for simulation. The results showed that, during the impact process, the upper surface of the TiN layer that was directly below the impact center was mainly subjected to compressive stress, while the lower surface was subjected to tensile stress. At the impact contact edge, tensile stress appeared on the upper surface of the TiN layer, while compressive stress appeared on the lower surface. The increase in the number of impacts leads to an increase in the maximum S11 stress inside the coating and the maximum displacement of the impact center during the impact process. The plastic damage was greater at the locations with higher strain in the Ti sublayer. During the impact process, severe damage occurred in both the top TiN layer and interface areas, and material failure occurred in the impact area. The increase in impact angle leads to an increase in the plastic strain energy of the entire model after the impact and the maximum S11 stress inside the coating during the impact process. Full article

(This article belongs to the Special Issue Modern Methods of Shaping the Structure and Properties of Coatings)

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18 pages, 6548 KiB

Open AccessArticle

Dual Microcapsules Encapsulating Liquid Diamine and Isocyanate for Application in Self-Healing Coatings

by Huaixuan Mu, Yiqing Deng, Wangcai Zou, Xiandi Yang and Qiang Zhao

Coatings 2024, 14(4), 410; https://doi.org/10.3390/coatings14040410 - 29 Mar 2024

Viewed by 479

Abstract

Dual microcapsule systems, especially those based on the polyurea matrix, have emerged as pivotal components driving innovation in self-healing materials, thanks to the intrinsic properties of polyurea, primarily diamine and diisocyanate, rendering it an optimal choice for enhancing self-healing coatings. However, the encapsulation [...] Read more.

Dual microcapsule systems, especially those based on the polyurea matrix, have emerged as pivotal components driving innovation in self-healing materials, thanks to the intrinsic properties of polyurea, primarily diamine and diisocyanate, rendering it an optimal choice for enhancing self-healing coatings. However, the encapsulation of polyurea components is fraught with substantial technical hurdles. Addressing these challenges, a novel methodology has been devised, leveraging n-heptane as a solvent in the liquid diamine emulsion process to facilitate the synthesis of diamine microcapsules. These microcapsules exhibit a uniform spherical morphology and a robust shell structure, with an encapsulated core material ratio reaching 39.69%. Analogously, the encapsulation process for diisocyanate has been refined, achieving a core material percentage of 10.05 wt. %. The integration of this bifunctional microcapsule system into diverse polymeric matrices, including epoxy resins and polyurethanes, has been demonstrated to significantly enhance the self-healing efficacy of the resultant coatings. Empirical validation through a series of tests, encompassing scratch, abrasion, and saltwater immersion assays, has revealed self-healing efficiencies of 21.8% and 33.3%, respectively. These results indicate significant improvements in the durability and self-repair capability of coatings, marking a notable advancement in self-healing materials with promising potential for tailored applications in automotive, aerospace, and construction industries. Full article

(This article belongs to the Special Issue Modern Methods of Shaping the Structure and Properties of Coatings)

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24 pages, 8097 KiB

Open AccessArticle

CoCrFeMnNi_0.8V/Cr₃C₂-Ni₂₀Cr High-Entropy Alloy Composite Thermal Spray Coating: Comparison with Monolithic CoCrFeMnNi_0.8V and Cr₃C₂-Ni₂₀Cr Coatings

by Stavros Kiape, Maria Glava, Emmanuel Georgatis, Spyros Kamnis, Theodore E. Matikas and Alexandros E. Karantzalis

Coatings 2024, 14(4), 402; https://doi.org/10.3390/coatings14040402 - 28 Mar 2024

Viewed by 714

Abstract

High-entropy alloys (HEAs) are revolutionizing the field of surface engineering, challenging traditional alloy frameworks with their superior mechanical attributes and resistance to corrosion. This investigation delves into the properties of the CoCrFeMnNi_0.8V HEAs, both as a standalone material and when blended [...] Read more.

