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15 pages, 4014 KiB

Open AccessArticle

Study on the Embrittlement of Steel Grain Boundaries Caused by Penetration and Diffusion of Liquid Copper

by Yu Chu, Donghui Wen, Wei Wang, Changzhi Fan and Kun Chen

Coatings 2025, 15(4), 408; https://doi.org/10.3390/coatings15040408 - 29 Mar 2025

Viewed by 259

Abstract

This paper investigated and experimentally analyzed the penetration behavior of liquid copper along austenite grain boundaries (GBs) at high temperatures. The microstructure of the liquid copper channel network along GBs and triple junctions (TJs), as well as the TJ wetting, was observed and [...] Read more.

This paper investigated and experimentally analyzed the penetration behavior of liquid copper along austenite grain boundaries (GBs) at high temperatures. The microstructure of the liquid copper channel network along GBs and triple junctions (TJs), as well as the TJ wetting, was observed and interpreted through diffusion-controlled premelted GB formation. The concentration distribution results along GBs show that copper diffusion in both the near-surface premelted GBs and the non-surface-layer solid-state GBs conform to the diffusion equation, though the diffusion coefficients differ by approximately one order of magnitude. However, the copper concentration at premelted GBs cannot be fully described by an error solution. Using a modified diffusion equation when considering the concentration dependence of the GB diffusion coefficient provides a more accurate description, aligning better with experimental characteristics. Electron backscatter diffraction measurements indicate that the copper orientation at premelted GBs remains consistent with that of surface copper coating, whereas that at solid-state GBs undergoes significant changes. This finding is consistent with the argument that the corresponding material states at premelted GBs are different from those at solid-state GBs, thus providing experimental evidence for the diffusion equation solutions presented above. It provides a theoretical reference for understanding and preventing liquid metal embrittlement. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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13 pages, 7264 KiB

Open AccessArticle

Friction Behavior of Molybdenum Disulfide/Polytetrafluoroethylene-Coated Cemented Carbide Fabricated with a Spray Technique in Dry Friction Conditions

by Li Zhang and Wenlong Song

Coatings 2025, 15(3), 324; https://doi.org/10.3390/coatings15030324 - 11 Mar 2025

Viewed by 475

Abstract

Cemented carbide has a relatively high surface friction coefficient, which can result in increased wear and energy consumption during friction, ultimately impacting service life and efficiency. In order to improve the tribological properties of the traditionally cemented carbide, the MoS₂ and PTFE [...] Read more.

Cemented carbide has a relatively high surface friction coefficient, which can result in increased wear and energy consumption during friction, ultimately impacting service life and efficiency. In order to improve the tribological properties of the traditionally cemented carbide, the MoS₂ and PTFE (25 wt.%) mixed powders, which were blended with Polyamide-imide (PAI) as the adhesive, were sprayed on the carbide surface at 70 °C. Tests were used to measure the performance of MoS₂/PTFE-coated carbide, such as surface micrographs and cross-section micrographs, surface roughness, adhesion strength between coatings and substrate, and surface microhardness. Sliding friction tests were performed to investigate the friction performance. The test results showed that the adhesion strength between the coatings and substrate was up to 36 N, the hardness was about 0.42 GPa, and the friction coefficient was reduced by about 70%. The lower shear strength of MoS₂/PTFE coatings led to the reduction of friction and wear. The main wear mechanisms of MoS₂/PTFE coatings were surface abrasion and coating flaking. The MoS₂/PTFE coatings present a promising approach to enhance the friction performance of traditional cemented carbide. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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15 pages, 14089 KiB

Open AccessArticle

The Effect of Warm Shot Peening on Microstructure Evolution and Residual Stress in Gradient Nanostructured Mg-8Gd-3Y-0.4Zr Alloys

by Huabing Liu, Xiang Zhang, Xiaoxiao Wei, Jin Gan and Chuanhai Jiang

Coatings 2025, 15(3), 316; https://doi.org/10.3390/coatings15030316 - 9 Mar 2025

Viewed by 575

Abstract

This work systematically investigated the effects of warm shot peening (WSP) on the microstructure evolution, residual stress, and microhardness of the Mg-8Gd-3Y-0.4Zr (GW83) alloy by X-ray diffraction line profile analysis, transmission electron microscopy, and X-ray stress analyzer and hardness tester. The results indicated [...] Read more.

