Metals

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11 pages, 4303 KiB

Open AccessArticle

Vacuum Brazing of Dissimilar Al 7075 and Al–25 Si Alloy

by Dashuang Liu, Ping Wei, Weimin Long and Wei Zhou

Metals 2022, 12(6), 1042; https://doi.org/10.3390/met12061042 - 18 Jun 2022

Cited by 1 | Viewed by 1952

The vacuum brazing of dissimilar Al 7075 and Al–25 Si alloy was investigated. The brazing filler was copper foil with a thickness of 20 μm, and the brazing temperature was 560 °C held for 10 min. The average shear strength of the brazed [...] Read more.

The vacuum brazing of dissimilar Al 7075 and Al–25 Si alloy was investigated. The brazing filler was copper foil with a thickness of 20 μm, and the brazing temperature was 560 °C held for 10 min. The average shear strength of the brazed joint of dissimilar Al 7075 and Al–25 Si alloy was 26.4 MPa. The copper layer was found to be dissolved completely, and the interface of the joint had an irregular shape with a serrated border, indicating a good metallurgical bonding between the two dissimilar alloys. However, factors which might cause deterioration of the shear strength were also observed, including the formation of the intermetallic compounds such as MgZn₂, Cu₂Al and Mg₂Si, the existence of voids and microcracks, the coarsening of grains in Al 7075, and the coarsening of primary Si in Al–25 Si alloy. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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10 pages, 2383 KiB

Open AccessEditor’s ChoiceArticle

A New Strategy for Dissimilar Material Joining between SiC and Al Alloys through Use of High-Si Al Alloys

by Yongjing Yang, Ayan Bhowmik, Jin Lee Tan, Zehui Du and Wei Zhou

Metals 2022, 12(5), 887; https://doi.org/10.3390/met12050887 - 23 May 2022

Cited by 1 | Viewed by 2565

Abstract

Joining metals and ceramics plays a crucial role in many engineering applications. The current research aims to develop a simple and convenient approach for dissimilar material joining between SiC and Al alloys. In this work, Al alloys with Si contents varying from 7 [...] Read more.

Joining metals and ceramics plays a crucial role in many engineering applications. The current research aims to develop a simple and convenient approach for dissimilar material joining between SiC and Al alloys. In this work, Al alloys with Si contents varying from 7 wt.% to 50 wt.% were bonded with SiC at a high temperature of 1100 °C by a pressure-less bonding process in a vacuum furnace, and shear tests were carried out to study the bonding strength. When using low-Si Al alloys to bond with SiC, the bonding strength was very low. The bonding strength of Al/SiC joints increased significantly through the use of high-Si Al alloys with 30 wt.% and 50 wt.% Si. The shear strength achieved (28.8 MPa) is far higher than those reported previously. The remarkable improvement in bonding strength is attributed to the suppression of brittle interfacial products and reduced thermal stresses. This research provides a new strategy for joining between SiC and a wide range of Al alloys through the use of high-Si Al alloys as the interlayers. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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12 pages, 5904 KiB

Open AccessArticle

Face Bend Property of 7N01-T4 Aluminum Alloy MIG Welded Joint by Using Different Welding Wires

by Ping Wei, Mingfang Wu, Dashuang Liu, Yun Liang and Ziqiang Zhao

Metals 2022, 12(5), 873; https://doi.org/10.3390/met12050873 - 20 May 2022

Cited by 1 | Viewed by 1921

Abstract

7N01-T4 aluminum alloy were welded into three layers by metal inert gas (MIG) welding, with ER5087 welding wire containing Zr and ER5356 welding wire without Zr, respectively. The microstructures and face bend properties of the ER5356 and ER5087 welded joints were investigated. The [...] Read more.

