Research

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16 pages, 8455 KiB

Open AccessArticle

Insight into Microstructure Evolution and Corrosion Mechanisms of K₂ZrF₆/Al₂O₃-Doped Hot-Dip Aluminum/Micro-Arc Oxidation Coatings

by Shuliang Wang, Xiaofei Peng, Yi Yang, Shidong Wang, Mingyu Wu, Ping Hu and Chunyan Fu

Coatings 2023, 13(9), 1543; https://doi.org/10.3390/coatings13091543 - 04 Sep 2023

Cited by 1 | Viewed by 940

Abstract

In this study, we investigated the impact of K₂ZrF₆/Al₂O₃ composite additives on the microstructure evolution and corrosion behavior of ceramic coatings formed through micro-arc oxidation (MAO) treatment on hot-dip aluminum-coated 316L stainless steel surfaces. Our findings [...] Read more.

In this study, we investigated the impact of K₂ZrF₆/Al₂O₃ composite additives on the microstructure evolution and corrosion behavior of ceramic coatings formed through micro-arc oxidation (MAO) treatment on hot-dip aluminum-coated 316L stainless steel surfaces. Our findings revealed the successful preparation of micro-arc oxidation ceramic coatings, presenting a dual-layer structure consisting of a porous micro-arc oxidation ceramic outer layer and a relatively dense/thick hot-dip aluminum inner layer. The incorporation of K₂ZrF₆/Al₂O₃ composite additives induced a self-sealing effect on the ceramic coating surface. Optimal coating performance was achieved with a composite additive concentration of 7.5 g/L, resulting in remarkable improvements not only in thickness, hardness, and surface smoothness but also in corrosion resistance. This research introduces a pioneering investigation of K₂ZrF₆/Al₂O₃ composite additives in the context of micro-arc oxidation technology, offering fresh perspectives and methodologies for the development of highly corrosion-resistant materials. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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11 pages, 18606 KiB

Open AccessArticle

Influence of Laser Power on Microstructure and Properties of Al-Si+Y₂O₃ Coating

by Yali Gao, Pengyong Lu, Sicheng Bai, Baolong Qin and Dongdong Zhang

Coatings 2023, 13(7), 1289; https://doi.org/10.3390/coatings13071289 - 23 Jul 2023

Cited by 4 | Viewed by 882

Abstract

Al-Si/7.5 wt.%Y₂O₃ coatings were prepared on Mg alloy with laser cladding to enhance the wear and corrosion resistance of substrate. The influence of laser power on the microstructure and properties of the coating were discussed. The results uncovered that the [...] Read more.

Al-Si/7.5 wt.%Y₂O₃ coatings were prepared on Mg alloy with laser cladding to enhance the wear and corrosion resistance of substrate. The influence of laser power on the microstructure and properties of the coating were discussed. The results uncovered that the coatings consisted primarily of Mg₂Si, Mg₁₇Al₁₂, Mg₂Al₃, Al₄MgY, and α-Mg phases. Through calculation, it was observed that the crystal size decreased with the decrease in the laser power. Y₂O₃ gave the coating a better strengthening effect due to the fine-grain strengthening and hard-phase strengthening. The average hardness of the coating with laser power of 1100 W achieved 312 HV, which was approximately 4.2 times that of the substrate. The wear volume of the coating was 22.2% that of the substrate. Compared with Mg alloy, the self-corrosion potential of the coating increased by 1.09 V, and the self-corrosion current density decreased by three orders of magnitude. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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12 pages, 18818 KiB

Open AccessArticle

Abrasive Wear and Physical Properties of In-Situ Nano-TiC_x Reinforced Cu–Cr–Zr Composites

by Dongdong Zhang, Pengyong Lu, Xiya He and Yali Gao

Coatings 2023, 13(7), 1263; https://doi.org/10.3390/coatings13071263 - 18 Jul 2023

Cited by 2 | Viewed by 835

Abstract

Cu–Cr–Zr alloys reinforced in situ with TiC_x nanoparticles were prepared via combustion synthesis and electromagnetic stirring casting. The microstructure of TiC_x/Cu-Cr-Zr composites with various contents was analyzed. The microhardness and Brinell hardness of the composites were determined; the average volumetric [...] Read more.

