Diffusion Welding Research Articles

Friction Stir Welding Benefits Technique over Other Welding Techniques of Dissimilar Metals

Abstract: Due to the low heat input situation, solid state welding (SSW) has demonstrated higher potential for integrating a variety of equivalent and dissimilar material combinations. The temperature stays below the melting point of the source materials throughout the solid-state welding process. Compared to fusion welding, solid state welding offers the highest quality. Aeronautics, nuclear, space, and aviation are just a few of the industrial production sectors that utilize the solid-state welding technology. Diffusion welding, explosion welding, friction welding, forge welding, cold welding, role welding, hot pressure welding, and ultrasonic welding are just a few of the SSW techniques covered in the current article. This study looks at a variety of SSW kinds and solid-state welding applications. This study examines many types of SSW and the applications of solid-state welding. Current Study includes the pros and cons of other welding techniques over friction stir welding

The effect of diffusion welding parameters on the microstructural characteristics and mechanical properties of dissimilar joint between AISI 418 stainless steel and Inconel 738 superalloy using nickel interlayer

The effect of diffusion welding parameters on the microstructural characteristics and mechanical properties of dissimilar joint between AISI 418 stainless steel and Inconel 738 superalloy using nickel interlayer

Establishing theoretical foundations for predicting the structural and morphological characteristics of diffusion-welded joints of the beryllium–copper composite

The paper presents the results of theoretical and experimental studies regarding the quality of diffusion welding of the beryllium–copper composite. Numerical investigations of the parameters of heterodiffusion of diffusants and the thickness of the Be–Cu pair welded joint under varying temperature-time conditions were conducted. The analytical examinations revealed that the thickness of the diffusion weld at the Be–Cu joint varies between 26 and 345 µm, with the temperature increasing from 800 to 1000 °C and the holding time ranging from 20 to 120 min. The calculated layer thickness during the diffusion welding of a Be–Cu pair at 800 °C for 2 h is 65 µm, with 15 µm on the beryllium side and 50 µm on the copper side. Notably, a CuBe3 intermetallic compound zone can form in the diffusion weld, which should be considered an adverse factor that reduces the mechanical properties. To theoretically substantiate the modification of the structure and properties of the diffusion zone, a numerical study of welding was carried out using a 10 μm thick nickel foil spacer, which is readily soluble in beryllium. It was demonstrated that after exposure to temperature-time conditions at 900 °C for 20 min, a 50 µm wide diffusion-bonded joint is formed. Its structure includes two single-phase zones of solid solutions based on copper and beryllium, as well as two two-phase regions consisting of solid solutions hardened with intermetallic compounds. Since the weld lacks structural zones consisting solely of intermetallic compounds (unlike when welding the Be–Cu diffusion pair), there are grounds to anticipate a reduction in the embrittling effect on the weld. The results obtained from the analytical studies can serve as the foundation for a theoretical prediction method for assessing the quality of diffusion welding of the beryllium–copper composite.

Designing strong and ductile heterogeneous lamella-structured Mg alloy via diffusion bonding

Achieving superior strength-ductility synergy in Mg alloys is a critical issue for engineering applications. To address the trade-off between strength and ductility, the introduction of heterogeneous lamellar structures has recently proven be an effective strategy. In this study, we fabricated an AZ31/WE43/AZ31 alloy with heterogeneous lamellar structure using diffusion bonding (DB). Increasing the DB temperature enhanced the diffusion behavior, resulting in the precipitation and growth of Al2(Y, Nd) phases within the interfacial diffusion zone. Additionally, grain growth occurred, leading to a reduction in the heterogeneity of the grain size in individual AZ31 and WE43 layers. The sample fabricated at 460 °C, which exhibited relatively high heterogeneity and strong interfacial bonding, demonstrated a good combination of yield strength (202.4 MPa), ultimate tensile strength (315.8 MPa), and elongation (19.4 %). These mechanical properties significantly surpassed those of the original individual materials and exceeded the rule-of-mixture predictions. The excellent strength-ductility synergy observed in this alloy can be attributed to the presence of heterogeneous deformation-induced stress (HDI stress), which promotes extensive activation of non-basal dislocation slips. Furthermore, in-situ tensile tests demonstrated that the pile-up of geometrically necessary dislocations (GNDs) at the heterogeneous interface contributed to the superior HDI strengthening and HDI strain hardening. Overall, this study provides new insights into the fabrication of heterogeneous lamella-structured Mg alloys with strength-ductility synergy.