This work systematically investigated the effects of warm shot peening (WSP) on the microstructure evolution, residual stress, and microhardness of the Mg-8Gd-3Y-0.4Zr (GW83) alloy by X-ray diffraction line profile analysis, transmission electron microscopy, and X-ray stress analyzer and hardness tester. The results indicated that severe plastic deformation induced by WSP resulted in a gradient nanostructure in the GW83 alloy, accompanied by significant compressive residual stress. In contrast to conventional SP, WSP led to working softening due to the dynamic recrystallization behavior. The formation of nanograins in the GW83 alloy during WSP occurs in three steps: (i) at an early stage, the introduction of a high density of dislocations and a few deformation twins subdivide bulk grains into substructures; (ii) through the processes of dislocation gliding, accumulation, and rearrangement, these substructures undergo further refinement, gradually evolving into ultrafine grains; and (iii) the inhomogeneous ultrafine grains develop into nanograins through dislocation-assisted lattice rotation and dynamic recrystallization. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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14 pages, 13089 KiB

Open AccessArticle

Atom-Probe Tomographic Characterization of Nanoscale Precipitates in Copper-Bearing Ultra-Low-Carbon High-Strength Steel Tempered at Different Temperatures

by Fengrui Liang, Hang Su, Xiaobing Luo, Zemin Wang, Feng Chai and Yuanyuan Xu

Coatings 2025, 15(2), 208; https://doi.org/10.3390/coatings15020208 - 9 Feb 2025

Viewed by 642

Abstract

Ultra-low-carbon, high-strength steels have gained significant attention due to their exceptional mechanical properties. To enhance the performance of the steel, understanding the precipitation behavior of strengthening precipitates is crucial. In this study, the precipitation behavior of ultra-low-carbon high-strength steel strengthened by nanoscale copper [...] Read more.

Ultra-low-carbon, high-strength steels have gained significant attention due to their exceptional mechanical properties. To enhance the performance of the steel, understanding the precipitation behavior of strengthening precipitates is crucial. In this study, the precipitation behavior of ultra-low-carbon high-strength steel strengthened by nanoscale copper (Cu)-rich precipitates (CRPs) and carbonitride (CN) atomic clusters was characterized using atom-probe tomography after tempering at 400, 450, 600, and 650 °C for 2 h. The results revealed that the nanoscale copper CRPs and the CN atomic clusters were the main strengthening precipitates. The CRPs, enriched only in Cu, were observed at 400 °C. Segregation of nickel (Ni) and manganese (Mn) to the CRPs occurred at 450 °C, and the number densities of CRPs achieved the maximum value, leading to the highest strengthening effects. The size of the CRPs increased with increasing temperature; however, the size of the clusters of the carbide-forming atoms remained at almost ~1.6 nm. At 650 °C, the concentration of Cu, Ni, and Mn atoms in the CRPs was about 85.4, 4.5, and 4 at.%, respectively; however, that of Fe decreased significantly. In the lath boundaries, the size of 10% C and 0.4% C iso-surfaces was relatively larger than that in the matrix. In a reverted austenite region at 600 °C, the concentration of Ni in the reverted austenite, CRPs, and matrix was about 15, 2.5, and 2.5 at.%, respectively. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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13 pages, 4814 KiB

Open AccessArticle

Effects of Annealing Time on the Structure Characteristics and Magnetic Properties of FeSiBPCCuNb Amorphous Ribbons

by Xi Huang, Lianbo Wang, Song Ding, Jiajun Li, Zemin Wang, Min Liu, Zhanyong Wang and Wenlong Zhu

Coatings 2025, 15(1), 50; https://doi.org/10.3390/coatings15010050 - 5 Jan 2025

Viewed by 744

Abstract

In this paper, the structure characteristics and magnetic properties of Fe₈₃Si₆B₆P_1.5C_1.5Cu₁Nb₁ amorphous alloy ribbons annealed at 550 °C for different times were systematically investigated using X-ray diffraction, vibrating sample magnetometer, [...] Read more.