Cu–Cr–Zr alloys reinforced in situ with TiC_x nanoparticles were prepared via combustion synthesis and electromagnetic stirring casting. The microstructure of TiC_x/Cu-Cr-Zr composites with various contents was analyzed. The microhardness and Brinell hardness of the composites were determined; the average volumetric abrasive wear rate and worn surface of the composites were investigated; and the electrical, thermal conductivity and thermal expansion coefficients of the materials were discussed. The results indicated that the addition of TiC_x particles transformed the Cu–Cr–Zr matrix alloy microstructure from a dendritic to an equiaxed crystal, and the grain size was significantly refined as the amount added was increased. The composites with high TiCx content possessed higher hardness and abrasive wear resistance. The addition of TiC_x particles reduced the electrical and thermal conductivity and thermal expansion coefficients of the materials. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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10 pages, 5415 KiB

Open AccessArticle

Effect of Powder Recycling on the Organization and Mechanical Properties of GH4169 Alloy by Laser Metal Deposition

by Haibo Zhang, Jieshuai Li and Yingqiu Li

Coatings 2023, 13(3), 659; https://doi.org/10.3390/coatings13030659 - 22 Mar 2023

Cited by 1 | Viewed by 1092

Abstract

The purpose of this research is to prepare GH4 169 alloy specimens by laser metal deposition, by investigating the changes in powder morphology, powder particle size, and elemental content during the cycling process. As well as the pore defects and microstructure of deposited [...] Read more.

The purpose of this research is to prepare GH4 169 alloy specimens by laser metal deposition, by investigating the changes in powder morphology, powder particle size, and elemental content during the cycling process. As well as the pore defects and microstructure of deposited samples prepared from recycled powder, we analyzed the changes in powder properties during the cycling process and the effects of using recycled powder on the organization and properties of LMD-deposited specimens. It was shown that the average particle size of the powder increased with the increase in the size of powder recycling, from 59.861 µm in the original powder to 64.144 µm after four cycles, with the phenomenon of powder burnout and satellite ball. The elemental content of the powder changed with the increase in the number of cycles, among which the elemental content of Nb increased significantly from 4.31 wt% of the original powder to 7.97 wt% after four cycles, the proportion of Laves phase in the deposited samples increased, the porosity and pore size increased, the tensile strength of the specimen decreased from 1046 MPa of the original powder to 936 MPa, the tensile strength decreased by 10.5%, and the elongation was increased to 27% from 11% of the original powder. Powder recycling can lead to powder aging and reduce the mechanical properties of the laser metal deposited formed parts. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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12 pages, 7071 KiB

Open AccessArticle

Investigation of the Microstructure and Wear Properties of Laser Clad Al-Si Coatings Containing Different Y₂O₃ Contents

by Dongdong Zhang, Xiya He, Yali Gao and Baolong Qin

Coatings 2023, 13(2), 308; https://doi.org/10.3390/coatings13020308 - 30 Jan 2023

Cited by 5 | Viewed by 1226

Abstract

Y₂O₃-reinforced Al-Si alloy coatings were prepared on the surface of a Mg alloy by the laser cladding technique. The microstructure, hardness, and wear resistance of the coatings were analyzed using an X-ray diffractometer, a scanning electron microscope, an energy [...] Read more.