7N01-T4 aluminum alloy were welded into three layers by metal inert gas (MIG) welding, with ER5087 welding wire containing Zr and ER5356 welding wire without Zr, respectively. The microstructures and face bend properties of the ER5356 and ER5087 welded joints were investigated. The weld zone (WZ) of the ER5087 welded joint had a smaller grain size than that of the ER5356 welded joint. Two kinds of welded joints were not broken via the face-bend test. However, there were some small holes and microcracks on the surface of the ER5356 welded joint, and there were no obvious defects on the surface of the ER5087 welded joint. The face bending specimen metallography shows that the grains of the cover layer were elongated, and the grains of the bottom layer were extruded. The ER5087 welded joint had a better bending performance than the ER5356 welded joint due to the microstructure refinement of the WZ through adding Zr element in ER5087 welding wire. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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9 pages, 3706 KiB

Open AccessArticle

Feasibility Study on Deposition of Tribaloy T800 on Cobalt-Based L605 Using Micro-Laser-Aided Additive Manufacturing

by Lichao Cao, Li Zhang and Guijun Bi

Metals 2022, 12(4), 586; https://doi.org/10.3390/met12040586 - 30 Mar 2022

Cited by 1 | Viewed by 2437

Abstract

In this study, deposition of Tribaloy T800 on cobalt-based L605 substrate using micro-laser-aided additive manufacturing (micro-LAAM) was explored. The micro-LAAM process was studied to achieve sound integrity of the deposited layer. The microhardness and microstructure of the deposited Tribaloy T800 layer were investigated. [...] Read more.

In this study, deposition of Tribaloy T800 on cobalt-based L605 substrate using micro-laser-aided additive manufacturing (micro-LAAM) was explored. The micro-LAAM process was studied to achieve sound integrity of the deposited layer. The microhardness and microstructure of the deposited Tribaloy T800 layer were investigated. The results showed that the developed micro-LAAM process can achieve single-layer crack-free deposition of Tribaloy T800 onto cobalt-based L605 without pre-heating of the substrate. Surface roughness of Ra 8 μm was obtained, indicating that micro-LAAM can significantly improve the surface quality. Very high microhardness in the range of 818 to 1000 Hv was achieved. Cellular grains with very fine dendritic microstructure and Laves phase were observed in the deposited Tribaloy T800, which contributed to the high hardness. With all the results obtained, it can be concluded that it is feasible to deposit Tribaloy T800 on L605 substrate with micro-LAAM to achieve sound integrity and high hardness. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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13 pages, 6331 KiB

Open AccessFeature PaperArticle

Post-Processing of Cold Sprayed CoNiCrAlY Coatings on Inconel 718 by Rapid Induction Heating

by Yongjing Yang, Aprilia Aprilia, Kaiqiang Wu, Sung Chyn Tan and Wei Zhou

Metals 2022, 12(3), 396; https://doi.org/10.3390/met12030396 - 24 Feb 2022

Cited by 7 | Viewed by 2485

Abstract

Cold spray is a solid-state additive manufacturing process that has been increasingly used for restoration of damaged parts. Due to the nature of powder solid-state bonding, cold spray coatings usually possess pores in the microstructures. Heat treatment has been widely used as a [...] Read more.

Cold spray is a solid-state additive manufacturing process that has been increasingly used for restoration of damaged parts. Due to the nature of powder solid-state bonding, cold spray coatings usually possess pores in the microstructures. Heat treatment has been widely used as a post-processing method to reduce the porosity of cold sprayed coatings. However, it usually requires the whole component to be treated in the furnace and typically takes a few hours to finish the treatment. This study aims to develop a localized and rapid post-processing method for cold sprayed coatings. Multi-layer cold sprayed coatings of CoNiCrAlY on an Inconel 718 substrate were produced. Then the coatings were heat treated at 800 °C, 900 °C, 1000 °C and 1100 °C by rapid induction heating. The porosity level of the coatings reduced significantly after induction heating for a short period of merely 10 min. This is attributed to the preferential Joule heating at pore regions, which results in pore closures within the coatings. The potential application of induction heating as a rapid post-processing method for cold spray coatings has been demonstrated in this work. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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21 pages, 4202 KiB

Open AccessFeature PaperArticle

Microstructure and Mechanical Properties of Laser Additive Manufactured H13 Tool Steel

by Karel Trojan, Václav Ocelík, Jiří Čapek, Jaroslav Čech, David Canelo-Yubero, Nikolaj Ganev, Kamil Kolařík and Jeff T. M. De Hosson

Metals 2022, 12(2), 243; https://doi.org/10.3390/met12020243 - 27 Jan 2022

Cited by 10 | Viewed by 5079

Abstract

Hot working tool steel (AISI H13) is one of the most common die materials used in casting industries. A die suffers from damage due to friction and wear during its lifetime. Therefore, various methods have been developed for its repair to save costs [...] Read more.