In this paper, the structure characteristics and magnetic properties of Fe₈₃Si₆B₆P_1.5C_1.5Cu₁Nb₁ amorphous alloy ribbons annealed at 550 °C for different times were systematically investigated using X-ray diffraction, vibrating sample magnetometer, and atom probe chromatography. The results show that high-density Cu atomic clusters of appropriate sizes help to stabilize the α-Fe(Si) phase and improve the uniformity of the grains to enhance the soft magnetic properties. The solubility difference between the α-Fe(Si) phase and the B-rich phase, the formation of a localized amorphous structure in the transition region, and the inhibition of nanograin growth. However, when the annealing time is extended, the size of the α-Fe(Si) grains decreases, the grain boundary density increases and secondary phases such as Cu clusters become pinning sites for magnetic domain walls. This leads to a decrease in soft magnetic properties, an increase in hard magnetic properties, and a rapid increase in coercivity. When annealed at 550 °C for 20 min, the number density of Cu atomic clusters was 9.18 × 10²² m⁻³, the spherical equivalent radius was 1.13 ± 0.29 nm, and the ribbons had good soft magnetic properties with a coercivity of 4.59 Oe. The saturation magnetic induction reached a peak value of 185.11 emu/g. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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11 pages, 9742 KiB

Open AccessArticle

Aluminum-Modified Plasma Nitriding with High Efficiency and Enhanced Performance

by Ze He, Wei Wei, Jing Hu and Jingyi Gu

Coatings 2024, 14(11), 1373; https://doi.org/10.3390/coatings14111373 - 29 Oct 2024

Viewed by 981

Abstract

Aluminum-modified plasma nitriding was developed in this research by the addition of a few FeAl particles around samples of 42CrMo middle carbon alloy steel during plasma nitriding. The goal of this study was to enhance nitriding efficiency and the combined performance of the [...] Read more.

Aluminum-modified plasma nitriding was developed in this research by the addition of a few FeAl particles around samples of 42CrMo middle carbon alloy steel during plasma nitriding. The goal of this study was to enhance nitriding efficiency and the combined performance of the steel. The research results show that nitriding efficiency was greatly enhanced, by about 6 times, with the effective hardening layer rising from 224 μm to 1246 μm compared with traditional plasma nitriding at 520 °C/4 h. More importantly, the compound layer increased just a little bit, from 11.64 μm to 14.32 μm, which remarkably reduced the ratio of the compound layer’s thickness to the effective hardening layer’s thickness, thus being quite beneficial to decreasing the brittleness level, making the brittleness level decrease from Level 4 to Level 1. Also, extremely high surface hardness and excellent wear resistance were obtained by aluminum-modified plasma nitriding due to the formation of hard phases of AlN and FeAl in the nitrided layer, with the surface hardness rising from 755 HV_0.025 to 1251 HV_0.025 and the wear rate reducing from 8.15 × 10⁻⁵ g·N⁻¹·m⁻¹ to 4.07 × 10⁻⁵ g·N⁻¹·m⁻¹. In other words, compared with traditional plasma nitriding, wear resistance was enhanced by two times after aluminum-modified plasma nitriding. Therefore, this study can provide comprehensive insights into the surface characteristics and combined performance of aluminum-modified plasma nitriding layers. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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12 pages, 5586 KiB

Open AccessArticle

Study on Characterization of Phase Transition in Continuous Cooling of Carbon Steel Using In Situ Thermovoltage Measurement

by Qihui Wang, Kun Chen, Kejia Liu, Lianbo Wang, Yu Chu and Bichen Xie

Coatings 2024, 14(8), 980; https://doi.org/10.3390/coatings14080980 - 3 Aug 2024

Viewed by 1111

Abstract

In this paper, a self-designed and enhanced thermovoltage measuring device was built to capture thermovoltage curves of 45 steel during continuous cooling. The phase zones of the thermovoltage curve were interpreted based on the Engel–Brewer electron theory and Fe-Fe₃C phase diagram. [...] Read more.

