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Compound field–assisted laser cladding is an advanced laser processing technology. In this paper, the influence mechanism of single physical field parameters of electromagnetic-ultrasonic compound field–assisted laser cladding on the cladding layer as well as the parameter optimization of compound field–assisted laser cladding are investigated. The Box-Behnken design response surface methodology method is used for experimental design. Through the response surface modeling analysis, it is found that the ultrasonic power has the greatest influence on the microhardness of the cladding layer. For the wear volume of the cladding layer, as the ultrasonic power increases, the wear volume increases and the wear resistance of the cladding layer decreases. Besides, a smaller ultrasonic power and a larger DC current value can obtain a cladding layer with a smaller wear volume. The optimal combination of physical field parameters was obtained through response surface methodology parameter analysis and experimental verification.

The hot cracking susceptibility in the Trans-Varestraint test was evaluated using the nominal strain calculated using the curvature radius of a bending block and the thickness of a specimen based on the theory of material mechanics. The nominal strain was calculated using the material properties at room temperature. Thus, in the Trans-Varestraint test, the non-uniformity of the strain around the weld part due to the temperature distribution is not considered. Therefore, the strain in the Trans-Varestraint test cannot be evaluated correctly. The aim of this study is to reveal the loaded strain at the weld metal to understand the evaluation of hot cracking susceptibility in the Trans-Varestraint test. The loaded strain around the trailing edge of the weld pool of pure iron was measured in-situ using a high-speed camera and high-resolution optical lens. The results of strains measured using image analysis and the finite-element method at the center of the weld bead were compared. Accordingly, it was clarified that the strain was concentrated on the weld part owing to the bending occurring along the weld line, and the strain exceeding the nominal strain was loaded to the trailing edge of the weld pool.

Significant cost and time savings may be realised if multiple weld repairs are undertaken at the same location during the long-term maintenance of naval vessels. Consequently, this investigation simulates full-thickness hull welds, which are required to facilitate the removal and subsequent replacement of hull sections, by assessing the effects of 4 reoccurring weld repairs on a propriety quenched and tempered steel used for naval applications. Optical metallography, electron backscattering diffraction (EBSD), hardness maps, Charpy impact, and dynamic tear tests were conducted. A combination of real weld repairs and Gleeble heat-affected zone (HAZ) simulations were undertaken to characterise the effects of repeated thermal cycles on the microstructure and toughness of different sub-HAZ regions. When the intercritical reheat temperature was just above the AC1 lower critical transformation temperature, the impact toughness was substantially reduced. This includes the fine-grained HAZ where high toughness is typically expected. The low toughness was attributed to the promotion of fracture initiation via debonding between the matrix and second phase which formed at prior austenite grain boundaries. Compared to the original toughness, the application of multiple repeat welds or multiple simulations of the same sub-HAZ thermal cycle did not deteriorate toughness nor noticeably alter the final microstructure.

The laser-MAG hybrid welding in horizontal-vertical (PC) position was used to study the effect of different groove types on the quality of a root weld. Six combinations of bevel angles (50° + 0° (represents the groove angle of upper plate and lower plate respectively), 45° + 5°, 40° + 10°, 35° + 15°, 30° + 20°, and 25° + 25°) and root face sizes of 2 to 4 mm were designed. Hannover analyzer was used to collect electrical signals to analyze the stability of the horizontal-vertical position welding process. The results show that different combinations of groove angle have achieved one-sided welding with root formation. The groove angle has an obvious effect on the weld inclination and molten weld metal flowing down. The combination of bevel angles in which that of the lower plate is smaller than that of the upper plate was more conducive to avoid welding defects such as weld inclination and molten weld metal flowing down. The best groove angle combination was 30° + 20°, which allowed one-sided welding with root formation using a 4-mm root face.

In this paper, dissimilar joining of NbSS/Nb5Si3 composites to GH5188 Co-based superalloy was performed by using two commercial Ni-based brazing filler alloys, BNi-2 and BNi-5 fillers. The interfacial microstructures of the brazed joints were investigated by scanning electron microscope equipped with an X-ray energy dispersive spectrometer. Three-point bending test was also conducted. When brazed with BNi-2 filler alloy at 1020°C for 15 min, typical reaction products across the brazing seam could be identified as NiSS, borides, Ni3Si+Nb3Si, and (Nb,Ti)2Ni phase. Due to the physical and chemical mismatch between the dissimilar base materials, some cracks were observable at the NbSS/Nb5Si3 composites side. The joint strength was only 60 MPa. While brazed with BNi-5 filler alloy at 1160°C for 15 min, the interfacial reaction became more sufficient, and the joints exhibited an average bending strength of 272 MPa.

This study aims to evaluate the weldability of dissimilar welds with the Inconel 625 and the Hastelloy C-276 nickel-based alloys deposited on ASTM A36 and AISI 1045 carbon steel plates. The welds were carried out by the GMAW process and evaluated by the Trans-Varestraint test. The test results were statistically evaluated, and Fusion Zone solidification processes were simulated in JMatPro software using several dilution levels. The analysis of variance (ANOVA) test results showed that the two different base metals did not affect the weldability of Inconel 625. However, the Hastelloy C-276 alloy showed a significant drop in weldability with the AISI 1045 steel compared to the ASTM A36. The results of the Hastelloy C-276 as the filler metal and the AISI 1045 steel as the base metal showed greater susceptibility to solidification cracking than all the other pairs tested, according to the Trans-Varestraint test. Moreover, the ANOVA test results indicated that the different heat input levels did not influence the sets’ weldability; this was probably because there was only a tiny variation in the dilution levels. The solidification process simulation indicates that higher dilution levels promote the precipitation of a larger secondary phase fraction.

