Brazing Of Ceramics Research Articles

Competitive correlation between the interface layers determines the shear strength in Kovar/AgCuTi/Si3N4 joints

AbstractAs a promising high‐thermal‐conductivity ceramics, the direct bonding of Si3N4 with metals remains challenging. Here, we employed active metal brazing of Si3N4 ceramics and Kovar alloys using AgCuTi metal filler, and found that the shear strength in the prepared Kovar/AgCuTi/Si3N4 joints depends on the competitive correlation between the interface layers. The competitive consumption for active element Ti by Kovar/AgCuTi interfacial reactions reduced AgCuTi/Si3N4 interface layer thickness and deteriorated final shear strength, even when using a high‐Ti‐content filler. Surface analysis indicated that interfacial fracture between Ag‐based solid solution and Ti5Si3 was the primary cause of failure. Density functional theory (DFT) revealed that Ag (111)/Fe2Ti (001) interface had higher ideal work of adhesion (Wad) than Ag (111)/Ti5Si3 (001) interface, confirming the importance of AgCuTi/Si3N4 interface layer. Ultimately, by adjusting interface reaction layer thickness, the joints reached a high shear strength of 154.3 MPa.

Exploring bonding temperature variations in diffusion brazing of B4C ceramics with Ni-Cr-Si-Fe-B interlayer: Mechanical and microstructural analysis

This study examines the impact of the bonding temperature parameter on the quality of diffusion brazing joints of B4C ceramics using a Ni-Cr-Si-Fe-B interlayer. Various factors including shear strength, hardness, microstructure, interfacial phenomena, elemental diffusion patterns, formed compounds and phases, and fracture surfaces of the samples were analyzed and compared. The brazed sample at 1110 °C for 1/2 h exhibited the highest shear strength of 62 MPa. Increase of the bonding temperature to the optimum level (1090–1110 °C) enhances the fluidity of the molten interlayer, facilitating its diffusion into the porosities of the ceramic components. This increase also promotes higher interactions within the system, creating favorable conditions for element diffusion. However, surpassing the optimum temperature (1110–1130 °C) may lead to increased destructive reactions and intensify the impact of the coefficient of thermal expansion (CTE) mismatch, resulting in residual stresses and a subsequent decrease in bond strength. The excessive increase in the bonding temperature (1130–1150 °C) can lead to the excessive fluidity of the molten interlayer, potentially causing effusion onto the joint's fixture and damaging the samples. The results indicate the formation of various compounds between the elements of the interlayer and carbon and boron elements, including SiC, Ni4B3, CrB2, Fe2B, Ni6Si2B, and B2Fe3Ni3, at the fracture surface of the sample bonded at 1110 °C. The more substantial peaks of these compounds, compared to other samples, could be a reason for the higher strength of this particular sample.

Study of Ceramic Hollow Buoyant Balls Prepared Based on Slip Mold Casting and Brazing Process

In the domain of deep-sea buoyancy material applications, hollow ceramic spheres, known for their high strength and low mass-to-drainage ratio, contribute to increased buoyancy and payload capacity enhancement for deep submersibles, constituting buoyancy materials of exceptional overall performance. This study entails the brazing of two ceramic hemispherical shells, obtained through slurry molding, to form a ceramic float. This process, which integrates slurry molding and ceramic brazing, facilitates buoyancy provision. Further refinement involves welding a ceramic connector onto the ceramic shell, incorporating a top opening to create a ceramic float equipped with an observation window seat. The ceramic float maintains uniform wall thickness, while the observation window facilitates external environmental observation in deep-sea research. Two pressure-resistant spherical shells, produced using this process, underwent testing, revealing the wall thickness of the prepared alumina ceramic hollow spheres to be 1.00 mm, with a mass-to-drainage ratio of 0.47 g/cm3 and a buoyancy coefficient of 53%. The resultant ceramic hollow floating ball can withstand hydrostatic pressure of 120 MPa, while the pressure-resistant ball shell with an observation window seat can endure hydrostatic pressure of 100 MPa, ensuring safe operation at depths of 5000–6000 m. This process provides a production method for subsequent large-scale ceramic float manufacturing for the transportation of objects or personnel.