Y₂O₃-reinforced Al-Si alloy coatings were prepared on the surface of a Mg alloy by the laser cladding technique. The microstructure, hardness, and wear resistance of the coatings were analyzed using an X-ray diffractometer, a scanning electron microscope, an energy spectrometer, a Vickers hardness tester, and a friction wear tester. The effect of different additions of Y₂O₃ on the microstructure and properties of the coatings was investigated. The results indicate that the addition of Y₂O₃ leads to a significant refinement of the grain size and a denser microstructure of the coatings. Coatings with a high Y₂O₃ content provide superior hardness and wear resistance. With a Y₂O₃ content of 7.5 wt.%, the coating exhibits the finest grain size, highest hardness, and smallest wear volume. Excessive amounts of Y₂O₃, however, cause a reduction in the surface properties of the coating. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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13 pages, 4340 KiB

Open AccessArticle

Study on Anti-Scale and Anti-Corrosion of Polydopamine Coating on Metal Surface

by Xu-Liang Yu, Bing-Bing Wang, Zhi-Ming Xu and Wei-Mon Yan

Coatings 2023, 13(2), 306; https://doi.org/10.3390/coatings13020306 - 29 Jan 2023

Cited by 3 | Viewed by 1834

Abstract

Some surface coatings can protect metal surfaces and reduce scale deposition. Based on that, the biomimetic material polydopamine (PDA) can form a stable coating on many material surfaces; therefore, we propose an efficient one-step electroplating method for preparing anti-scale PDA coatings with high [...] Read more.

Some surface coatings can protect metal surfaces and reduce scale deposition. Based on that, the biomimetic material polydopamine (PDA) can form a stable coating on many material surfaces; therefore, we propose an efficient one-step electroplating method for preparing anti-scale PDA coatings with high stability. The scale deposition test showed that the deposition weight of calcium carbonate on the coating is less than that of carbon steel after immersing in a supersaturated solution of calcium carbonate for 12 h at 70 °C and 90 °C, with a coating scale-inhibition efficiency of 55.02% and 66.96%, respectively. By using molecular dynamics simulation, it was found that water adsorption layers exist near the metal’s surface, and the existence of water adsorption layers on the hydrophilic surface is the main reason for the initial deposition of calcium carbonate. The interaction energy between the PDA molecular layer and water is weaker (−5.69 eV) for the surface with the PDA coating, and there is no dense water adsorption layer on the coating, which leads to the low probability of calcium carbonate adsorption on the PDA coating surface. Therefore, PDA coating can inhibit the deposition of calcium carbonate on the surface. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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25 pages, 7115 KiB

Open AccessArticle

Laser Ablation of Copper Alloy under Varying Environmental Conditions to Achieve Purpose-Built Surface Structures

by Asadullah Dawood, Naveed Ahmed, Shazia Bashir, Asma Hayat, Syed Muhammad Abouzar Sarfraz and Ambreen Ayub

Coatings 2022, 12(12), 1972; https://doi.org/10.3390/coatings12121972 - 15 Dec 2022

Cited by 2 | Viewed by 1661

Abstract

In the manufacturing industry, surface structures and surface topographies present at functional areas of the mechanical parts play a vital role in various performance characteristics, such as corrosion resistance, weldability, and wear behaviors, etc. Copper–zinc alloys are extensively used in the manufacturing industry. [...] Read more.

In the manufacturing industry, surface structures and surface topographies present at functional areas of the mechanical parts play a vital role in various performance characteristics, such as corrosion resistance, weldability, and wear behaviors, etc. Copper–zinc alloys are extensively used in the manufacturing industry. Laser ablation has the potential to create a variety of surface structures on the ablated substrate. The size and geometry of such structures largely depend on the selection of process parameters and the ablation environment. In the present study, a copper–zinc alloy (95% Cu and 5% Zn) has been laser ablated under different gaseous and magnetic environments to realize a variety of micro-structuring at the ablation surfaces. The effect of plasma plume pressure on the geometry of the structures is deeply investigated through optical emission spectroscopy (OES) and scanning electron microscopy (SEM). By analytically evaluating thermal beta (βt), directional beta (βd), and containment radii (Rs) for the plasma of the Cu–Zinc alloy, the validity of magnetic confinement has been proven. In general, five types of microstructures are produced: micro-sized spherical cones, mounted ablated networks, cavities, pores, ridges, and ablation channels with uplifted cones. Moreover, it has been found that, under a magnetic environment, the geometry of the structures is distinct and well-defined compared to those structures achieved when the ablation is carried out without applying a magnetic field. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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15 pages, 22745 KiB

