Diffusion Welding Research Articles

Effect of Laser Texturing Technology on Joint Properties of Ti to K9 Glass Diffusion Bonding

Effect of Laser Texturing Technology on Joint Properties of Ti to K9 Glass Diffusion Bonding

Review on the Solid-State Welding of Steels: Diffusion Bonding and Friction Stir Welding Processes

Solid-state welding (SSW) is a relatively new technique, and ongoing research is being performed to fulfill new design demands, deal with contemporary material advancements, and overcome welding defects associated with traditional welding techniques. This work provides an in-depth examination of the advancements in the solid-state welding of steels through diffusion bonding (DB) and friction stir welding (FSW). Considerable attention was given to DB of steel, which overcame the difficulties of segregation, cracking, and distortion stresses that are usually formed in liquid-phase welding techniques. The defects that affected DB included two types: two-dimensional defects of a metallic lattice, i.e., phases and grain boundaries, and three-dimensional defects, i.e., precipitation. FSW, on the other hand, was distinguishable by the use of relatively low heat input when compared to fusion welding processes such as tungsten inert gas (TIG), resulting in the formation of a limited heat-affected zone. Moreover, fine grain structures were formed in the FSW interface because of the stirring tool’s severe plastic deformation, which positively affected the strength, ductility, and toughness of the FSW joints. For instance, higher strength and ductility were reported in joints produced by FSW than in those produced by TIG. Nevertheless, the HAZ width of the specimens welded by FSW was approximately half the value of the HAZ width of the specimens welded by TIG. Some defects associated with FSW related to the diffusion of elements, such as C/Cr atoms, through the weld zone, which affected the local chemical composition due to the formation of rich/depleted regions of the diffused atoms. Moreover, the lack-of-fill defect may exist when inappropriate welding conditions are implemented. On the other hand, the stirring tool was subjected to extensive wear because of the high hardness values, which negatively affected the economical usage of the FSW process. A summary of the results is presented, along with recommendations for future studies aimed at addressing existing difficulties and advancing the solid-state technology for steel.

Interface microstructure and mechanical properties of copper/304 stainless steel dissimilar joint assisted by Ni transition layer using ultrasonic additive manufacturing (UAM)

The copper/304 stainless steel joints with high strength are obtained by preparing nickel transition layer on the steel surface using ultrasonic additive manufacturing (UAM) and pulsed TIG welding method. The results show that the addition of the nickel intermediate layer achieves metallurgical isolation between copper and steel, inhibits the infiltration of copper into steel grain boundaries and reduces joint stress, resulting in the formation of hybrid joints including fusion brazing (copper-nickel) and diffusion welding (nickel-steel). The weld and the vicinity of the interface are mainly composed of Cu-Ni solid solution and Ni-rich phase. The wavy texture produced by UAM on the nickel surface can form mechanical interlock at the interface to improve the joint strength, and finally all joints fracture near the fusion line on the copper side.

Customized blends of polypropylene for extrusion based additive manufacturing

AbstractFilament‐based material extrusion (MatEx) additive manufacturing has garnered great interest due to its simplicity, customizability, and cost‐effectiveness. However, MatEx of semicrystalline polymers is still largely relegated to prototyping applications. Major issues involving volumetric shrinkage and warpage of the printed parts must be addressed in order to employ them for printing functional parts. Moreover, the crystallization behavior and rheology of the polymer are dependent on the MatEx processing conditions. In the current work, the printability of blends of isotactic polypropylene with a soft, low crystallinity propylene based homopolymer is evaluated. Addition of the homopolymer resulted in an increase in the crystallization window of the blends by ~6°C that had a profound impact on the interlayer adhesion and residual stress state. The shear‐dependent melt flow behavior inside the printing nozzle as well as the interlayer chain diffusion and interlayer welding on the print bed were investigated. Rheological characterizations also indicate sufficient dispersion and miscibility of the homopolymer in the neat polypropylene matrix. The incorporation of the homopolymer as an additive significantly improved the dimensional accuracy of the printed parts through better dissipation of the entrapped residual stresses during MatEx. Moreover, the degree of mechanical anisotropy of the parts was significantly lower than that obtained using many 3D printable grade polymers. The findings from this study can be leveraged in toolpath planning, process parameter optimization, and new feedstock development, highlighting current limitations as well as providing valuable insights into necessary processing modifications in order to enable MatEx of next generation semicrystalline polymers.