In this paper, a self-designed and enhanced thermovoltage measuring device was built to capture thermovoltage curves of 45 steel during continuous cooling. The phase zones of the thermovoltage curve were interpreted based on the Engel–Brewer electron theory and Fe-Fe₃C phase diagram. The results show that the curve was stratified into three homogeneous phase zones and two-phase transition zones as follows: Zone Ι: single-phase austenite (A) zone; Zone III: austenite and ferrite (A+F) homogeneous phase zone; Zone V: ferrite and pearlite (P+F) homogeneous phase zone; Zone II: austenite to ferrite (A-F) phase transition zone; and Zone IV: austenite to pearlite (A-P) phase transition zone. Notably, the deflection point marked the transition temperature, which indicates that the thermovoltage curve can quantitatively characterize phase formation and transformation, as well as the phase transformation process. Furthermore, the sample was quenched at the measured ferrite phase transition temperature. Microstructure observations, electron probe microanalyzer (EPMA) and microhardness measurements corroborated our findings. Specifically, our experiments reveal ferrite precipitation first from the cold end at the phase transition temperature, leading to increased carbon content in adjacent austenite. The results of this study achieved the in situ characterization of bulk transformations during the materials heat treatment process, which expands the author’s research work conducted previously. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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11 pages, 4624 KiB

Open AccessArticle

Study on High-Temperature, Ultra-Low Wear Behaviors of Ti6Al4V Alloy with Thermal Oxidation Treatment

by Qunfeng Zeng, Shichuan Sun, Zeming Pang and Xunkai Wei

Coatings 2024, 14(4), 416; https://doi.org/10.3390/coatings14040416 - 31 Mar 2024

Cited by 2 | Viewed by 1678

Abstract

Thermal oxidation (TO) is a simple and economical way to enhance the wear resistance of the Ti6Al4V alloy. The TO temperature has a very important effect on the tribological properties of the TiO₂ layer formed. However, the impact of the oxidation temperature [...] Read more.

Thermal oxidation (TO) is a simple and economical way to enhance the wear resistance of the Ti6Al4V alloy. The TO temperature has a very important effect on the tribological properties of the TiO₂ layer formed. However, the impact of the oxidation temperature on the high-temperature tribological behavior of a TO-treated Ti6Al4V alloy is not clear. Therefore, the Ti6Al4V alloy was oxidized at 400 °C, 600 °C, and 700 °C for 36 h, and the sliding friction experiments were conducted at room temperature (RT) and 400 °C with a Si₃N₄ ball as the counter body to comparatively study the effect of the oxidation temperature on the high-temperature friction behavior of the TO-treated Ti6Al4V alloy. The results show that the TO treatment can effectively improve the wear resistance of the samples at both room and high temperatures. Among them, the oxidation-treated samples at 700 °C show the best wear resistance, with a reduction of 92.6% at high temperatures; the amount of wear loss at room temperature was so small that it was almost incalculable. At room temperature, the friction surface formed uneven agglomerate formations, resulting in an elevated coefficient of friction (CoF) compared to the untreated samples. At a high temperature, however, the CoF is reduced compared to the untreated samples due to the formation of a homogeneous transfer film in the wear area that is caused by the interaction of Si₃N₄ and oxygen. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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14 pages, 4306 KiB

Open AccessArticle

Corrosion Performance of Epoxy/Sulfur–Selenium Coating on Q235 Steel

by Konglan Meng, Wei Wei, Kunxia Wei, Igor V. Alexandrov, Xulong An, Dandan Wang and Xiangkui Liu

Coatings 2024, 14(3), 245; https://doi.org/10.3390/coatings14030245 - 20 Feb 2024

Cited by 2 | Viewed by 1607

Abstract

Sulfur powder (99.99%) and selenium powder (99.99%) were mixed and heated to approximately 300 °C to obtain an S-Se alloy. It has good flowability at 130 °C and can be applied to Q235 steel to obtain a S-Se coating. Epoxy was used as [...] Read more.