Modern products and structures require efficient material joining processes for their construction, able to combine similar or dissimilar materials, which almost always includes high-performance polymers. To design such joints, it is necessary to first understand the techniques currently used in this technological field and how they can be improved using advanced technological joining processes. In this manuscript, a review of several polymer-joining techniques is made, highlighting the recent technological advances in this field. The search for improved mechanical performance and lower costs has led to the development of new, high-performance engineering polymers, which require highly specific joining processes. These can include adhesive bonding, mechanical joining, welding or a combination of different processes, a technique known as hybrid joining. Several experimental works available in the literature have proven the validity of these techniques, although optimization processes are necessary to attain maximum performance. Additionally, extensive numerical with different methods and models has been carried out to better understand the processes and support parametric analysis. The intent of this work is to review studies on the most important polymer bonding techniques, the numerical models applied to simulate these techniques, the use of hybrid joints and describe promising techniques that are being developed and proposed for future use.

Active vision sensing is widely used in intelligent robotic welding for bead detection and tracking. Disturbed by welding noise such as arc light and spatter, it is a hard work to extract the laser stripe and feature values. This paper presents a method for denoising and feature extraction of weld seam profiles with strong welding noise in gas metal arc welding (GMAW) process by using stacked denoising autoencoder (SDAE). This algorithm encodes the images of various butt joints with strong welding noise to several useful intermediate representations, which can be decoded to the image of pure laser stripe in 1-pixel width. The results show little deviations when there are large spatters across the laser stripe. A back propagation neural network (BPNN) is developed to verify the reliability of the intermediate representations gotten from the encoder, in which the intermediate representations are input neurons and the weld seam width is output neuron. The average width error in training dataset and testing dataset is 0.042 mm and 0.061 mm. The results show that this algorithm can extract the weld seam profiles with strong welding noise and extract feature values accurately.

High-energy density beam processes for welding, including laser beam welding and electron beam welding, are essential processes in many industries and provide unique characteristics that are not available with other processes used for welding. More recently, these high-energy density beams have been used to great advantage for additive manufacturing. This review of the literature serves to provide an overview of the evolution of the laser and electron beam processes including the fundamental nature of the beam itself and how such a high-energy density beam has been applied for welding. The unique nature of each process regarding weld bead formation and penetration, and metallurgical considerations are covered in detail. In addition, the evolution of monitoring systems for both characterization and control of these beam processes is reviewed. Over 500 references have been cited in this comprehensive review that will allow the reader to both understand the current state-of-the-art and explore in more detail the fundamental concepts and practical applications of these processes.

The joining of the SiCf/SiBCN composite was difficult due to the undue reactions between the SiCf/SiBCN composite and the common Ni- or Co-based filler alloy. In this paper, a new filler alloy with the nominal composition of Co-20Ni-12Pd-18Nb-15Cr (wt.%) was newly designed to join the SiCf/SiBCN composite. Compared with the BNi-5 filler alloy, the periodic banded structure in the reaction layer was eliminated. During the brazing process, the element Cr played an active role in the interfacial reactions and formed Cr23C6 layer at the surface of the SiCf/SiBCN composite. The interfacial reaction layer could inhabit the diffusion of the elements Co and Ni to the SiCf/SiBCN substrate. And then the interfacial reactions were controlled well. Under the brazing condition of 1200 °C/10 min, the average joint strength was increased from 18.2 to 54.9 MPa.

Friction stir welding (FSW) is a relatively new welding technology. Although FSW technology has been widely used in many industries, there is a lack of effective online detection method of process parameters. Weld temperature and tool positioning are two key parameters in the study of process parameters. To realize online measurement of weld temperature and tool positioning in FSW, a measurement method of weld temperature and tool positioning is proposed by designing a new online detection device in FSW. The weld temperature measurement is realized by the material emissivity model based on the principle of infrared temperature measurement. Based on the principle of trigonometric distance measurement, the tool positioning is measured by data processing algorithm. In order to verify the feasibility of the measurement method, the welding processes of aluminum alloy with two thicknesses are detected online. The results show that the weld temperature measurement accuracy of the online detection device is within ± 2%. The measurement of tool positioning is realized. This measurement method proposed in this paper can be applied to the optimization of process design and temperature feedback control.

The formations and fracture behavior of the AA2A14-T6 aluminum alloy friction stir welded (FSWed) joints are investigated under different ratios of rotational speed to welding speed (n/v). The relationship between the viscous layer (δ) and the rheological layer (ξ) is the key factor to determine the welding quality of joints. When δ

Friction stir welding (FSW) is a solid-phase welding method. Weld forming and welding quality are related to the heat generated by plastic flow in FSW process. Therefore, it is of great significance to realize the measurement of the viscoplastic heat generated in FSW process. In this paper, based on the working principle of rotary viscometer, the calculation model for the viscoplastic heat in friction stir welding was proposed. The validity of the calculation model was verified by simulation experiment. The correctness of the calculation model was verified by friction stir welding experiment.