Diffusion bonding of SiC ceramics with interlayers of metallic titanium foils and PVD titanium coatings

AbstractSilicon carbide (SiC) is a candidate material for high‐temperature structural aerospace applications due to its thermal and mechanical properties. Joining technologies enable the fabrication of complex shaped components needed for such applications. Various interlayers and processing conditions were used to form diffusion bonds between SiC substrates. Interlayers of titanium (Ti) foils and physically vapor deposited Ti coatings were used in the thicknesses of 10 and 20 μm with processing hold times of 1, 2, and 4 h. Polished cross sections of resulting diffusion bonds were analyzed using scanning electron microscopy (SEM) coupled with energy‐dispersive spectroscopy (EDS) and using transmission electron microscopy (TEM). From the TEM analysis, selected‐area diffraction patterns for Ti3SiC2, Ti5Si3Cx, and TiSi2 were observed. Moreover, TiC and an unknown phase were present in diffusion bonds formed with metallic titanium foil. From the SEM/EDS analyses, intermediate phases of Ti5Si3Cx and TiC were found to be present in microcracked diffusion bonds. With the thinner Ti interlayers and/or longer processing time, microcracking was alleviated or eliminated due to the presence of the more stable and lower thermal expansive phases of Ti3SiC2 and TiSi2. Detailed analysis of microstructures and the probable phases that formed in the bonded regions is presented.

Electrodeposited NiMo Alloy Coatings for Improved Molten Salt Compatibility

The use of molten halide salts as a primary coolant within next generation molten salt nuclear reactors (MSRs) has the potential to improve efficiency and nuclear reactor safety by operating at low pressures and high temperatures without boiling. However, these coolants will require the development of new corrosion resistant material systems that will have to meet or supersede existing standard codes for these systems. Therefore, new MSRs will require validation and testing of new material systems that can produce robust component structures and enable them to withstand these corrosive environments. Furthermore, any next generation process to apply protective coatings must allow for a conformal, thick, dense, and bonded material to be formed onto an ASME code approved material (e.g. type 316H stainless steel) that will comprise the structure of heat exchanger and containment vessel components.Within this context, Faraday Technology Inc. in collaboration with Oak Ridge National Lab and Quintus Technologies is working to develop and demonstrate the effectiveness of a low cost and high value corrosion-resistant alloy coating for next generation molten salt reactors. The manufacturing process involves the application of a functionally graded NiMo coating by electrodeposition onto 316H alloy substrates and their subsequent high temperature corrosion evaluation in molten fluoride salt at 700°C. After application the components were hot isostatically pressed (HIPped; at Quintus) to create a diffusion bond between the coating and alloy substrate. Initially, 316H alloy coupons were coated for evaluation (Figure 1 Left) in Mo capsules with static FLiNaK salt known to be corrosive due to metallic impurities. The next stage of testing involved evaluating coatings on the inner diameter of 316H tubes (25mm outer diameter; Figure 1 Middle). Coated tubes (75mm long) had coated endcaps welded to either end and were filled with the same FLiNaK salt and tested for 500 h at 700°C and 1000 h at 750°C. In addition, the microstructure and salt performance of butt welds were evaluated for joints between coated 316H tubes and joints between coated and uncoated 316H tubes. Results from the static capsule testing will be presented including the effect of coating composition and heat treating conditions on the depth of attack in the molten salt as feedback for the coating development process. The final phase of testing will include 200 mm long coated 316H tube sections in the hot and cold legs of a flowing FLiNaK thermal convection loop experiment which is currently being fabricated (Figure 1 R). Acknowledgements: The financial support of DOE Contract No. DE-SC0019602 is acknowledged. Figure 1: Corrosion characterization test plan. (Left) static coupon studies, (Middle) static pipe studies, and (Right) continuous flow loop pipe studies. Figure 1