Engineering design and manufacturing of a radio frequency plasma driver without Faraday shield for NBI application

A radio frequency (RF) driven ion source is favorable for high-power and long-pulse neutral beam injection (NBI) system. To reduce the damage caused by the isotropic heat and particle fluxes from the plasma, the traditional RF plasma driver of the NBI ion source introduces a Faraday shield (FS) for protection. However, the simulations and experiments show that the FS seriously affects the RF coupling and around 50 % of the input power deposits on the FS. The water-cooled discharge tubes with a double-layer ceramic structure have been developed to avoid using the FS structure. It's expected to improve the RF power transfer efficiency and to promote the development of high-power and long-pulse RF ion source. To verify the feasibility of the double-layer ceramic structure, the paper has carried out the fluid-thermal-structural coupling analysis and the fracture mechanical analysis on two proposed types: the alumina ceramic brazing structure and the silicon nitride ceramic bonding structure. The sample tests and the prototype manufacturing have been completed. Preliminary tests of the plasma discharge on the prototype of the alumina ceramic brazing structure have been launched. A plasma discharge of 30 kW and 20 s have been achieved.

Reaction mechanism and mechanical properties of SiC joint brazed by in-situ formation of Ti3SiC2

This study undertakes vacuum pressureless brazing of SiC ceramics with TiSi2 powder, achieving MAX bonding. Microscopic characterization elucidates the microstructural evolution of the joined seam across various brazing temperatures and durations. The formation process of Ti3SiC2 is detailed through thermodynamic and kinetic analyses. At 1550 ℃ for 30 min or 1600 ℃ for 15 min, the filler undergoes in-situ reaction with SiC, yielding a dense, continuous Ti3SiC2 (MAX) phase, with no other phases observed. This suggests that increased temperature reduces MAX synthesis time. However, prolonged brazing causes voids in the center of the joined seam. Si volatilization was key for Ti3SiC2 in-situ formation, and this reaction equation was proposed. Maximum average shear strength at room temperature is 127.15 MPa at 1550 ℃ for 30 min and 118.15 MPa at 1600 ℃ for 15 min.

Femtosecond laser surface modification-based brazing of Si3N4 ceramics to 7A52 aluminum alloy

Femtosecond laser surface modification-based brazing of Si3N4 ceramics to 7A52 aluminum alloy

Rare earth oxide CeO2 enhanced reactive air brazing of YSZ ceramics

Cerium oxide (CeO2) in the range of 0–16 mol.% is used to enhance the joint of Ag-based filler for brazing yttria-stabilized zirconia (YSZ) ceramic in the air. Ag–CeO2 filler is first adopted to braze YSZ ceramic (3 mol.% yttria). The CeO2 is found to cluster at the interface of YSZ and Ag seam, improving the wetting behavior of Ag-based fillers. The maximum shear strength of YSZ joints can reach 35.1 MPa using Ag–1CeO2 fillers at 1050 °C/30 min. Moreover, CeO2 is used to enhance the Ag–CuO filler for brazing YSZ ceramic. As the increase of CeO2 content, the contact angle of Ag–CuO on the YSZ surface decreases first and then increases. The average shear strength could reach 76.5 MPa using Ag–CuO–8CeO2 at 1050 °C/30 min. The CeO2 could decrease residual stress by adjusting the linear expansion coefficient of Ag-based fillers. Therefore, this study provides a new strategy for exploring air brazing fillers.