Dissimilar metal welds (DMWs) made between ferritic steels and austenitic alloys are used extensively in high-temperature power plant components. These DMWs experience premature creep failure in the ferritic steel’s heat affected zone (HAZ), close to the weld interface. Steep variations in microstructure and chemical composition across the dissimilar weld interface have been the contributing factors for the failure. Graded transition joints (GTJs), developed by functionally grading the chemical composition in layers, have been proposed as potential candidates to replace DMWs. In this research, GTJ coupons were fabricated between 2.25Cr-1Mo steel and Alloy 800H base material using two filler materials: (i) Inconel 82 and (ii) P87. These samples were aged at 600°C for 2000h to accelerate high-temperature microstructural evolution seen in service conditions, before subjecting them to short-term (~1 month) creep tests. Surface strains were measured using digital image correlation (DIC) technique to extract creep strain rates at different locations within GTJs. Both the GTJs exhibited heterogeneous creep strain distribution. Creep strain accumulated in the FGHAZ of 2.25Cr-1Mo steel, similar to type IV failure associated with Cr-Mo steel weldments. Microstructure based creep model framework was developed to describe the discrete creep strain rates observed in various 2.25Cr-1Mo steel regions of GTJs.

The optimization of welding parameters of the welded joints of TC4 titanium alloys/304 stainless steel (TC4/304 SS) by friction stir lap welding (FSLW) based on orthogonal test was researched. The results show that under low heat input (low rotating speed and high traversing speed), there was a damaging defect in stir zone (SZ) and cracks started from the defect under the tension. Under high heat input (high rotating speed and low traversing speed), the intermetallic compounds were barely formed, and the cracks formed from 304 SS blocks existed in thermal mechanically affected zone of TC4 titanium alloys (TMAZTC4), eventually obtaining the highest fracturing load. However, under middle heat input (middle rotating speed and low traversing speed), the intermetallic compounds and the maximum hardness were found at the interface, and cracks started from these compounds under the tension, getting a middle fracture load. In conclusion, the joints with good properties can be obtained with high rotating speed and low traversing speed.

Transient liquid phase (TLP) bonding of Ti-6Al-4V/IN718 dissimilar joint was investigated using Cu interlayer at 950 °C for 5–45 min. The microstructure of the bonding zone was studied by using optical and scanning electron microscopes, energy dispersive spectroscopy, and X-ray diffraction analysis. Shear and microhardness tests were also used to evaluate the mechanical properties of the TLP joints. The results indicated that α-Ti, Ti2Cu, and Ti2Ni phases were formed in the athermally solidified zone of the joints. A Widmanstatten structure consisting of eutectoid mixture of α-Ti and Ti2Cu was formed in the diffusion affected zone of Ti-6Al-4V side, and the formation of β(Nb) and NiTi eutectic and Cr2Ti, FeTi, Ni3Nb, Fe5Nb3, and Cu0.035 Ni0.565Ti0.4 intermetallic compounds was predicted in the diffusion affected zone of IN718 side. The hardness values decreased in different bonding zones with extending the bonding time, while an inverse trend was observed in the athermally solidified zone. The maximum shear strength of 367 MPa was obtained. The morphology of the fracture surfaces of shear samples was investigated.

The morphology of the weld seam, the formation mechanism of interface, and the microstructure and mechanical properties of both direct and AlSi12 (ER4047)-added dissimilar 5A06Al/Ti6Al4V lap joints were investigated, respectively. The Gibbs free energies of intermetallic compounds, such as TiAl3, TiAl, and Ti3Al, were calculated. The results showed that the interface layers were mainly composed of Ti3Al, TiAl, and TiAl3, and the order of them was TiAl3, TiAl, and Ti3Al from outside to inside. The addition of ER4047 interlayer could suppress the formation of IMCs and reduce the micro-cracks in TiAl3 layer. The ER4047-added joints featured good mechanical properties, i.e., the shear strength of 2087 N, 2405 N, and 2157 N respectively, which were much higher than the shear strength of 1721 N for the direct joint. Furthermore, the fracture model of the direct joint was brittle fracture, while that of the ER4047-added joints was quasi-cleavage. The results can provide theoretical guidance for the prediction of Ti/Al interface reaction and welding of other dissimilar metals.

Carbon steels can be sensitive to solidification cracking. Predicting their susceptibility to solidification cracking can save cost and time compared to testing, and it can be very useful for designing new steels or welds. Crack susceptibility predictions were made for carbon steels using the recently proposed simple susceptibility index for cracking during solidification, maximum │dT/d(fS)1/2│ near the end of solidification (T temperature and fs fraction solid). T vs. (fS)1/2 curves of the carbon steels were calculated by three different solidification models: equilibrium, Scheil, and Scheil with back diffusion of the available commercial thermodynamic software. The crack susceptibility predictions based on these solidification models were compared to various crack susceptibility test results of carbon steels, and the predictions based on Scheil with back diffusion were found consistent with the most of the crack susceptibility test results. Solidification temperature ranges of the carbon steels, determined based on the solidification models of equilibrium, Scheil, and Scheil with back diffusion, were used to explain the crack susceptibility predictions. The role of the alloying elements of the carbon steels in solidification cracking susceptibility was discussed.