Investigation of Diffusion Welding Capability of WC Ceramic Based Ni Doped Composites

In this study, sample pairs of (WC) Ni / (WC) Ni and WC-Ni / WC-Ni formed from (WC) Ni composites produced from Ni coated WC powders and uncoated WC-Ni / powders were used for diffusion welding. Diffusion welding was carried out by preloaded compression system under Ar atmosphere. Diffusion welding was obtained by changing bonding pressure and temperature. Schimadzu 100kN universal tensile machine was employed for tensile shear testing of diffusion welded couples. The tensile shear test results showed that electroless nickel coated WC(Ni) composite diffusion couples yielded best tensile shear load bearing capacity 35,4 MPa compared to other diffusion couples. Hardness values ranging from 200 to 400HV were determined. SEM and XRD analysis systems were used to analyze the microstructural analysis of the composites and diffusion welded samples obtained in the study and to analyze the particles formed at the weld interface.

Mechanical and Microstructural Characterization of the Bond Interface Formed in Diffusion Welding of CoCrNi Medium Entropy Alloy (MEA) and AISI 304 Stainless Steel Under Various Processing Parameters

Mechanical and Microstructural Characterization of the Bond Interface Formed in Diffusion Welding of CoCrNi Medium Entropy Alloy (MEA) and AISI 304 Stainless Steel Under Various Processing Parameters

Corrosion Resistance of Mg/Al Vacuum Diffusion Layers

This study used a vacuum diffusion welding process to weld magnesium (Mg1) and aluminum (Al1060). The diffusion layers, with different phase compositions, were separated and extracted by grinding. The diffusion layers’ microstructures and phase compositions were analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Furthermore, the corrosion resistance of each diffusion layer and the substrates were investigated and compared by performing corrosion immersion tests and linear polarization measurements in a 3.5 wt.% NaCl solution. The results showed that diffusion layers consisting of Mg2Al3, Mg17Al12, and Mg17Al12/Mg-based solid solutions were formed at the interface of the Mg1/Al1060 vacuum diffusion joint. Furthermore, each diffusion layer’s structure and morphology were of good quality, and the surfaces were free from defects. This result was obtained for a welding temperature of 440 °C and a holding time of 180 min. The corrosion current density of Mg1 was 2.199 × 10−3 A/cm2, while that of the Al1060, Mg2Al3, Mg17Al12, and Mg17Al12/Mg-based solid solutions increased by order of magnitude, reaching 1.483 × 10−4 A/cm2, 1.419 × 10−4 A/cm2, 1.346 × 10−4 A/cm2, and 3.320 × 10−4 A/cm2, respectively. The order of corrosion rate was Mg1 > Mg17Al12 and Mg-based solid solution > Mg2Al3 > Mg17Al12 > Al1060. Moreover, all diffusion layers exhibited an improved corrosion resistance compared to Mg1. This was especially the situation for the Mg2Al3 layer and Mg17Al12 layer, whose corrosion resistances were comparable to that of Al1060.

Parametric Optimization of Diffusion Welding Process in Joining of CoCrNi Medium-Entropy Alloys (MEA) and SUS 304 Stainless Steel Using Full Factorial Design

Parametric Optimization of Diffusion Welding Process in Joining of CoCrNi Medium-Entropy Alloys (MEA) and SUS 304 Stainless Steel Using Full Factorial Design

Diffusion Bonding of Al7075 to Ti-6Al-4V by Spark Plasma Sintering and Using a Copper Interlayer

Sheets of aluminum 7075 and titanium Ti-6Al-4V alloys were successfully joined using the spark plasma sintering (SPS) process. A copper foil was placed as an interlayer between the two surfaces. The bonding was made at 480 °C, 500 °C, and 520 °C with a holding time of 10 min and under a uniaxial pressure of 5 MPa and 10 MPa. The obtained bonds were analyzed by scanning electron microscopy, energy dispersive spectroscopy (SEM/EDS), and wavelength dispersive spectroscopy (WDS). It was found that copper diffused away through Al7075 and formed Al2Cu intermetallics but was not present at the joint region. The investigation of the fractured surfaces using X-ray diffraction (XRD) showed that the joint region contained TiAl3, TiAl2, and Ti3Al intermetallic compounds. The presence of the Cu foil was believed to hinder the formation of Al3Ti observed in previous studies by allowing more Ti to diffuse into the Al side.