Study on Brazing of SiC Ceramics with Zr-Cu-Nb Filler Metal

Study on Brazing of SiC Ceramics with Zr-Cu-Nb Filler Metal

Joining of SiC ceramics using high-silicon aluminum alloy fillers assisted by laser cladding

A Si–40Al joining transition layer was prepared via laser cladding, followed by brazing of SiC ceramics using Si–60Al alloy as the joint filler. The microstructure, composition, and flexural strength of the brazed joints were investigated under different brazing temperatures and holding times. The corrosion resistance of the joints was evaluated using a hydrochloric acid immersion test. The laser cladding layer effectively reduced interfacial stress, enhanced interfacial bonding, and suppressed the formation of brittle intermetallic compounds. The main constituents of the brazed joint were Si, Al2O3, and SiC, with newly formed SiC at the interface promoting interfacial bonding. The flexural strength of the brazed joint held at 900 °C for 30 min exceeded 279 ± 13 MPa, equivalent to that of the SiC substrate. Compared to direct brazing of SiC using Si–60Al alloy filler and Si–40Al alloy filler, the strengths were increased by 49% and 94%, respectively. Furthermore, the joints exhibited excellent corrosion resistance, with a flexural strength of 177 ± 11 MPa after 10 h of hydrochloric acid immersion.

Brazing of Ti-coated SiC using a CoFeCrNiCu high entropy alloy filler via electric field-assisted sintering

Electric field-assisted sintering technology (FAST) was used to join SiC ceramic by using a CoFeCrNiCu high-entropy alloy filler. A thin Ti film was deposited on SiC surface by physical vapor deposition to reduce the residual thermal stress in the joint. The microstructure, bending strength, and bonding mechanism were systematically investigated. It was found that a discontinuous TiC layer could be formed at the interface and the interfacial reaction products changed with different brazing temperatures. A joint with a bending strength of 72 MPa was achieved at 1200 °C, which is 73% higher than that of the SiC brazed without Ti coating. This work provides a new insight in the interfacial design of ceramic brazing with high mechanical properties.

Process method of Si3N4 ceramic brazing sealed cavity for high-temperature application.

The process method of a Si3N4 ceramic sealed cavity is realized by vacuum brazing and chemical reaction at 1,100°C and 0.5 MPa pressure. Through the combination of Si3N4 ceramic polishing and thinning, inductively coupled plasma etching, and high-temperature metal filler (Ti-Zr-Cu-Ni) brazing process, a vacuum-sealed cavity suitable for high-temperature environments was prepared. The cross section of the bonding interface was characterized by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), which indicated that the two Si3N4 ceramic were well bonded, the cavity structure remained intact, and the bonding interface strength exceeded 5.13 MPa. Furthermore, it retained its strong bonding strength after in high-temperature environments of 1,000, 1,050, and 1,100°C for 1 h. This indicates that a brazed vacuum-sealed cavity can be used in high-temperature environments. Through the proposed method, pressure sensor that can withstand high temperatures can be developed.

Brazing SiC ceramics and Zr with CoCrFeNiCuSn high entropy alloy

CoCrFeNiCuSn high-entropy alloy and Cu foam composite interlayer was used as a filler for the brazing of SiC ceramics and Zr. The microstructure and mechanical properties of the brazed joint at room temperature and high temperatures as well as the brazing mechanism were systematically investigated. The microstructure is adjusted by controlling the brazing temperature. The main phases in the joint were identified at different brazing temperatures to be a high-entropy alloy phase, α-Zr (s, s), Zr2Cu, (Zr, Sn) and Zr(Cr, Fe)2 Laves phase. The joint brazed at 1040 °C for 20 min exhibited a maximum shear strength of 221 MPa at room temperature and an average shear strength of 207 MPa at 600 °C. The room temperature and high temperature-strength obtained here are much higher than those obtained for joints brazed using a conventional filler. Owing to the high-entropy effect, the joint matrix is mainly composed of solid solution phase, which improves the strength and thermal stability of the joint. The existence of the hard Zr(Fe, Cr)2 Laves phase and the soft α-Zr (s, s) phase in the joint significantly improves its strength and plasticity.