Effect of processing temperature on interface microstructure of diffusion welded joint of super-duplex stainless steel and zirconium alloy with nickel alloy interlayer

In the present study, super-duplex stainless steel (SDSS) and zirconium alloy (ZrA) was vacuum welded using nickel alloy (NiA) interlayer by the diffusion welding process. The welded joints were processed from 800 to 950 °C in steps of 50 °C using 4-MPa compressive load for 75 min. The joints were characterised using optical microscopy, scanning electron microscopy, electron probe micro-analyser, and x-ray diffractometer. The SDSS│NiA interface is planar in nature for all welding temperatures; however, layer-wise Ni5Zr, Ni10Zr7, NiZr, and NiZr2 reaction products were observed at the NiA│ZrA interfaces. The reaction products and width of these products increase with welding temperature. At both the interfaces, hardness values gradually increase with an increase in welding temperature. NiA│ZrA interface exhibited higher hardness as compared to the SDSS│NiA interface due to the presence of layer wise intermetallics. Joints reached a maximum tensile strength of ∼370 MPa (with an elongation of ∼7.9 %) when the joints were processed at 900 °C due to optimal reaction zone width and the least embrittling effect of the respective intermetallics. At lower temperatures, fracture surfaces of welded assemblies showed featureless morphology and voids present due to the poor coalescence of mating surfaces. At higher welding temperatures, the fracture surface of the transition joint preferred brittle fracture mode due to the cleavage planes with different alignments with insignificant volume fraction of voids on the fractography.

Study of the Quality of Thermal Diffusion Welding of Crystals in a Disk Optical Element by the Optoacoustic Method

Study of the Quality of Thermal Diffusion Welding of Crystals in a Disk Optical Element by the Optoacoustic Method

Diffusion Bonding 321-Grade Stainless Steel: Failure and Multimodal Characterization.

Vacuum diffusion-bonded printed circuit heat exchangers are an attractive choice for the high-temperature, high-pressure demands of next-generation energy applications. However, early reports show that the high-temperature materials desired for these applications suffer from poor bond strengths due to precipitation at the bond line, preventing grain boundary migration. In this study, a diffusion bond of the high-temperature stainless steel grade 321H is investigated, and poor mechanical properties are found to be caused by Ti(C, N) precipitation at the bond line. Through in situ studies, it is found that Ti diffuses from the bulk to the mating surfaces at high temperatures. The Ti subsequently precipitates and, for the first time, an interaction between Ti(C, N) and Al/Mg-oxide precipitates at the bond line is observed, where Ti(C, N) nucleates on the oxides forming a core-shell structure. The results indicate that small amounts of particular alloying elements can greatly impact diffusion bond quality, prompting further research into the microstructural evolution that occurs during bonding conditions.

Origins of HDI stress in copper–brass laminates with dual-heterostructured interfaces

In this work, a copper–brass hetero-laminate with dual-heterostructured interfaces was fabricated by diffusion welding in combination with cold deformation and annealing. These dual-heterostructured interfaces possess the characteristics of both gradient interface and sharp interface. The evolutions of geometrically necessary dislocations (GNDs) and local strains near these dual-heterostructured interfaces were investigated by in-situ and quasi in-situ tests. By employing a constitutive model, the evolutions of GND density and the HDI synergistic strengthening mechanism were systematically explored. The results demonstrated that the distribution of GNDs and local strains near the coarse/fine-grained interface exhibited a gradient feature, without any obvious concentrations of GNDs and strains, which can be attributed to the transition effect of the gradient interface. Furthermore, the density of sample-scale GNDs accumulated near the coarse/fine-grained interface was found to be at least one order of magnitude lower than that of grain-scale GNDs accumulated near grain boundaries. Both the constitutive model and experimental results confirmed that grain-scale GNDs serve as the primary origins of significant HDI stress, rather than the sample-scale GNDs.

Solid State Diffusion Bonding of Alumina with Aluminum Alloy

The objective of this work is to study the effect of time during the bonding process of alumina with an industrial aluminum 6060 alloy by the technique of solid-state welding at 600°C. Optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, corrosion tests, and microhardness measurements were used as characterization techniques. The extended time during the bonding process had an effect on the microstructure of the interface and its mechanical properties. Oxygen diffusion was detected across the aluminum alloy/alumina interface. A recrystallization reaction developed on the aluminum side during the bonding process, which affected the aluminum alloy hardness values. By bonding metal to ceramic, it allows the use of ceramics in automotive engines to reduce weight, increase thrust-to-weight ratio and operating temperature, and improve working efficiency.