Thermal Conductivity of NI HTS Coil Fabricated by Diffusion Bonding Technique

The no-insulation (NI) winding technique shows superior thermal protection performance when quenching of a high- temperature superconducting (HTS) coil occurs compared to the insulation winding technique. However, the thermal conductivity of an NI HTS coil are not clearly known because the HTS tape has various surface conditions such as roughness and oxidation. In this study, the diffusion bonding technique was applied to predict the thermal conductivity of an NI HTS coil, and the core of this technique is to remove the interface between turns by applying Ag diffusion bonding. To investigate the thermal conductivity of an NI HTS coil, an NI HTS coil was fabricated using a diffusion bonding technique, and a stainless-steel 304 block was fabricated to verify the experimental results. The thermal conductivity of the NI coil was measured using a conduction cooling experimental apparatus by applying heat loads to the outside of the coil. The measured thermal conductivity was compared to the values calculated using the thermal resistance circuit at temperatures from 20 K to 77 K.

Двухконтурный рекуперативный теплообменный аппарат с межканальным движением теплоносителя в металлических сетчатых материалах

The paper considers a dual-circuit recuperator using the principle of interchannel movement of coolant through a porous metal mesh. This interchannel coolant movement schematic and the metal mesh manufactured via vacuum diffusion welding of woven metal meshes form the basis for developing compact high-performance recuperators for aircraft. Employing porous metal mesh materials characterised by a well-developed heat exchange surface and transitioning from conventional longitudinal coolant movement within channels to interchannel coolant movement through metal meshes are the factors that ensure operation at low Reynolds numbers and maximum heat exchange efficiency. The principle of interchannel coolant movement combined with the intermesh coolant movement within the metal mesh yields a highly efficient porous heat exchange path, leading in turn to developing a recuperator featuring interchannel coolant movement that will enable greater heat exchange efficiency than that provided by the best finned heat exchangers.

Дослідження фазоутворення після дифузійного зварювання у вакуумі з’єднання нікель-ніобій

Diffusion welding is the ideal solution for joining dissimilar materials. This method is particularly effective if you should get a strong monolithic joint without the formation of a rough weld or solder seam. It is used if it is impossible to use standard fasteners. The main scope of this type of welding is the area of high technologies - aviation, space and other types of heavy engineering. All the advantages make the process indispensable under certain conditions and classify it as a high-tech type. This paper considers compounds of dissimilar metals nickel-niobium. In connection with the formation of many intermetallic compounds between these metals, the technology of diffusion welding in a vacuum was chosen. This method allows you to connect materials without melting due to the mutual diffusion of the components. The welding parameters affect the phase formation of the diffusion zone. To study the phase composition, a method of microstructural, X-ray microanalysis, as well as a state diagram of nickel-niobium, is proposed. When studying the weldability of the nickel-niobium system, samples were made in the form of a cube with a side of 10 mm, which was clamped in a mandrel and filled with Wood's alloy. The samples were not subjected to digestion, since during the polishing process, due to the different hardness of the phases, the structure turned out to be thermal polishing. The proposed scheme made it possible to study in detail the phase composition of individual layers of the diffusion zone, their dimensions and dependence on welding parameters. According to the results of quantitative X-ray microanalysis, we did not obtain accurate data on the phase composition and extent of diffuse layers. Qualitative X-ray spectral microanalysis, which was carried out by continuous scanning with an electron probe through the diffuse zone, made it possible to fix the phase reflections on the concentration curves and to determine the extent of the diffusion layers. For a more visual representation of the arrangement of the phases, a combined nickel-niobium diagram with a concentration curve is considered. The studies carried out made it possible to obtain a high-quality joint with mechanical properties that ensure reliability under operating conditions.