Application progress of high-entropy alloys in brazing field: A short review

Multi-component high-entropy alloys (HEAs) have intrigued intensive attentions in the metallic materials fields due to their unprecedented properties including excellent radiation resistance, exceptional strength-ductility synergy at cryogenic temperature and good high-temperature stability. As such, HEAs are promising candidates for many engineering applications in extreme environment. To promote the fabrication and application of HEAs, exploiting HEAs-brazing technique is indispensable due to its cost-effectiveness, simplicity and excellent adaptability to sample configuration. Besides, owing to high-entropy and sluggish diffusion effects, HEAs also can be used as brazing filler metals in the brazing technology. The short review first discusses the brazing of HEAs with different fillers, and the interfacial microstructures and joining properties are summarized. Subsequently, the brazing of traditional ceramics to themselves or to metals with novel HEA filler metals is introduced. Besides, the summary and expectation of the coming research topics are also listed in the conclusions.

Joining of SiC using CoFeCrNiCuTi high entropy alloy filler by electric current field assisted sintering

SiC ceramics were brazed by electric field-assisted sintering technology using CoFeCrNiCuTi high-entropy alloy as joining filler. The effect on the interface microstructure and bend strength of brazed joints at different brazing temperature was systemically studied. The interfacial reaction was controlled by adjusting the brazing temperature. The main components in the brazing seam are high-entropy alloys FCC (HEAF), C, TiC, CrC, and Cr23C6 phase. Furthermore, the maximum bending strength of 54 MPa was found when brazed at a lower temperature of 1125℃. In addition, due to the electric field-assisted sintering technology and the high-entropy effect of the CoFeCrNiCuTi filler, the diffusion of elements and the formation of solid solution were accelerated. This suggests that the current field was beneficial to improve the inter-diffusion between the CoFeCrNiCuTi filler and SiC ceramics. Consequently, the low-temperature rapid brazing of SiC ceramics was realized, and this technology provides a new filler system for ceramic brazing.

Realizing the air brazing of ZrO2 ceramics through Al metal

The exploration towards cost-effective filler metal for ceramics joining has always been the key issues for ceramics joining. Herein, we reveal that the Al metal prefers to spread on the ZrO2 based ceramic under the air heating condition, due to the geometric limit effects by in-situ formed dense Al2O3 surface. Inspired by this, the joining of ZrO2 based ceramics was realized in air with Al metal as filler, through the diffusion of Al towards ceramic side. The Al element can induce obvious interfacial bonding effect on Al2O3 layer and ZrO2 ceramic, where the hybridization among the Al-p, Zr-d and O-p orbitals plays a key role. The in-situ formed Al2O3 layer on Al filler surface is vital for forming the fine interface (shear strength of ∼36 MPa), which results in the relief of lattice mismatch and peak stress at ceramic-filler metal transition interface.

Brazing of ZrO2 Ceramics with Metallic Fillers Using Electrical Current

Brazing of ZrO2 Ceramics with Metallic Fillers Using Electrical Current

Manufacturing of high entropy alloy in the Ni-Nb-Co-Fe-Cr system by rapidly solidification method for oxide ceramic brazing

This paper presents results of research of high-entropy alloys of the Ni-Nb-Co-Fe-Cr system in the as-cast state and after rapid quenching from the melt. The results of experiments on obtaining a brazed joint of aluminum-oxide ceramics with using the filler metal of this system and the results of a studying this joint are presented. Differential thermal analysis (DTA), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray microanalysis (EDX) and measurement of microhardness were used as experimental research methods. The liquidus and solidus temperatures of high-entropy alloy Nb0.73CoCrFeNi2.1 were determined. The phase composition of alloys of the Ni-Nb-Co-Fe-Cr system was studied. It was shown, that alloys of this system can be used as filler metal to create a joint between ceramics. The microhardness of the brazed seam was studied. Based on these results the brazing mode for samples of aluminum-oxide ceramics with using high-entropy alloy Nb0.73CoCrFeNi2.1 as a filler metal was chosen.