Hot working tool steel (AISI H13) is one of the most common die materials used in casting industries. A die suffers from damage due to friction and wear during its lifetime. Therefore, various methods have been developed for its repair to save costs to manufacture a new one. A great benefit of laser additive manufacturing (cladding) is the 3D high production rate with minimal influence of thermal stresses in comparison with conventional arc methods. Residual stresses are important factors that influence the performance of the product, especially fatigue life. Therefore, the aim of this contribution is to correlate the wide range of results for multilayer cladding of H13 tool steel. X-ray and neutron diffraction experiments were performed to fully describe the residual stresses generated during cladding. Additionally, in-situ tensile testing experiments inside a scanning electron microscope were performed to observe microstructural changes during deformation. The results were compared with local hardness and wear measurements. Because laser cladding does not achieve adequate accuracy, the effect of necessary post-grinding was investigated. According to the findings, the overlapping of beads and their mutual tempering significantly affect the mechanical properties. Further, the outer surface layer, which showed tensile surface residual stresses and cracks, was removed by grinding and surface compressive residual stresses were described on the ground surface. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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15 pages, 10938 KiB

Open AccessFeature PaperArticle

Effect of Interpass Temperature on Wire Arc Additive Manufacturing Using High-Strength Metal-Cored Wire

by Wengang Zhai, Naien Wu and Wei Zhou

Metals 2022, 12(2), 212; https://doi.org/10.3390/met12020212 - 24 Jan 2022

Cited by 25 | Viewed by 4486

Abstract

Wire arc additive manufacturing (WAAM) is suitable to fabricate large components because of its high deposition rate. In this study, a metal-cored low-alloy high-strength welding filler metal was used as feedstock. Single wall structures were prepared using the WAAM process with different interpass [...] Read more.

Wire arc additive manufacturing (WAAM) is suitable to fabricate large components because of its high deposition rate. In this study, a metal-cored low-alloy high-strength welding filler metal was used as feedstock. Single wall structures were prepared using the WAAM process with different interpass temperatures (150 °C, 350 °C, and 600 °C). No obvious microstructure change was observed when the alloy was deposited with the interpass temperatures of 150 °C and 350 °C. Electron backscattered diffraction analysis shows that that no significant texture is developed in the samples. The yield strength tends to decrease with the increase in interpass temperature; however, the influence is insignificant. The highest ultimate tensile strength is found at the interpass temperature of 350 °C. A higher interpass temperature can lead to a higher deposition rate because of the shorter waiting time for the cooling of the earlier deposited layer. It was found that the upper limit interpass temperature for WAAM of the low-alloy high-strength steel is 350 °C. When a higher interpass temperature of 600 °C was used, collapse of the deposited materials was observed. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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15 pages, 6185 KiB

Open AccessArticle

Effect of Spray Distance and Powder Feed Rate on Particle Velocity in Cold Spray Processes

by Rong Gen Neo, Kaiqiang Wu, Sung Chyn Tan and Wei Zhou

Metals 2022, 12(1), 75; https://doi.org/10.3390/met12010075 - 3 Jan 2022

Cited by 11 | Viewed by 3800

Abstract

Cold spray technology using micron-sized particles to produce coatings is increasingly used for reparative tasks in various industries. In a cold spray setup, the gun is usually connected to a robotic arm to deposit coatings on components with complex geometries. For these components, [...] Read more.

Cold spray technology using micron-sized particles to produce coatings is increasingly used for reparative tasks in various industries. In a cold spray setup, the gun is usually connected to a robotic arm to deposit coatings on components with complex geometries. For these components, the standoff distance used in the cold spray process has to be large enough for easy maneuverability of the gun around a small radial feature. However, a small standoff distance is commonly found in most studies, which is thought to prevent a velocity drop of the particles over a larger distance. Here, a study was carried out by measuring the Inconel 625 particle velocity at different spray distances, ranging from 3 to 40 cm. The highest average velocity of 781 m/s was found at a spray distance of 8 cm. Furthermore, a study with varying powder feed rates was also conducted. An increase in the powder feed rate was found to have a minimal effect on the particle velocity. Inconel 625 coatings deposited at the optimum standoff distance (8 cm) were found to have low porosity and high hardness. The results in this study demonstrate that a larger standoff distance can be applied without a significant drop in velocity for cold spray applications requiring high maneuverability. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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9 pages, 7927 KiB