Особливості формування дифузійної зони з’єднання платина-титан

This paper considers the possibility of obtaining a high-quality titanium-platinum compound. Difficulties in joining dissimilar metals lie in the fact that during their interaction, brittle intermetallic compounds are formed, which cause the destruction of the product during the operation. Hard-phase welding methods are used to control the thicknesses and dimensions of intermetallic inclusions. Vacuum diffusion welding was chosen as the technology. To determine the formation of phases in the diffuse zone, the phase diagram of Ti-Pt was analyzed. The possible types of interactions between the components were determined. It is determined that the formation of a welded joint occurs due to the formation and growth of a diffusion zone in platinum and titanium. During welding, the growth of intermetallic phases Ti3Pt, TiPt, TiPt3, as well as solid solution zones, is observed. Microsections were made, on which the microstructure of the platinum-titanium compound was studied and microhardness measurements were carried out. The total width of the transitional diffusion layer is determined. The studies carried out made it possible to establish the sequence of the phase components of the diffusion zone. The use of the DRON 1.5 diffractometer made it possible to identify the phases. X-ray diffraction maxima and calculation of line identification established the presence of intermetallic compounds and their mixtures with solid solutions. The following methods were used in the work: microstructural analysis, microhardness measurement, the determination of the phase composition. A special technique was used to obtain high-quality microsections. During long-term grinding in the diffusion zone, a degree is formed due to the different properties of titanium and platinum. The phase composition of the platinum-titanium compound and the extent of each zone were established. The experiments carried out indicate that pressure, temperature and exposure time affect the quality of the joint. By changing these welding parameters, it is possible to change the microstructure of the diffusion zone. To determine the mechanical properties, a tear test was performed. For this, special three-metal samples were made. Determination of the mechanical properties made it possible to establish by what parameters the platinum-titanium compound meets the requirements of operation.

First‐Principles Exploration of 2D Benzenehexathiolate Coordination Nanosheets for Broadband Electrochromic Devices

AbstractElectrochromic materials can tune the illumination and heat exchange of a building with the environment and thereby save energy in lighting, heating, and air conditioning in a cost‐effective way, which is vital in realizing carbon neutrality. 2D frameworks such as coordination nanosheets (CONASHs) that are widely explored for a wide range of applications in energy storage and conversion can be a cluster of novel electrochromic materials. In this work, a series of transition metal benzenehexathiol (TM‐BHT) CONASHs are theoretically investigated via first‐principles simulations. During ion intercalation and deintercalation in TM‐BHTs, changes in lattice structures, lithium diffusion barriers, atomic charges, bond strength, and electronic properties are explored in‐depth. The incurred changes are then correlated with critical electrochromic properties, including the transmittance adjustment ranges in the visible light, near‐infrared, solar spectrum, and mid‐infrared. Among the various TM‐BHT systems, Cu‐BHT and Ag‐BHT are the most promising broadband electrochromic materials for optical and thermal management in the wavelength range from visible to mid‐infrared. The theoretical guidance from this work paves a new path toward electrochromic applications of CONASHs that exploit the versatility of these 2D materials.

Characterization of Joints Produced by Diffusion Bonding

The present study reports on the preparation of diffusion joint of Al 2024 sheets with and without hematite interlayer. Parameters like holding time, temperature and pressure were considered for producing the joint. Samples were prepared at a temperature of 400 °C while varying load (90 and 110 kN). The time duration of applying load was selected as 25 and 35 min. Microstructural characterization using scanning electron microscopy was carried out for analyzing microstructure of the joint. EDS spectrum was used to analyze the elemental composition of the joint. Hardness tests were employed to find the micro-hardness of the prepared joint using Vickers hardness tester.