High-entropy alloys (HEAs) are revolutionizing the field of surface engineering, challenging traditional alloy frameworks with their superior mechanical attributes and resistance to corrosion. This investigation delves into the properties of the CoCrFeMnNi_0.8V HEAs, both as a standalone material and when blended with Cr₃C₂-Ni₂₀Cr, to evaluate their efficacy as cutting-edge surface treatments. The addition of vanadium to the CoCrFeMnNi_0.8V alloy results in a distinctive microstructure that improves hardness and resistance to abrasion. The incorporation of Cr₃C₂-Ni₂₀Cr particles enhances the alloy’s toughness and longevity. Employing high-velocity oxy-fuel (HVOF) thermal spray methods, these coatings are deposited onto steel substrates and undergo detailed evaluations of their microstructural characteristics, abrasion, and corrosion resistance. Findings reveal the CoCrFeMnNi_0.8V coating’s exceptional ability to withstand corrosion, especially in environments rich in chlorides. The hybrid coating benefits from the combination of the HEA’s inherent corrosion resistance and the enhanced wear and corrosion resistance provided by Cr₃C₂-Ni₂₀Cr, delivering comprehensive performance for high-stress applications. Through the fine-tuning of the application process, the Cr₃C₂-Ni₂₀Cr reinforced high-entropy alloy coating emerges as a significant advancement in protective surface technology, particularly for use in marine and corrosive settings. This study not only highlights the adaptability of HEAs in surface engineering but also prompts further investigation into innovative material pairings. Full article

(This article belongs to the Special Issue Modern Methods of Shaping the Structure and Properties of Coatings)

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13 pages, 101040 KiB

Open AccessArticle

Effect of the Shielding Gas and Heat Treatment in Inconel 625 Coatings Deposited by GMAW Process

by Eliane Alves Kihara, Henara Lillian Costa and Demostenes Ferreira Filho

Coatings 2024, 14(4), 396; https://doi.org/10.3390/coatings14040396 - 28 Mar 2024

Viewed by 665

Abstract

Friction, wear, and corrosion of engineering components operating in harsh environments can be substantially improved by applying hard, corrosion-resistant coatings to prolong their useful lives. Nickel superalloys are particularly relevant due to their excellent mechanical properties and corrosion resistance at elevated temperatures. Among [...] Read more.

Friction, wear, and corrosion of engineering components operating in harsh environments can be substantially improved by applying hard, corrosion-resistant coatings to prolong their useful lives. Nickel superalloys are particularly relevant due to their excellent mechanical properties and corrosion resistance at elevated temperatures. Among the various coating techniques, arc welding processes are suitable due to their good deposition rate and reliability. This work aimed to evaluate the effect of the shielding gas and after-deposition heat treatment on the microstructure and mechanical properties of Inconel 625 coatings deposited by the GMAW process. The coatings were deposited onto carbon steel plates using two mixtures of shielding gases (Ar+25%CO₂ and Ar+25%He) without interpass temperature control. The specimens were analyzed both as welded and after heat treatment (heating for 1 h at 1000 °C and air cooling) using Vickers hardness tests, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and wavelength dispersion spectrometry (WDS). The coatings that used Ar+25%He-shielding gas were harder and showed more precipitate formation, which was associated with the higher cooling rates involved. As for the heat treatment, it led to a reduction in the segregation of the alloying elements in the interdendritic region via diffusion and a reduction in surface hardness. Full article

(This article belongs to the Special Issue Modern Methods of Shaping the Structure and Properties of Coatings)

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16 pages, 4089 KiB

Open AccessArticle

Effect of Ultrasonic Vibration on Microstructure and Antifouling Capability of Cu-Modified TiO₂ Coating Produced by Micro-Arc Oxidation

by Pengfei Hu, Liyang Zhu, Jiejun Liu, You Lv, Guangyi Cai and Xinxin Zhang

Coatings 2024, 14(4), 376; https://doi.org/10.3390/coatings14040376 - 22 Mar 2024

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Abstract

Ti and its alloys have received wide attention in marine engineering. However, the limited anti-biofouling capability may hinder their wide application. In the present work, micro-arc oxidation (MAO) with and without the introduction of ultrasonic vibration (UV) has been conducted on metallic Ti [...] Read more.

Ti and its alloys have received wide attention in marine engineering. However, the limited anti-biofouling capability may hinder their wide application. In the present work, micro-arc oxidation (MAO) with and without the introduction of ultrasonic vibration (UV) has been conducted on metallic Ti substrate in an aqueous solution containing Na₂Cu-EDTA to produce a Cu-modified TiO₂ coating. Microstructural characterization reveals that the introduction of UV increased the thickness of the coating (ranging from ~13.5 μm to ~26.2 μm) compared to the coating (ranging from ~8.1 μm to ~12.8 μm) without UV. A relatively higher Cu content (~2.13 wt.%) of the coating with UV relative to the coating (~1.39 wt.%) without UV indicates that UV enhances the incorporation of Cu into TiO₂. Further, both electrochemical properties and the response to sulfate-reducing bacteria (SRB) were evaluated, revealing that UV introduction endows Cu-modified TiO₂ coating with enhanced corrosion resistance and antifouling capability. The present results suggest that ultrasound-auxiliary micro-arc oxidation (UMAO) obviously enhances the surface performance of Ti alloys for promising applications in marine engineering. Full article