Open AccessFeature PaperArticle

Inconel 713C Coating by Cold Spray for Surface Enhancement of Inconel 718

by Kaiqiang Wu, Sin Wei Chee, Wen Sun, Adrian Wei-Yee Tan, Sung Chyn Tan, Erjia Liu and Wei Zhou

Metals 2021, 11(12), 2048; https://doi.org/10.3390/met11122048 - 17 Dec 2021

Cited by 15 | Viewed by 3168

Abstract

Inconel 713C is a nickel-based superalloy usually considered as a material of poor weldability due to its susceptibility to hot cracking in the heat-affected zones. Cold spray, a solid-state deposition technology that does not involve melting, can be proposed as a methodology to [...] Read more.

Inconel 713C is a nickel-based superalloy usually considered as a material of poor weldability due to its susceptibility to hot cracking in the heat-affected zones. Cold spray, a solid-state deposition technology that does not involve melting, can be proposed as a methodology to deposit Inconel 713C for surface enhancement of other target components. In this study, Inconel 713C coating was deposited on Inconel 718 substrate with a high-pressure cold spray system. The coating was characterized in terms of microstructure, hardness, and wear properties. The cold-sprayed Inconel 713C coating has a low porosity level and refined grain structures. Microhardness of the Inconel 713C coating was much higher than the Inconel 718 substrate. The sliding wear tests showed that the wear resistance of the cold-sprayed Inconel 713C coating is three times higher than the Inconel 718 substrate, making the coating a suitable protective layer. The main wear mechanisms of the coating include oxidation, tribo-film formation, and adhesive wear. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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13 pages, 7982 KiB

Open AccessArticle

Effects of Isothermal Aging on Interfacial Microstructure and Shear Properties of Sn-4.5Sb-3.5Bi-0.1Ag Soldering with ENIG and ENEPIG Substrates

by Zhimin Liang, Fei Shen, Zongyuan Yang, Da Xu, Shaowei Wei, Zhenzhen Peng, Liwei Wang and Dianlong Wang

Metals 2021, 11(12), 2027; https://doi.org/10.3390/met11122027 - 14 Dec 2021

Cited by 1 | Viewed by 2256

Abstract

Sn–Sb system solders and ENIG/ENEPIG surface finish layers are commonly used in electronic products. To illustrate the thermal reliability evaluation of such solder joints, we studied the interfacial microstructure and shear properties of Sn-4.5Sb-3.5Bi-0.1Ag/ENIG and Sn-4.5Sb-3.5Bi-0.1Ag/ENEPIG solder joints after aging at 150 °C [...] Read more.

Sn–Sb system solders and ENIG/ENEPIG surface finish layers are commonly used in electronic products. To illustrate the thermal reliability evaluation of such solder joints, we studied the interfacial microstructure and shear properties of Sn-4.5Sb-3.5Bi-0.1Ag/ENIG and Sn-4.5Sb-3.5Bi-0.1Ag/ENEPIG solder joints after aging at 150 °C for 250, 500 and 1000 h. The results show that the intermetallic compound of Sn-4.5Sb-3.5Bi-0.1Ag/ENIG interface was more continuous and uniform compared with that of Sn-4.5Sb-3.5Bi-0.1Ag/ENEPIG interface after reflow. The thickness of the interfacial intermetallic compounds of the former was significantly thinner than that of the latter before and after aging. With extension of aging time, the former interface was stable, while obvious voids appeared at the interface of the latter after 500 h aging and significant fracture occurred after 1000 h aging. The shear tests proved that shear strength of solder joints decreased with increasing aging time. For the Sn-4.5Sb-3.5Bi-0.1Ag/ENEPIG joint after 1000 h aging, the fracture mode is ductile-brittle mixed type, which means fracture could occur at the solder matrix or the solder/IMC interface. For other samples of these two types of joints, ductile fracture occurred inside of the solder. The Sn-4.5Sb-3.5Bi-0.1Ag/ENIG solder joint was thermally more reliable than Sn-4.5Sb-3.5Bi-0.1Ag/ENEPIG. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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13 pages, 2679 KiB

Open AccessFeature PaperArticle

Hardening Efficiency and Microstructural Changes during Laser Surface Hardening of 50CrMo4 Steel

by Niroj Maharjan, Naien Wu and Wei Zhou

Metals 2021, 11(12), 2015; https://doi.org/10.3390/met11122015 - 13 Dec 2021

Cited by 8 | Viewed by 3461

Abstract

Laser surface hardening is an attractive heat treatment solution used to selectively enhance the surface properties of components by phase transformation. A quantitative parameter to measure the efficacy of hardening processes is still lacking, which hinders its application in industries. In this paper, [...] Read more.