Pressure Welding through a Layer of Hydrocarbon Material: Electromagnetic Phenomena during the Diffusion Bonding Formation

Pressure Welding through a Layer of Hydrocarbon Material: Electromagnetic Phenomena during the Diffusion Bonding Formation

Effects of mechanical heterogeneity and dislocation storage capacity on the strength–ductility synergy of heterostructured laminates

Heterostructured laminates have attracted significant attention in the materials community owing to their exceptional combination of strength and ductility. However, long-standing questions remain regarding the impact of the strength difference between the soft and hard layers on the synergistic strengthening in hetero-laminates with weak mechanical heterogeneity; the role played by soft/hard layers with various dislocation storage capacities on the strength–ductility synergy is also poorly understood. In this study, a series of typical heterostructured copper–brass laminates were fabricated using the diffusion welding + forging + rolling + annealing technique. The results demonstrated that larger microstructural and mechanical heterogeneities improved the strength–ductility combination of the hetero-laminates. The relatively weak mechanical heterogeneity and superior dislocation storage capacity of the soft copper and hard brass layers facilitated inter-layer synergistic deformation. This induced a gradual distribution of local strains and geometrically necessary dislocations (GNDs) near the hetero-interface. Thus, when evaluating the role of soft layers in synergistic strengthening, it is crucial to consider their generation and storage capabilities for dislocations.

Enhanced tensile strength of TiAl/Ti2AlNb diffusion bonding joint by a novel post-bonded hot deformation

Dissimilar TiAl-based alloys weld by solid-state bonding, also known as diffusion bonding (DB), usually show brittle intermetallic compounds, high interfacial stress, and poor properties. A novel post-bonded process strategy, slight deformation in the direction of stress parallel to the bonding interface, was developed in the post-bonded treatment of the TiAl/Ti2AlNb joint. The effect of post-bonded processes on the interfacial microstructure, element diffusion, fracture characteristics and mechanical properties were systematically investigated. The results showed that the post-bonded hot deformation (PBHD), compared to the traditional post-bonded heat treatment (PBHT), can effectively increase the major elements diffuse and the growth of the reaction layer, as well as promote the precipitates which distribute uniformly in the reaction layer, finally resulting in superior tensile strength. Compared with the DB samples, the ultimate tensile strength of the PBHD joint increased by 45.58%. In addition, the fracture behavior was further analyzed based on the microfracture morphology and crack propagation path. These findings will facilitate the development of advanced manufacturing processes of blisk for high-temperature light alloys.

Study on microstructures, properties and mechanisms of sinter-joining refractory metal W[sbnd]30Si powders and sputtering targets by spark plasma sintering technique

The development of semiconductor integrated circuits has been limited by the low utilization rate of refractory metal sputtering targets. Spark plasma sintering (SPS) technology has shown great superiority in the sintering and joining of materials, which can be applied to the repair of waste targets and improve the utilization rate. In this study, SPS technology was used to sinter-join the high-purity refractory metal W30Si sputtering powder and the target for integrated circuits to determine the optimal repair process and repair mechanism. The morphological characteristics, grain size, relative density, and Vickers hardness of the repair layer (powder-sintered body) and the target under different joining times were analyzed, and the interface structure and properties of the W30Si joint were also studied. It was found that the W30Si joint was composed of WSi2 and Si phases. The grain size, relative density, and Vickers hardness of the W30Si powder-sintered body and targets increased with the joining time. When the joining time was 10 min (1200 °C), the W30Si joint formed a “zigzag” joining interface, and the bending strength, relative density, grain size, Vickers hardness, and thermal conductivity of the joint were similar to those of the pristine target. In addition, the physical model of SPS sintered and joined refractory metal powders and targets was constructed. Studies have shown that the sinter-joining consists of three stages: early stage, middle stage, and late stage. Among them, the middle stage included two steps that may occur simultaneously, namely the sintering of refractory metal powders and the joining of refractory metal powders with the target, involving pressure welding, micro-arc welding, resistance welding, and diffusion welding mechanisms. This work can provide theoretical guidance for the optimal design of the SPS repair process for refractory metal W30Si sputtering targets.

The Effect of CuO on the Thermal Behavior and Combustion Features of Pyrotechnic Compositions with AN/MgAl

Ammonium nitrate (AN) is of considerable interest to researchers in developing new types of energetic mixtures due to the release of environmentally benign gaseous products during burning and thermal decomposition. However, poor ignition and a low burning rate require special additives to speed up this process. The advantage of this research is the use of high-energy aluminum-based alloys as fuel to compensate for the disadvantages of AN. In addition, the effect of copper oxide (CuO) on the burning kinetics and thermodynamics of the energetic mixture based on ammonium nitrate–magnesium–aluminum alloys (AN/MgAl) is investigated. Alloys based on aluminum were created through a process of high-temperature diffusion welding, conducted in an environment of argon gas. The structure and thermal characteristics of alloys are determined by X-ray diffraction, scanning electron microscopy, and DTA-TG analyses. It has been found that CuO has significant effects on the thermal decomposition of an AN/MgAl-based energetic mixture by shifting the decomposition temperature from 269.33 °C to 261.34 °C and decreasing the activation energy from 91.41 kJ mol−1 to 89.26 kJ mol−1. Adding CuO reduced the pressure deflagration limit from 2 MPa to 1 MPa, and the linear burning rate of the AN/MgAl energetic mixture increased approximately twice (rb = 6.17 mm/s vs. rb = 15.44 mm/s, at a chamber pressure of P0 = 5 MPa).