Sulfur powder (99.99%) and selenium powder (99.99%) were mixed and heated to approximately 300 °C to obtain an S-Se alloy. It has good flowability at 130 °C and can be applied to Q235 steel to obtain a S-Se coating. Epoxy was used as a filler, and the S-Se alloy was applied as a coating. This combination was utilized to create the composite coatings of epoxy/sulfur–selenium (E/S-Se). To investigate the corrosion resistance of this coating on Q235 steel substrate, we conducted measurements and obtained electrochemical impedance spectra (EIS) and linear polarization curves (LPC). These measurements were performed in a three-electrode cell within an electrochemical workstation using a 3.5 wt.% NaCl aqueous solution. By comparing bare Q235 steel, S-Se, and E/S-Se, the study found that the E/S-Se coating had a higher self-corrosion potential (−0.484 V vs. SCE) and the lowest self-corrosion current density (2.361 × 10⁻¹¹ A/cm²). The purpose was to simulate the corrosive environment experienced by condensate return pipe walls in petroleum refining equipment. Additionally, experiments were carried out using 0.01 mol/L HCl solution as the corrosion medium at different temperatures (40 °C, 60 °C, 80 °C). The results indicated that the E/S-Se coating exhibited a lower corrosion rate compared to the Q235 steel substrate. Under immersion conditions at 40 °C and 60 °C, no corrosive substances were detected on the surface of the coating. The test results demonstrated that the E/S-Se coating exhibited superior corrosion resistance compared to the Q235 substrate, providing up to 99% protection for the substrate. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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10 pages, 3791 KiB

Open AccessArticle

Novel Effect of Post-Oxidation on the Comprehensive Performance of Plasma Nitriding Layer

by Jia Ni, Heng Ma, Wei Wei, Xulong An, Minhua Yu and Jing Hu

Coatings 2024, 14(1), 86; https://doi.org/10.3390/coatings14010086 - 8 Jan 2024

Cited by 8 | Viewed by 2004

Abstract

In order to enhance the comprehensive performance of plasma nitrided heavy load components used in corrosive environments, post-oxidation was conducted under different conditions after plasma nitriding 42CrMo4 steel at 500 °C for 5 h. The results show that an oxide film composed of [...] Read more.

In order to enhance the comprehensive performance of plasma nitrided heavy load components used in corrosive environments, post-oxidation was conducted under different conditions after plasma nitriding 42CrMo4 steel at 500 °C for 5 h. The results show that an oxide film composed of Fe₃O₄ and Fe₂O₃ was formed above the compound layer, resulting in a significant increase in corrosion resistance; the self-corrosion potential was greatly increased from −658.72 mV to −429.23 mV. Meanwhile, it needs to be emphasized that the characteristics of the plasma nitriding layer could be effectively adjusted as expected by post-oxidation. The compound layer thickness decreased from 9.41 μm to 3.62 μm by post-oxidation at 400 °C for 2 h, while the thickness of the effective hardening layer increased from 300 μm to 378 μm. Due to the expected change in the characteristics of the plasma nitriding layer, post-oxidation could simultaneously improve the toughness, hardness, and wear resistance of the samples; the brittleness level decreased from Grade 4 to Grade 1; the surface hardness increased from 765 HV_0.05 to 825 HV_0.05; and the wear rate decreased from 3 × 10⁻⁵ g·m⁻¹·N⁻¹ to 1.19 × 10⁻⁵ g·m⁻¹·N⁻¹, illustrating that the wear resistance was greatly improved. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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12 pages, 5138 KiB

Open AccessArticle

Effects of Gd/Nd Ratio and Aging Treatment on Wear Behavior of Mg-Nd-Gd-Sr-Zn-Zr Alloys

by Ruotian Wang, Rongxiang Wang and Yongqiang Jia

Coatings 2024, 14(1), 7; https://doi.org/10.3390/coatings14010007 - 20 Dec 2023

Cited by 1 | Viewed by 1182

Abstract

The Mg-(4-x)Nd-xGd-0.3Sr-0.2Zn-0.4Zr (x = 0, 1, 2, and 3 wt%, Gd/Nd = 0, 1/3, 1, and 3) alloys were hot extruded and then aged (T5). The friction and wear properties of the as-extruded and as-aged alloys were studied using a ball-on-disk wear testing [...] Read more.