Laser surface hardening is an attractive heat treatment solution used to selectively enhance the surface properties of components by phase transformation. A quantitative parameter to measure the efficacy of hardening processes is still lacking, which hinders its application in industries. In this paper, we propose a simple approach to assess the effectiveness of the process by calculating its thermal efficiency. The proposed method was applied to calculate the hardening efficiency during different laser processing conditions. This study revealed that only a small portion of supplied laser energy (approximately 1–15%) is utilized for hardening. For the same laser system, the highest efficiency is achieved when surface melting is just avoided. A comparative study showed that pulsed lasers are more efficient in energy utilization for hardening than continuous wave laser. Similarly, the efficiency of a high-power laser is found to be higher than a low-power laser and an increase in beam absorption produces higher hardening efficiency. The analysis of the hardened surface revealed predominantly martensite. The hardness value gradually decreased along the depth, which is attributed to the decrease in percentage of martensite. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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10 pages, 7313 KiB

Open AccessArticle

Induction Brazing for Rapid Localized Repair of Inconel 718

by Aprilia Aprilia, Jin Lee Tan, Yongjing Yang, Sung Chyn Tan and Wei Zhou

Metals 2021, 11(7), 1096; https://doi.org/10.3390/met11071096 - 10 Jul 2021

Cited by 5 | Viewed by 3332

Abstract

Vacuum furnace has been used for brazing repair of aerospace components, but it is a slow process which typically takes a few hours. The prolonged heating and cooling cycles could cause some adverse effects on the components such as excessive grain growth. A [...] Read more.

Vacuum furnace has been used for brazing repair of aerospace components, but it is a slow process which typically takes a few hours. The prolonged heating and cooling cycles could cause some adverse effects on the components such as excessive grain growth. A rapid brazing technique using induction coil was studied to evaluate its suitability for localized repair. Induction brazing of Inconel 718 was carried out using AMS 4777 brazing paste at different temperatures (950 °C, 1050 °C and 1150 °C ) for various durations (2 min, 10 min and 20 min). Microstructure and microhardness were evaluated. The experimental results show that brazing at 1050 °C leads to desirable microstructures in a short period of merely 2 min. The study demonstrates the potential application of induction brazing for rapid localized aerospace repair. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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17 pages, 6335 KiB

Open AccessArticle

Post-Processing of Cold Sprayed Ti-6Al-4V Coatings by Mechanical Peening

by Niroj Maharjan, Ayan Bhowmik, Chunwai Kum, Jiakun Hu, Yongjing Yang and Wei Zhou

Metals 2021, 11(7), 1038; https://doi.org/10.3390/met11071038 - 29 Jun 2021

Cited by 15 | Viewed by 3068

Abstract

Cold spray is an emerging additive manufacturing technology used in the aerospace industry to repair damaged components made of expensive metal alloys. The cold sprayed layer is prone to surface integrity issues such as high porosity and inadequate bonding at the substrate-coating interface, [...] Read more.

Cold spray is an emerging additive manufacturing technology used in the aerospace industry to repair damaged components made of expensive metal alloys. The cold sprayed layer is prone to surface integrity issues such as high porosity and inadequate bonding at the substrate-coating interface, which may cause premature failure of the repaired component. This study explored the use of mechanical peening as a post-processing method to improve the surface integrity of the cold sprayed component by modifying mechanical properties near the surface. Two mechanical peening processes, deep cold rolling (DCR) and controlled hammer peening (CHP), were utilized to improve cold sprayed Ti-6Al-4V coating on the Ti-6Al-4V substrate. Experimental results indicate that DCR and CHP increase the strength of the bond between the coating and substrate due to introduction of compressive residual stresses. In addition, porosity is also reduced by as much as 71%. The improvement is attributed to both the compacting effect of peening processes and the increment in the volume fraction of deformed regions. Full article

(This article belongs to the Special Issue Advances in Welding, Joining and Surface Coating Technology)

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