In this study, we develop a 3D transient mathematic model to simulate the heat transfer, fluid flow, and geometry morphology in GMAW-based wire arc additive manufacturing (WAAM). The processes of droplet formation, growth, and detachment from the end of wire electrode, who travels dynamically along the scanning direction, are coupled with molten pool for the first time by considering their own mechanical conditions and solving the transport equations in the whole solution domain. By the developed model, the simulations of single-pass multi-layer of WAAM of Al-5%Mg are performed. The calculated results indicate that when the droplet falls into the molten pool, the maximum velocity inside the droplet reaches 0.9m/s, resulting in that liquid metal in the middle flows toward the bottom of the molten pool and a depressed region is formed. On the surface of molten pool, the liquid metal dominated by Marangoni force flows from center to periphery, and on the bottom of molten pool, a clockwise circulation is formed. In addition, the interlayer idle time contributes to the formation of deposit with higher height and narrow width. Finally, to validate the model, the deposit profiles are also compared between simulated and experimental results.

MARBN alloys, which are anticipated an estimated 25 °C increase in advanced ultra-super critical (A-USC) power plant operating temperature, are expected to be commercially available soon and will partially displace some older materials and lead the market. Two examples are the Japanese alloy, 9Cr-3W-3Co-Nd-B material, which is considered a strong contender in wrought pipework, and the UK’s IBN-1 alloy which currently leads the development in cast steels. Through the courses of two consecutive UK collaborative projects IMPEL and IMPULSE, a matching composition filler metal for welding MARBN alloys in the form of shielded metal arc SMAW electrode has been developed. The design of this filler metal was aimed to optimize the deposit chemical composition hence to provide creep resistance properties matching the base alloys. The weld metal was specifically intended for high integrity structural service at expected temperatures. Accordingly, the minor alloy additions responsible for its creep properties were kept at the middle of the base alloys or at least above the minimum considered necessary to ensure a satisfactory performance. This paper introduces the design, investigation and test results of the matching filler metal. Findings relevant to the microstructure, mechanical properties at ambient and elevated temperatures, including creep properties of the all-weld metal and weld joint made with IBN-1 base alloy, are presented.

The purpose of this paper is to present the extension of a previously developed strain-based fracture mechanics (SBFM) model from one to two dimensions for simulating fatigue crack growth in steel arc welds. The one-dimensional (1D) SBFM model is first briefly reviewed. Steps for extending it to simulate 2D growth of a semi-elliptical surface crack in a weld are then described. An application of the new model is lastly presented, which consists of analysing the behaviour of structural steel weld specimens from a previously published fatigue test program, in which the fatigue performance of weld specimens was enhanced by high frequency mechanical impact (HFMI) treatment. In this application, the effect of the treatment-induced compressive residual stress on the crack shape is simulated, and it is shown how the extended 2D SBFM model can be used to establish probabilistic design stress-life (S-N) curves for various loading conditions.

ISO 12135, which provides a fracture toughness test procedure, requires crack front straightness. In order to meet this requirement in weld specimens, Annex C to ISO 15653 provides a local compression (LC) technique. Although this technique has been used widely, some interested parties have reported that it often results in excessive underestimation of the critical CTOD. Following these previous studies, the authors reviewed the appropriate LC conditions and presented the typical effects of LC on fracture toughness and crack front straightness in this paper. In this regard, we conducted numerical analysis, sacrificial test, and fracture toughness test and investigated the LC effect on the crack front straightness and fracture toughness. In conclusion, a typical LC with an appropriate platen results in a straight crack front, but also has a large influence on fracture toughness, and it is difficult to solve this problem only by adjusting the amount of LC strain.

Ultrasonic vibration-assisted plasma arc welding with controlled pulse current waveform was developed to weld the 8 mm thick stainless steel plates. Both bead-on-plate and butt welding experiments were carried out with open-loop and closed-loop control strategies under different welding conditions. The signals of welding current and efflux plasma voltage and the images of keyhole exit were sensed to monitor the keyhole status during the welding process. It was found that the ultrasonic vibration-assisted plasma arc can completely penetrate the stainless steel plates with the thickness of 8 mm in a single pass with higher welding speed or lower peak welding current in controlled pulse keyhole mode. By continuous real-time adjustment of welding current waveform in closed-loop strategy, the “one-pulse-one-open keyhole” mode was achieved successfully with lower welding heat input. Due to the reduction of heat input and further constriction of plasma arc under the action of ultrasonic vibration, the weld was narrowed and the depth-width ratio was raised.

That increasing temperature is beneficial for solder-wetting but not for amorphous-maintaining the state causes difficulties in joining of Zr-based bulk metallic glass (BMG). In order to solve the contradiction, this paper presents a two-step process of pre-cladding ultrasonic soldering, in which a Zn-6Al-3Cu-20Sn solder layer was firstly vacuum-cladded on surface of a Ti-6Al-4V sample, and then a Zr-14Cu-10Ti-8Ni BMG sample was ultrasonic-soldered to the solder layer without flux. Microstructures of the Zr-14Cu-10Ti-8Ni/Zn-6Al-3Cu-20Sn/Ti-6Al-4V soldering joints were studied using optical microscope, SEM, EDS, and XRD, and shear strengths were tested. Results show that shear strength ranges from 20 to 50 MPa among the joints obtained under different soldering temperatures and ultrasonic times. Shear fracture of all the experimental ultrasonic soldered joints occurred at the interface between solder and Zr-based BMG. The fracture surface shows a mixture of solder tearing and solder peeling off from the surface of the Zr-based BMG. Pits or grooves formed on surface of Zr-based BMG by ultrasonic cavitation benefit not only chemical adhesion but also mechanical adhesion by an anchoring effect. This work confirmed that ultrasonic treatment is very effective for the soldered joint of Zr-based BMG.