Study on the Preparation and Properties of a Co-Based Barrier Layer by Diffusion Welding

Study on the Preparation and Properties of a Co-Based Barrier Layer by Diffusion Welding

Development of a Diffusion Bonding Route for Joining Oxide-Dispersion-Strengthened (ODS) Steels for Nuclear Applications

Oxide-dispersion-strengthened (ODS) steels are candidate materials for components in current and future nuclear power plants. One of the issues with using ODS steels is the difficulty of joining them without loss of mechanical performance. In this study, austenitic ODS 316L stainless steel was diffusion-bonded to Inconel 718 superalloy. Having optimized the bonding conditions, a number of samples were made at 1200 °C with a bonding time of 1 hour and pressure of 10 MPa. Preliminary mechanical and microstructural analyses indicated the formation of a sound joint interface, despite slight grain growth in the ODS 316L. A post-bonding thermo-mechanical treatment (TMT) was conducted to refine and restore the microstructure of the ODS 316L. Comparative TEM investigations of the parent ODS alloy and the bonded samples (with and without TMT) along with statistical analyses showed that the Y–Ti–O oxide size distribution remains unaffected by the bonding and complementary TMT cycles, indicating stability of such particles even at very high temperatures and suitability of the devised route for joining the ODS 316L steel.

Evaluation of the sorption/desorption processes of pesticides in biodegradable mulch films used in agriculture

Microplastics from mulch films can be a source of chemical contamination to agricultural soils. In this context, biodegradable films have been widely positioned as a greener choice. However, their sorption/desorption capabilities, in contrast to the conventional plastic types remain understudied. It is for this reason that objective evaluation of their interactions with residual agricultural contaminants becomes important. Our findings reveal that polyethylene (PE) mulch films retained lower amounts of pesticide residues and demonstrated a higher desorption/release [median desorption = 71.86 μg/L or about 50%], while polybutylene adipate terephthalate (PBAT) mulch films retained higher amounts of pesticide residues onto their surface and demonstrated a much lower desorption [median desorption = 24.27 μg/L or about 17%] after a spraying event. A higher ambient temperature had no significant effect on final desorption amounts in both PE [median = 65.27 μg/L at 20 °C and 74.23 μg/L at 40 °C] and PBAT [median = 24.26 μg/L at 20 °C and 24.78 μg/L at 40 °C] mulch films. However, it did favour a faster desorption pace in PE films. Desorption in PBAT and PE plastic types was correlated with the log Kow value [Spearman's correlation: 0.857 and 0.837 respectively, p < 0.05]. However, only a moderate correlation with pKa was observed in PBAT [Spearman's correlation: 0.478, p < 0.05], while none for PE plastic type. Sorption of pesticides onto biodegradable PBAT microplastics were best explained by Elovich [R2: 0.937–0.959] and pseudo-second order kinetics [R2: 0.942–0.987], suggesting the presence of chemisorption. Furthermore, Weber Morris plots suggested the presence of a multi-step process and Boyd plots indicated that film diffusion or chemical bond formation was the rate-limiting step governing this phenomenon.

Laser heat treatment of steels and alloys before diffusion welding

Laser heat treatment of steels and alloys before diffusion welding

The influence of holding time on the microstructure and properties of TLP joints of Q355 steel

Using BNi as the interlayer material, transient liquid phase diffusion welding experiments were conducted on Q355 steel at a welding temperature of 1050 °C under different holding times (10, 15, 20, 25 min). The welded joint microstructure, element diffusion migration, and phase composition were analyzed by using modern analytical testing instruments such as optical microscope (OM), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The mechanical properties of the joint were tested and analyzed by using a microhardness tester, universal testing machine, and impact testing machine. The electrochemical corrosion property of the welded joint was analyzed and studied by using an electrochemical workstation. The results showed that under the conditions of 1050 °C and 6 MPa pressure, the Q355 steel TLP welded joint with better property could be obtained with a 20-min holding time. With the increase of holding time, the width of the bonding interface layer increased first and then decreased, and the microstructure tended to be more uniform. The shear strength gradually increased, reaching a maximum of 496.7 MPa (25 min), but the impact toughness increased first and then decreased, with a maximum of 250.61 J/cm2 (20 min). The corrosion resistance of the joint also improved first and then weakened.

Simple but Effective Heat Treatment on Hot Isostatic Press Diffusion Bonded Ni60A Hardfacing Layer

Simple but Effective Heat Treatment on Hot Isostatic Press Diffusion Bonded Ni60A Hardfacing Layer