The Mg-(4-x)Nd-xGd-0.3Sr-0.2Zn-0.4Zr (x = 0, 1, 2, and 3 wt%, Gd/Nd = 0, 1/3, 1, and 3) alloys were hot extruded and then aged (T5). The friction and wear properties of the as-extruded and as-aged alloys were studied using a ball-on-disk wear testing machine and a scanning electron microscope to reveal the impacts of the Gd/Nd ratio and aging treatment. The results show that the friction coefficient of the as-extruded alloys increases first and then decreases with increasing Gd/Nd ratio. After aging, the friction coefficient of the alloys decreases slightly. The Gd/Nd ratio has no significant effect on the wear rate of the as-extruded alloys, and the wear rate decreases first and then increases with the increase in the Gd/Nd ratio for the as-aged alloys. The T5 alloy with a Gd/Nd ratio of 1/3 has the best wear resistance. The wear mechanisms of alloys mainly include abrasive wear, oxidation wear, and delamination wear. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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12 pages, 15801 KiB

Open AccessArticle

Microstructure, Texture, and Anisotropic Properties of High-Strength Low-Alloy Steel

by Yangxin Wang, Aijun Li, Chundong Hu, Xiaofei Guo, Xufei Li, Wenzhen Bi, Xicheng Wei and Han Dong

Coatings 2023, 13(8), 1442; https://doi.org/10.3390/coatings13081442 - 16 Aug 2023

Cited by 3 | Viewed by 1774

Abstract

The effects of cold rolling reduction rates and recrystallization annealing temperature on the microstructure, texture, and anisotropic properties of high-strength low-alloy (HSLA) steel were investigated using scanning electron microscopy and electron backscatter diffraction. The results revealed that the constituents of recrystallized, substructured, and [...] Read more.

The effects of cold rolling reduction rates and recrystallization annealing temperature on the microstructure, texture, and anisotropic properties of high-strength low-alloy (HSLA) steel were investigated using scanning electron microscopy and electron backscatter diffraction. The results revealed that the constituents of recrystallized, substructured, and deformed structures were strongly affected by cold rolling reduction rates ranging from 33.3% to 66.7% and recrystallization temperatures ranging from 780 to 840 °C. At an annealing temperature of 820 °C, when the cold rolling reduction rate was 33.3%, HSLA steel exhibited a low percentage of recrystallization, with cubic, γ-linear, rolled, and Z-texture (the texture at Euler angles φ1 = 30° and Φ = 20°–30°) structures. The rolled texture and Z-texture increased the strength anisotropy and disappeared at high cold rolling reduction rates. When the annealing temperature was increased from 780 °C to 820 °C, the proportion of recrystallized grains increased, the rolling texture disappeared, and grain orientation gradually gathered in the cubic texture and γ line texture, resulting in low anisotropy of strength. At an annealing temperature of 840 °C, the deformation of the grain disappeared; however, the anisotropy increased compared to annealing at 820 °C because of the formation of a new texture of {001}<−1–20>. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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24 pages, 6909 KiB

Open AccessReview

Research Status and Development Trend of Wire Arc Additive Manufacturing Technology for Aluminum Alloys

by Pan Dai, Ao Li, Jianxun Zhang, Runjie Chen, Xian Luo, Lei Wen, Chen Wang and Xianghong Lv

Coatings 2024, 14(9), 1094; https://doi.org/10.3390/coatings14091094 - 28 Aug 2024

Cited by 4 | Viewed by 2917

Abstract

It is difficult for traditional aluminum alloy manufacturing technology to meet the requirements of large-scale and high-precision complex shape structural parts. Wire Arc additive manufacturing technology (WAAM) is an innovative production method that presents the unique advantages of high material utilization, a large [...] Read more.