Open AccessArticle

Microstructure and Mechanical Properties of Ni-Based Alloy Composite Coating on Cr12MoV by Laser Cladding

by Yali Gao, Yan Tong, Li Guohui, Pengyong Lu and Dongdong Zhang

Coatings 2022, 12(11), 1632; https://doi.org/10.3390/coatings12111632 - 27 Oct 2022

Cited by 11 | Viewed by 1472

Abstract

Cr12MoV has been widely used in the manufacture of stamping and drawing dies. In the present study, an attempt was made to improve the mechanical properties of Cr12MoV by laser cladding Ni60 alloy reinforced by WC. X-ray diffraction (XRD), scanning electron microscopy (SEM), [...] Read more.

Cr12MoV has been widely used in the manufacture of stamping and drawing dies. In the present study, an attempt was made to improve the mechanical properties of Cr12MoV by laser cladding Ni60 alloy reinforced by WC. X-ray diffraction (XRD), scanning electron microscopy (SEM), a microhardness tester, and a friction and wear test prototype were used to analyze the macroscopic morphology, microstructure, and mechanical properties of the coating. The results showed that the coating mainly was composed of Cr-Fe-Ni, γ-(Fe, Ni), Cr₂₃C₆, Cr₇C₃, and W₂C phases. The cladding layer presented the dendritic eutectic structure enriched Cr, Fe, and Ni. Zigzag-shaped dendrites with thicknesses of 50~80 μm of the bonding zone ensured the strong metallurgical bonding. Due to solid solution strengthening, dispersion hardening, and grain refinement, the hardness of the coating reached 745 HV, which was 3.5 times that of the substrate. The wear volume of the coating was 14 × 10⁻³ mm³, which was 48% lower than that of the substrate (27 × 10⁻³ mm³). The coating had the abrasive wear; however, the substrate had the adhesive wear besides the abrasive wear. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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12 pages, 8720 KiB

Open AccessArticle

Research on Wear and Corrosion Resistance of Ni60-WC Coating Fabricated by Laser on the Preheated Copper Alloy

by Yu Liu, Tianhao Xu and Guohui Li

Coatings 2022, 12(10), 1537; https://doi.org/10.3390/coatings12101537 - 13 Oct 2022

Cited by 5 | Viewed by 1547

Abstract

The copper alloy is widely used to prepare pipes in ocean engineering. The surface is washed and corroded by seawater for a long time, which gradually shortens the service life of the condenser tube. In order to improve the wear and corrosion resistance [...] Read more.

The copper alloy is widely used to prepare pipes in ocean engineering. The surface is washed and corroded by seawater for a long time, which gradually shortens the service life of the condenser tube. In order to improve the wear and corrosion resistance of copper alloy, a Ni60-WC coating was fabricated on a preheated copper alloy by laser cladding. Experiments on the Ni60-WC coatings were carried out by SEM, XRD, Vickers-microhardness meter, wear tester and electrochemical workstation. The microstructure, phases, hardness, wear and corrosion resistance were investigated. The results show that from the top to bottom, the microstructures were columnar dendrites, dendritic crystals and grains, respectively. The wear rate of the Ni60-WC coating was only 4.9 × 10⁻⁵ mm³·N⁻¹·m⁻¹, which was only 1.14% of copper substrate. In addition, the corrosion current density was 2.34 × 10⁻⁷ mA·mm⁻², which was much lower than that of copper alloy substrate (1.14 × 10⁻⁶ mA·mm⁻²). The experimental results show that this Ni60-WC coating has a good metallurgical bonding and hardness, and it also has good wear and corrosion resistance, which is helpful to improve the service life of the condenser tube. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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24 pages, 80652 KiB

Open AccessArticle

Surface Structuring and Thin Film Coating through Additive Concept Using Laser Induced Plasma of Mg Alloy: A Comparison between the Presence and Absence of Transverse Magnetic Field (TMF)

by Asadullah Dawood, Shazia Bashir, Naveed Ahmed, Asma Hayat, Abdullah Yahia AlFaify, Syed Muhammad Abouzar Sarfraz, Shahab Ahmed Abbasi and Ateekh Ur Rehman