Powder bed fusion (PBF) is an additive manufacturing (AM) technique commonly used to manufacture metallic components. External geometry of parts printed by PBF process can be extended by regular processes, namely, laser cladding and spraying powder metal. But these methods have disadvantages such as increased heat-affected zone (HAZ) and extended deficiencies like cracks and pores, whereas samples produced with directed energy deposition (DED) exhibited strong metallurgical bonding and has reduced HAZ due to least dilution. The present work investigates the properties of stainless steel 316L (SS316L) sandwich structure built by combining PBF and DED process. The external geometry of the SS316L samples built by PBF was extended by using DED technique. Metallurgical and mechanical characteristics of DED extended PBF samples were studied. Tensile properties such as percentage elongation and tensile strength were compared for PBF, DED, and SWS (DED extended PBF). It was found that the yield stress for the DED samples, PBF samples, and SWS samples is in the range of 486 MPa, 564 MPa, and 401 MPa. Moreover, the average hardness of the interface portion is found to be 220.5 HV and it is higher than the hardness observed in the PBF and DED regions.

The empirical equation to predict the heat-affected zone (HAZ) hardness of B-added steels has been proposed. For this purpose, weld thermal cycle simulation tests of both B-free and B-added steels in combination with hardness measurements were conducted. Firstly the previous HAZ hardness prediction equation was modified using the experimental results of B-free steels. Next, by introducing the B effect on hardenability to the modified equation, a new empirical equation to predict HAZ hardness of B-added steels was developed. The present equation takes into account the effects of peak temperature and Mo composition on B hardenability. The comparison of the predictions with the experiments of the weld thermal cycle simulation tests showed that the present equation can predict the HAZ hardness fairly well. The adjustable parameters of the B effect on hardenability introduced to the equation agree with the conventional results in the literature. To confirm that the present equation can be used to predict HAZ hardness of actual welded joints, hardness profile of welded joints was measured. The predicted HAZ hardness profile has shown to be in good accordance with the measured hardness profile.

Refill friction stir spot welding (refill FSSW) is one of the most industrially promising friction stir spot welding variants. The absence of an exit hole improves the effectiveness of surface treatments and minimizes damage by fouling. Aerospace aluminium alloys AA2024-T3 and AA7075-T6 with a thickness of 2 mm were used in this investigation. A range of values for rotation speed and plunge depth were experimented to determine the most promising process parameter combination based on the cross-sectional analysis and lap shear strength. The effect of an interfacial sealant on the weld properties was determined for both alloys using the most promising process parameter combination. Fatigue life analysis and fractography using scanning electron microscopy were performed for specimens with and without sealant.

The joining of plastics is required because component geometries are severely restricted in conventional manufacturing processes such as injection molding or extrusion. In addition to established processes such as hot plate welding, infrared welding, or vibration welding, hot gas butt welding is becoming more and more important industrially due to its advantages. The main benefits are the contactless heating process, the suitability for glass fiber reinforced, and high-temperature plastics as well as complex component geometries. However, various degradation phenomena can occur during the heating process used for economic reasons, due to the presence of oxygen in the air and to the high gas temperatures. In addition, the current patent situation suggests that welding with an oxidizing gas is not permissible depending on the material. On the other hand, however, there is experience from extrusion welding, with which long-term resistant weld seams can be produced using air. Investigations have shown that the same weld seam properties can be achieved with polypropylene using either air or nitrogen as the process gas. Experimental investigations have now been carried out on the suitability of different gases with regard to the weld seam quality when welding polyamides, which are generally regarded as more prone to oxidation. The results show that weld strengths are higher when nitrogen is used as process gas. However, equal weld strengths can be achieved with air and nitrogen when the material contains heat stabilizers.

Additive manufacturing (AM) using PBF (powder bed fusion) is widely applied in industry with many advantages but also some drawbacks such as productivity rates and limited dimensions. Future implementations of AM will require a re-design of components in order to reserve AM for the particular complex geometries, to join AM subassemblies or to connect with conventional components. It brings the aspect of weldability of AM parts in the picture. This study is investigating the weldability of AM 316L components using common welding processes such as manual GTAW. Bead-on-plate tests were started as a first step to examine weldability. After satisfactory results, two AM pipe components were fabricated (PBF) in the same built to be welded to conventional 316L parts. One AM pipe component was used to characterize the mechanical properties while the other test coupon was welded to conventional pipe by manual GTAW. The test welds were submitted to a mechanical and corrosion testing program including creep rupture testing. It was decided to start the weldability analysis in the worst condition, i.e., As Build/As Welded (AB/AW) without any heat treatment nor post-processing. Based upon the results obtained for the conditions tested, it could be concluded that AM (PBF) components are weldable.