It is difficult for traditional aluminum alloy manufacturing technology to meet the requirements of large-scale and high-precision complex shape structural parts. Wire Arc additive manufacturing technology (WAAM) is an innovative production method that presents the unique advantages of high material utilization, a large degree of design freedom, fast prototyping speed, and low cast. As a result, WAAM is suitable for near-net forming of large-scale complex industrial production and has a wide range of applications in aerospace, automobile manufacturing, and marine engineering fields. In order to serve as a reference for the further development of WAAM technology, this paper provides an overview of the current developments in WAAM both from the digital control system and processing parameters in summary of the recent research progress. This work firstly summarized the principle of simulation layering and path planning and discussed the influence of relative technological parameters, such as current, wire feeding speed, welding speed, shielding gas, and so on. It can be seen that both the welding current and wire feeding speed are directly proportional to the heat input while the travel speed is inversely proportional to the heat input. This process regulation is an important means to improve the quality of deposited parts. This paper then summarized various methods including heat input, alloy composition, and heat treatment. The results showed that in the process of WAAM, it is necessary to control the appropriate heat input to achieve minimum heat accumulation and improve the performance of the deposited parts. To obtain higher mechanical properties (tensile strength has been increased by 28%–45%), aluminum matrix composites by WAAM have proved to be an effective method. The corresponding proper heat treatment can also increase the tensile strength of WAAM Al alloy by 104.3%. In addition, mechanical properties are always assessed to evaluate the quality of deposited parts. The mechanical properties including the tensile strength, yield strength, and hardness of the deposited parts under different processing conditions have been summarized to provide a reference for the quality evaluation of the deposition. Examples of industrial products fabricated by WAAM are also introduced. Finally, the application status of WAAM aluminum alloy is summarized and the corresponding future research direction is prospected. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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46 pages, 12698 KiB

Open AccessReview

A Review—Effect of Accelerating Methods on Gas Nitriding: Accelerating Mechanism, Nitriding Behavior, and Techno-Economic Analysis

by Yu-Long Zhou, Fan Xia, Ai-Jun Xie, Hao-Ping Peng, Jian-Hua Wang and Zhi-Wei Li

Coatings 2023, 13(11), 1846; https://doi.org/10.3390/coatings13111846 - 27 Oct 2023

Cited by 8 | Viewed by 5048

Abstract

Gas nitriding, as a surface modification technology to improve the wear resistance of workpiece surfaces, is widely used in wind turbine gears, pressure vessel gears, high-precision die casting abrasives, and other areas. However, the gas nitriding time is too long, reaching 40–60 h, [...] Read more.

Gas nitriding, as a surface modification technology to improve the wear resistance of workpiece surfaces, is widely used in wind turbine gears, pressure vessel gears, high-precision die casting abrasives, and other areas. However, the gas nitriding time is too long, reaching 40–60 h, which reduces the efficiency of nitriding and hinders the development of gas nitriding. Therefore, various accelerating methods are born accordingly. This review first introduces the basic principle, microstructure, and process parameters of conventional gas nitriding. Then, five common accelerating methods are summarized: process parameter optimization, surface mechanical nano-crystallization, surface-active catalysis, surface pre-oxidation, and surface laser treatment. Then, the effect of acceleration methods on gas nitriding is analyzed for the acceleration mechanism, nitriding behavior, and nitriding efficiency. Finally, the technical economy of the acceleration methods is compared for three aspects: energy consumption, carbon dioxide emission, and cost. And, the technical maturity of the acceleration methods is compared according to technology readiness level (TRL) technology. Based on the above content, the advantages and disadvantages of the five accelerating methods are reviewed, and the concept of a multi-technology collaborative processing acceleration method is proposed. Full article

(This article belongs to the Special Issue Advancement in Heat Treatment and Surface Modification for Metals)

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