Brazing of SiC ceramics pretreated by chromium coating using inactive AgCu filler metal

AbstractIn this work, chromium coating conducted by magnetron sputtering was introduced to braze SiC ceramics using inactive AgCu filler metal. The results showed that reliable metallurgical bonding of SiC ceramics was obtained at 900°C for 10 minutes. SEM, XRD, and TEM were used to identify the reaction phase in the joint, and the typical interfacial microstructure was SiC/mixed CrSi2 + Cr23C6 layer/CrSi2/Ag(s,s)+Cu(s,s)/CrSi2/mixed CrSi2 + Cr23C6 layer/SiC. The shear strength of SiC joint using chromium coating brazed with inactive AgCu filler metal was 29.6 MPa and the joint fractured at the SiC substrate entirely after shear test. The proposed active element coating method provides a feasible way to achieve the brazing of ceramics.

Wetting, Interfacial Interactions, and Vacuum Metallization of SnO2 Ceramics by Liquid Metals and Alloys

The wetting behavior of SnO2-ceramic substrates with metallic melts, such as Au, Ag, Cu, Sn, Ga, Pb, Ni, Al, Ge, Ag-Cu, Ag-Ge, Ag-Si, Cu-Si, Cu-Ni, Cu-Ge, Cu-Sn, Ag-Ti, Sn-Ti, Ag-Cu-Ti, and Cu-Sn-Ti in vacuum, was investigated. Wetting experiments at high temperatures (1270-1370 K) were carried out using sessile drop method with two types of SnO2 ceramics: low-density pure SnO2, and high-density SnO2 with 1 wt.% Fe2O3. Molten copper and its alloys with high Cu-concentration, such as Cu-Ag, Cu-Sn, and Cu-Ni, wet the ceramics, because SnO2 decomposes during heating in vacuum, resulting in formation of oxygen, which dissolves in the melt and acts as an adhesion-active additive. The dependence of the contact angle on the composition of the melt for various binary alloys (Ag-Cu, Ag-Si, Ag-Sn, Cu-Ni, Cu-Sn, and Cu-Si) was investigated. The results showed that the Cu-Ni system is the most promising filler for metallization and vacuum brazing of SnO2 ceramics. A method of vacuum metallization, using Cu-Ni filler, resulting in strong adhesion of coatings, which are uniformly deposited on the SnO2 ceramic surface, is proposed.

Active Brazing of SiC-Base Ceramics to High-Temperature Alloys

Active metal brazing of SiC-base ceramics and composites to Ti, Cu-clad-Mo, and nickel was carried out to screen promising commercial braze compositions with liquidus temperatures of 810-1040 °C. Microstructure, elemental composition, and microhardness were characterized using FESEM, EDS, and Knoop test in joints brazed using Ag-Cu-Ti alloys (Cusil-ABA and Ticusil) and a Ni-base alloy (MBF-20). Ti- and Si-rich interfacial layers developed in joints brazed using Ti-containing brazes, whereas Ni- and Si-rich layers formed in joints brazed using Ni-base brazes. Monolithic SiC/Mo and SiC/Kovar joints with Cusil-ABA had sound interfaces and compressive shear strengths of 25-30 MPa. In the case of composites, surface preparation influenced bond quality: ground SiC-SiC samples led to sound joints and unground samples led to interfacial decohesion at low thermal strains whereas joints cracked regardless of the surface preparation at large thermal strains. Among SiC-SiC/metal joints, SiC-SiC/Cu-clad-Mo had the best microstructure and bond quality. Microstructures of joints made using MBF-20 mixed with low-expansion Si-X (X: Y, Ta, Hf, Ti, B) eutectic powders to control the thermal expansion are also presented.