In this work, the industrial X-ray computed tomography was exploited for measuring maximum crack depths across the weld interfaces within resistance spot welding (RSW) specimens welded under intensive welding condition. Individual crack profiles were measured for each sample and presented in terms of the total crack length, the maximum crack depth and the median crack width. A linear trend between maximum crack depth and median crack width was observed, where the associated coefficient of determination was sufficiently high (R2 = 0.79). Hence, the crack width is proposed to predict the crack depth. Based on the experimental findings, the effectiveness of the proposed method is demonstrated through machine learning studies, and a simple relation to predict the internal crack depth from the surface crack width was further developed. Semantic segmentation results proposed an algorithm succeeded in separating enough crack areas to calculate the crack width. Since Zn-assisted liquid metal embrittlement (LME) is now accepted as an inevitable consequence with respect to RSW process, the methodology demonstrated in this work can potentially offer the insights into an effective and automatic method of quantifying LME cracks.

This study aimed to investigate the heat-affected zone (HAZ) behavior in an API 5L X70 steel welded by the gas metal arc welding process (GMAW). In the steel welding processes, this region is very critical due to microstructural and allotropic transformations that affect the mechanical properties. Three samples were welded using a robotic arm with different welding speeds, thus obtaining three different heat inputs, which were 2.0 kJ/mm, 2.5 kJ/mm, and 3.0 kJ/mm. For all heat inputs, the microstructures of the HAZ showed the Widmanstatten ferrite, Acicular ferrite, bainite, and martensite and retained austenite, which influenced the mechanical properties of this region. The electron backscattering diffraction analysis showed that the presence of low-angle grain boundaries (2–15°) increases the fracture toughness. The kernel average misorientation map and the results of the Charpy impact test showed that the heat input of 3.0 kJ/mm lead to characteristics of the HAZ that are remarkably similar to the base metal (BM).

Synergetic double-sided probeless friction stir spot welding is a novel process proposed in this study, which is used to solve the contradiction between the improvement of metallurgical bonding and deterioration of hook defect. The effect of the coordinated movement of the tools on the joint formation was evaluated based on the coupled Eulerian-Lagrangian technique. By flexibly adjusting the welding parameters on both sides, the mechanical interlock caused by hook defect could be effectively regulated while significantly improving the metallurgical bonding, due to the enhancement of thermo-mechanical cycle along the thickness direction. According to the microstructure analysis, the interfacial evolution was ascribed to the combined effects of plastic deformation, material flow, atom diffusion, and recrystallization, as well as local abrasion. In addition, the microhardness profile exhibited a uniform distribution. Based on the above characteristics, the technology is expected to obtain higher strength joints, which will promote its applications in the manufacture fields.

In the present study, the effect of heat input of gas tungsten arc welding on the microstructure and mechanical properties of AZ91 magnesium alloy was investigated. The microstructural studies were performed by using an optical microscope and scanning electron microscope equipped with energy dispersive X-ray spectroscopy, and tensile test was used to evaluate the mechanical properties. It was shown that, comparing to the base metal, a fine microstructure of α(Mg) and Mg17Al12 phase is formed in the weld metal and the size of α(Mg) phase slightly increased with heat input during welding process. The results also indicated that the thickness of partially melted zone increased with heat input. Tensile strength of welded samples was lower than that of the base metal and it decreases with increasing heat input. Failure of the welded specimens accrues in the partially melted zone. Studying of fracture surface revealed that the interface of α(Mg) and Mg17Al12 compound acts as crack initiation and growth path during the tensile test. Formation of cleavage steps in the fracture surface was the dominant fracture mechanism during tensile tests.

In the present work, an Al-Cu-Si-Ni-Mg brazing filler metal was developed for the joining of 6063 aluminum alloy and graphite metallized with Ag-Cu-Ti paste. The joint microstructures were studied by means of SEM and EDS. Results show that joints with a good quality can be produced at a brazing temperature of 550 °C for 10 min. TiC was formed at the graphite/active Ag-Cu-Ti paste interface due to the reaction between Ti and C, and thus, the wettability on the graphite was improved. Compared to the metallization stage, more diffusions of Al, Ag, Ti, and Cu from interlayer to graphite are observed. The bonding area mainly consists of α-Al, Ag rich phase, α + Al2Cu + Si, Al2Cu, and TiC. It is shown that joints with good quality can be produced and the average shear strength of the joints is 21 MPa.

In this study, Ti5Si3/Ti3Al composite was successfully vacuum-brazed with Ti-33Zr-16Cu-13Ni (wt.%) filler alloy. The typical interfacial microstructure of the joints presented a symmetrical characteristic, which mainly consisted of Ti3Al, Ti2Ni, and α-Ti phases. The effects of brazing temperature and holding time on the interfacial microstructure and mechanical properties of the joints were investigated in details. The optimized average shear strength of 224 MPa was obtained when brazing at 900 °C for 5 min. The high temperature shear strength of the joints reached 377 and 405 MPa at 600 and 650 °C, respectively. In addition, the microstructure evolution mechanism of the joints was put forward based on the experimental analysis.