Coatings 2022, 12(9), 1316; https://doi.org/10.3390/coatings12091316 - 09 Sep 2022

Cited by 1 | Viewed by 1725

Abstract

In the present study, the influence of a 1.1 tesla Transverse Magnetic Field (TMF) on Laser-Induced Breakdown Spectroscopy (LIBS) of Mg-alloy plasma has been explored. The Mg plasma was produced using an Nd: YAG laser (1064 nm, 10 ns) at an intensity of [...] Read more.

In the present study, the influence of a 1.1 tesla Transverse Magnetic Field (TMF) on Laser-Induced Breakdown Spectroscopy (LIBS) of Mg-alloy plasma has been explored. The Mg plasma was produced using an Nd: YAG laser (1064 nm, 10 ns) at an intensity of 2 GW/cm². Inert gases of Ar, Ne, and He were filled as environmental gases at pressures ranging from 1 to 100 Torr. Optical emission spectra from laser-produced plasma were detected with the help of a spectrometer, and plasma parameters such as excitation temperature (T_exc) and electron number density (n_e) were evaluated. Enhancement in the Mg plasma’s T_exc and n_e in the presence of TMF was noticed under all experimental conditions, including different ambient gases with varying pressures and time delays (0.42 µs–9.58 µs). Plasma confinement by applied TMF was analytically evaluated through thermal beta (β_t) values, which were <1 under all circumstances. The highest T_exc and n_e values (17,259 K and 11.5 × 10¹⁷ cm⁻³) for Mg-alloy plasma were obtained with ambient Ar in TMF, while the lowest values (8793 K and 1.0 × 10¹⁷ cm⁻³) were obtained in presence of He gas in the absence of TMF. SEM analysis was used to determine the surface structure of laser-ablated Mg alloy in the presence and absence of TMF. It revealed that the formation of cones, cavities, and non-uniform melting are characteristic features of ambient Ar, while spikes and cavities are prominent features in Ne gas environments. Conical spikes and dendrites are distinct features when ambient He is present. In comparison with the field-free condition, distinct and well-defined structures were observed in the presence of TMF. By controlling LPP parameters, the surface structuring of Mg alloy can be controlled. The optimization and enhancement of LPP parameters make it a highly useful tool for thin film deposition, coatings of multilayers, and ion implantation/doping. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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Review

Jump to: Research

11 pages, 12070 KiB

Open AccessReview

Investigation of the Change in Roughness and Microhardness during Laser Surface Texturing of Copper Samples by Changing the Process Parameters

by Risham Singh Ghalot, Lyubomir Lazov, Emil Yankov and Nikolay Angelov

Coatings 2023, 13(11), 1970; https://doi.org/10.3390/coatings13111970 - 20 Nov 2023

Cited by 1 | Viewed by 717

Abstract

The aim of this research is to achieve a high-quality and long-lasting laser marking of ammunition, which is of interest to the defense industry. The study is about the effects of speed, raster pitch and power on the roughness and microhardness of the [...] Read more.

The aim of this research is to achieve a high-quality and long-lasting laser marking of ammunition, which is of interest to the defense industry. The study is about the effects of speed, raster pitch and power on the roughness and microhardness of the marked areas of copper samples. The experiments were carried out with a fiber laser and a copper bromide laser—modern lasers widely used in industrial production. Laser power, scan speed and raster step were varied to determine their effects on the resulting microhardness and surface roughness. The lasers operate in different wavelength ranges, with the optical laser operating at 1064 nm in the near-infrared region and the copper bromide laser at 511 nm and 578 nm in the visible region, allowing the influence of wavelengths on the process to be investigated. The roughness and microhardness velocity dependence for three powers and two pulse durations for the fiber laser were obtained from the experimental data. The dependence of roughness and microhardness on the raster step for both types of lasers was also demonstrated. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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