Challenges and Latest Developments in Diffusion Bonding of High-Magnesium Aluminium Alloy (Al-5056/Al-5A06) to Stainless Steels

The aim of this work was to investigate the challenges associated with bonding Al-Mg alloys and develop a new method for bonding these alloys to steels. During an extensive R&D project, over 80 attempts, using 11 methods, were made to bond Al-6 wt.% Mg alloy (Al-5056/Al-5A06) to two types of stainless steels (heat-resistant 1Cr18Ni9Ti and conventional 316). Wide ranges of temperature (500 °C to 580 °C), pressure (0.5 MPa to 10 MPa) and time (1 min to 2 h) were used when direct diffusion bonding of these alloys. Then, effects of using various interlayers and brazing foils were investigated. The interlayers used in this work were gallium, pure titanium, copper and aluminium foils, aluminium 6061 alloy sheets, aluminium-silicon brazing foils, zinc and zinc alloy foils as well as an active brazing foil (known as Incusil-ABA containing silver, copper, indium and titanium). Several complex and multi-stage processes, using up to 3 different interlayers in the same joint, were also developed and assessed. Examination and assessment of the bonded samples, including failed attempts, paved the way of developing new methods for bonding these dissimilar materials. A number of samples with tensile strengths from 200 MPa to 226 MPa were made by using complex combinations of 2 or 3 interlayers and triple-stage bonding cycles. The highest recorded bond strength was 226 MPa in the as-bonded condition. This value is above the measured yield strength (134 MPa) and about 93% of the measured ultimate strength (243 MPa) of the parent Al-Mg alloy after it was subjected to the same bonding cycle. Since the use of complex processes was not feasible for bonding large components, a simpler and more practical bonding cycle was also developed in the project. Using the simpler process, joints with tensile strengths around 90 MPa could be made. This article also sheds light on the difficulties associated with brazing and soldering aluminium alloys with a high magnesium content.

Практическое использование результатов исследований технологических процессов формирования твердофазных соединений проволок в контролируемой газовой среде при создании листовых пористых сетчатых материалов с заданными свойствами

A specific feature of the structure-forming elements used for the manufacture of porous mesh materials is a high specific surface area and a complex configuration of wire meshes, which excludes the possibility of using wire cutting for welding. The research shows that cleaning in Freon-113 is an effective way to remove mineral oils, paraffins, fats and some other contaminants from the mesh surface, since this solvent is stable, non-flammable, non-explosive and does not interact with the workpiece material. In addition, improving the quality of mesh cleaning is achieved by superimposing ultrasonic vibrations in the range of 20...40 kHz. The study introduces flow layouts for the porous materials manufacture by pressure welding of wire meshes from steel 12Kh18N10T and titanium alloy VT2. Findings of the research show that welding envelopes of meshes made of steel I2XI8HI0T by rolling in evacuated makes it possible to obtain porous elements with sufficiently high mechanical and technological properties. It is possible to implement this process on any sheet rolling mill, which is its significant advantage. The paper gives the modes of welding by rolling and diffusion welding of meshes in the manufacture of porous materials. Within the study, we developed a mathematical model that makes it possible to predict the ultimate interlaminar strength for given values of technological parameters of the processes for manufacturing sheet blanks. It is proposed to control the interlayer strength by comparing the calculated data and the results of testing the samples for separation in accordance with the developed methodology. It is advisable to evaluate the control of strength, plasticity in the sheet plane and their anisotropy by comparing the calculated data and the results of testing specimens under conditions of biaxial tension, implemented during hydrostatic buckling through a round matrix.

Solid-State Diffusion Welding of Commercial Aluminum Alloy with Pure Copper

The aim of this investigation is to study the effect of time and temperature on the solid-state diffusion welding of commercial aluminum alloy 2xxx series with a pure copper at 425°C, 475°C, 500°C, and 525°C during holding times from 15 min to 240 min. The main characterization techniques were optical microscopy, scanning electron microscopy, energy dispersive spectrometry, nanoindentation, microhardness measurements, and x-ray diffraction. Results showed that increasing the temperature and the holding time had an effect on the apparition of the intermetallics at the Al alloy/Cu interface. Five intermetallic phases namely Al2Cu, AlCu, Al3Cu4, Al2Cu3, and Al4Cu9 were identified at the interface. The mechanical properties of the welded joint Al/Cu alloy varied also with the time and temperature. The nanoindentation measurements showed that the highest values of hardness were recorded in AlCu and Al3Cu4 phases. The welding success of these dissimilar metals can be used for battery cables or to form heat exchanger plates for vehicles.