The twin-wire CMT with Al-Si filler was used as weld/brazing process for dissimilar joining of stainless steel and aluminum. It is shown that this approach can ensure a satisfactory performance of the joint and the dissimilar joint exhibits typical characteristics of common known steel/aluminum weld brazing joints. Intermetallic compounds (IMCs) were detected next to the steel as a layer of Fe2Al5, as a layer of Fe3Al2Si4 adjacent to the aluminum side and as a scattered phase of Fe4Al13 in between. The total thickness of the IMCs was determined with 2–4 μm. The maximum tensile strength of the weld joints without reinforcement was up to 96 MPa and cross tensile test specimens fractured at the brazing interface at about 35% of the strength of the aluminum. An increase of the wire feeding rate and decrease of the welding speed thereby outperform beneficial in respect to wetting characteristics. However, excessive heat input (e.g., wire feeding rate larger than 7.5 m/min) causes a reduction of the mechanical properties. A groove gap about 1 mm ensures furthermore a good back appearance.

Gas protection is very important in arc welding processes and several factors influence its effectiveness. This paper provides a discussion of the applicability of the Schlieren technique to arc welding processes. Tests were performed with different types of shielding gas and with GMAW and GTAW torches, in order to highlight differences associated with the various conditions. The results obtained in conjunction with a review of results reported in the literature allowed an evaluation of the limitations associated with the use of the Schlieren technique in the arc welding processes. The most important limitation is that the visualization is inherently difficult when using pure Ar gas, meaning that in most situations it is not possible to adequately visualize the flow interface with atmospheric air, which is the main region of interest in this type of analysis. However, visualization is possible in regions where pure Ar is heated, or when mixtures with other gases are used. In addition, the results obtained with different sources of light were compared and the test was performed by filming the arc welding or with the gas flowing through the torch without the arc. The differences observed in the results obtained are discussed herein.

This paper discusses the effect of different combinations of preheating and post-heating on the corrosion and hydrogen embrittlement of Grade-91 steel weld joint in the as-welded condition. Though these welds are subjected to post-weld heat treatment (PWHT), there could be long delay in executing this, especially in the case of fabrication of large components, and during this delay, the welds in as-welded conditions are prone to environmental degradations like hydrogen embrittlement and different forms of corrosion. Though recommended minimum preheating and post-heating conditions are already known for welding of this class of steels, marginally increasing the temperature of preheating and post-heating or increasing the duration of post-heating can permit longer delay in the post-weld heat treatment (PWHT), without increasing the risk of environmental degradation. With this objective, a set of thirteen single-V multi-pass gas tungsten arc weld joints of Grade-91 steel fabricated with different preheating and post-heating combinations. Results indicated a significant reduction in residual tensile stresses in the weld metal and reversing into compressive stresses upon preheating and post-heating at 300 °C. Moreover, diffusible hydrogen content and corrosion rate decreased significantly with the preheating and post-heating. However, there are no significant variations in the microstructure, mechanical properties, and hydrogen embrittlement with preheating and post-heating. This study proved that the risk of embrittlement in Grade-91 steel welds due to an indefinite delay in PWHT could be minimized by combined preheating and post-heating.

Made available in DSpace on 2021-06-25T10:24:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-06-01 The aim of the present study is evaluating the feasibility of Oxy Fuel Welding (OFW), using liquefied petroleum gas (LPG), for the joining of the glass fiber/polyetherimide composite and aluminum alloy 2024-T3, which combine the effectiveness of the joint and the low cost of operation. A statistical experimental design was performed to determine by OFW parameters, and the samples were welded and evaluated after Lap Shear Strength (LSS) loading as the planning response variable. For a better result of the joint strength, through the mechanical interlock between the laminate and the AA2024-T3, anodization process was performed. A maximum value of LSS with 6.20 MPa was obtained, with optimized values reaching 6.32 MPa. The results of mechanical resistance of the hybrid junction involving the anodized AA2024-T3 were doubled, being 13.80 MPa in relation to the maximum obtained from the joint without treatment, confirming the increase of the interaction between these two materials. This fact was confirmed by the roughness test and optical microscopy. After welding, the AA2024-T3 structure was converted into a new structure of equiaxed grains, from the recrystallization of the grains, the hardness value being reduced by approximately 24%. From the TGA and EDS analyses, there was no significant difference in the degradation temperature of the thermoplastic composite, confirming the efficacy of the process for hybrid joint AA2024-T3 and GF/PEI composite, and there is no indication of contaminant that could interfere with the quality of the weld. Materials and Technology Department School of Engineering São Paulo State University (UNESP) Technology School of Pindamonhangaba FATEC Materials and Technology Department School of Engineering São Paulo State University (UNESP)

The lightweight construction of steel structures is often limited by the mechanical properties of the weld metal. The strength values of modern base materials are not achieved in the weld metal. There is a considerable need to develop welding consumables that allow the processing of modern fine-grained structural steels without limiting their potential. The Physical Vapor Deposition (PVD) coating of welding wire electrodes can increase the strength of the weld metal of a Mn4Ni2CrMo welding wire electrode by up to 30%. By using different coating elements, the Hall–Petch relationship can be exploited and such an increase in strength can be achieved. Especially by applying titanium, vanadium, and yttrium coatings, the strength of the weld metal can be increased. Due to a multilayer structure of the coating, the weld metal and the process can be influenced independently of each other. The effects of mono-element coatings and multi-component coatings on the weld metal and the process are discussed. PVD coatings allow welding wire electrodes to be individually adapted to the requirements.