(This article belongs to the Special Issue Modern Methods of Shaping the Structure and Properties of Coatings)

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22 pages, 11896 KiB

Open AccessArticle

Study on the Self-Repairing Effect of Nanoclay in Powder Coatings for Corrosion Protection

by Marshall Shuai Yang, Jinbao Huang, Hui Zhang, James Joseph Noël, Yolanda Susanne Hedberg, Jian Chen, Ubong Eduok, Ivan Barker, Jeffrey Daniel Henderson, Chengqian Xian, Haiping Zhang and Jesse Zhu

Coatings 2023, 13(7), 1220; https://doi.org/10.3390/coatings13071220 - 07 Jul 2023

Cited by 1 | Viewed by 1646

Abstract

Powder coatings are a promising, solvent-free alternative to traditional liquid coatings due to the superior corrosion protection they provide. This study investigates the effects of incorporating montmorillonite-based nanoclay additives with different particle sizes into polyester/triglycidyl isocyanurate (polyester/TGIC) powder coatings. The objective is to [...] Read more.

Powder coatings are a promising, solvent-free alternative to traditional liquid coatings due to the superior corrosion protection they provide. This study investigates the effects of incorporating montmorillonite-based nanoclay additives with different particle sizes into polyester/triglycidyl isocyanurate (polyester/TGIC) powder coatings. The objective is to enhance the corrosion-protective function of the coatings while addressing the limitations of commonly employed epoxy-based coating systems that exhibit inferior UV resistance. The anti-corrosive and surface qualities of the coatings were evaluated via neutral salt spray tests, electrochemical measurements, and surface analytical techniques. Results show that the nanoclay with a larger particle size of 18.38 µm (D₅₀, V) exhibits a better barrier effect at a lower dosage of 4%, while a high dosage leads to severe defects in the coating film. Interestingly, the coating capacitance is found, via electrochemical impedance spectroscopy, to decrease during the immersion test, indicating a self-repairing capability of the nanoclay, arising from its swelling and expansion. Neutral salt spray tests suggest an optimal nanoclay dosage of 2%, with the smaller particle size (8.64 µm, D₅₀, V) nanoclay providing protection for 1.5 times as many salt spray hours as the nanoclay with a larger particle size. Overall, incorporating montmorillonite-based nanoclay additives is suggested to be a cost-effective approach for significantly enhancing the anti-corrosive function of powder coatings, expanding their application to outdoor environments. Full article

(This article belongs to the Special Issue Modern Methods of Shaping the Structure and Properties of Coatings)

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16 pages, 10483 KiB

Open AccessArticle

Microstructural Evaluation of Thermal-Sprayed CoCrFeMnNi_0.8V High-Entropy Alloy Coatings

by Athanasios K. Sfikas, Spyros Kamnis, Martin C. H. Tse, Katerina A. Christofidou, Sergio Gonzalez, Alexandros E. Karantzalis and Emmanuel Georgatis

Coatings 2023, 13(6), 1004; https://doi.org/10.3390/coatings13061004 - 28 May 2023

Cited by 4 | Viewed by 1716

Abstract

The aim of this work is to improve the understanding of the effect of the cooling rate on the microstructure of high-entropy alloys, with a focus on high-entropy alloy coatings, by using a combined computational and experimental validation approach. CoCrFeMnNi_0.8V coatings [...] Read more.

The aim of this work is to improve the understanding of the effect of the cooling rate on the microstructure of high-entropy alloys, with a focus on high-entropy alloy coatings, by using a combined computational and experimental validation approach. CoCrFeMnNi_0.8V coatings were deposited on a steel substrate with high velocity oxy-air-fuel spray with the employment of three different deposition temperatures. The microstructures of the coatings were studied and compared with the microstructure of the equivalent bulk high-entropy alloy fabricated by suction casting and powder fabricated by gas atomization. According to the results, the powder and the coatings deposited by low and medium temperatures consisted of a BCC microstructure. On the other hand, the microstructure of the coating deposited by high temperature was more complex, consisting of different phases, including BCC, FCC and oxides. The phase constitution of the bulk high-entropy alloy included an FCC phase and sigma. This variation in the microstructural outcome was assessed in terms of solidification rate, and the results were compared with Thermo-Calc modelling. The microstructure can be tuned by the employment of rapid solidification techniques such as gas atomization, as well as subsequent processing such as high velocity oxy-air-fuel spray with the use of different spray parameters, leading to a variety of microstructural outcomes. This approach is of high interest for the field of high-entropy alloy coatings. Full article

(This article belongs to the Special Issue Modern Methods of Shaping the Structure and Properties of Coatings)

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