This article makes an attempt to investigate the outcome of activated flux and filler wire in addition to A-TIG welding and TIG welding of Inconel 625 respectively. Ni-Cr-Mo enriched filler namely ERNiCrMo-3 was used to join 6.5-mm-thick plates. Microstructure characterization, mechanical properties evaluation and secondary dendritic arm spacing measurements were carried out to find the cause of the perceived differences. Tensile test failures were observed at the weld zone in both welding processes. Charpy impact studies showed that weldment using A-TIG revealed a low toughness value compared to the TIG weldment. Root bend test showed no discontinuity in both fusion zones and hence, the weldment was produced without defect. The deleterious laves phase was reduced when activated flux and fillers were used. Corrosion performance was undertaken in a 3.5 wt% NaCl solution, to illustrate the outstanding corrosion resistance in Inconel 625’s fusion zone using A-TIG and TIG welding processes.

The work presented in this paper deals with the study of the influence of the operating parameters of welding on observables which are the geometrical characteristics of the melted zone. In this study, the method implemented is of the SMAW (Shielded metal arc welding) manual arc type and is used to assemble the pipes through the filling of a V-shaped chamfer between two tubes 1219.5 mm in diameter, 13 mm thick, and a material of grade X70 steel. In order to increase the productivity and reliability of the chamfer filling operation, we used the experimental designs method, on the one hand to estimate the effects of the operating parameters and their interactions on several functions characterizing the morphology of the weld bead, and on the other hand, to provide a mathematical model that links the welding process operating parameters to the objective functions studied.

Available fatigue recommendations are typically developed for arc-welded joints. Some of them may need to be adjusted to fit fatigue life of joints manufactured with non-conventional welding techniques since they show different mechanical properties. Laser beam and friction stir welded butt and overlap joints made from aluminium are addressed in this paper focused on a comparison between different fatigue assessment methods. For an evaluation, S-N data from published papers was collected. Additionally, fatigue tests on laser beam and friction stir welded overlap joints were carried out. For a fatigue assessment, the nominal stress, notch stress and effective stress approach were applied. The comparison of the endurable nominal stresses showed a comparatively high fatigue strength of the tested friction stir welded overlap joints in comparison to literature data. The notches at the interface of the overlap joints were observed to have an asymmetric geometry compared to the common symmetric one, frequently found in literature, leading to a lower stress concentration. A comparison between endurable nominal stresses and the classes FAT 28 for butt welded and FAT 12 for overlap welded joints resulted in a conservative design for the majority of specimens. An evaluation based on notch stresses lead to partly non-conservative results that could be explained by the mild notches present at the laser-beam welded butt joints. For the effective stress approach, an evaluation of the micro-structural length was performed and a FAT-value is proposed.

Insulated copper wire has been widely used in many industries, but the insulating coating must be removed before welding because it will hinder the formation of joints. Therefore, in this work, the resistance thermocompression microwelding process for insulated wire without removing the coating in advance was proposed. Through detailed mechanical testing and metallurgical examination, the effects of welding voltage on the joint appearance, joint macro-/microstructure, joint breaking force, and joint fracture mode were investigated. The results showed that joints were achieved by solid-state bonding. As the welding voltage was further increased, the joint breaking force increased first and then decreased. Corresponding to the change of the welding voltage, the fracture mode of the joints changed from interfacial fracture to partial pullout fracture. The fracture position also moved backwards gradually, which was caused by the expansion of the bonding area, the improvement of the interfacial strength, and the amount of heat input. Finally, an orthogonal experiment was conducted to investigate the significance level of three parameters. Under the optimal for joint breaking force parameters (2.1 V, 24 ms, and 12 N), the average achievable force was 1.1723 N, which was about 83.7% of the breaking force of the as-received wire.

This paper explores the possibility of producing an improved interference-fit tubular joint between pure copper and stainless steel tube by electromagnetic crimping (EMC). Successful joints are obtained with optimal parameters consisting of the outer surface profile of the inner tube and discharge energy. Joints exceeding the strength of the parent tube are formed without any metallic bond formation. Three destructive testings, namely, pull-out, compression and torsion tests, have confirmed the successful joint formation as the failure occurs in the copper base tube. Analysis of failure mechanisms has revealed joint behaviour at various discharge energies and surface profiles. Among smooth, knurled and threaded surface profiles with different discharge energy levels, knurled surface provides best joint strength at 6.2 kJ, which has shown a failure in the parent Cu tube during all three destructive testings. Radial deformation of the tubes is measured and compared for different discharge energy and surface profile. No metallic bond formation and the wavy interface are observed between the joining partners during microstructural analysis. Furthermore, no elemental overlapping is observed during energy dispersive spectroscopy mapping analysis indicating an absence of diffusion. Higher micro-hardness is observed near the Cu-SS tubular joint interface due to strain hardening caused by high-velocity impact.

The present study reports the effect of heat input on the evolution of microstructure, mechanical properties, and corrosion behavior of electron beam butt welded zircaloy-4 sheet. Joints prepared with lower heat input demonstrated lower peak temperature and higher cooling rate that resulted in narrow fusion zone and heat-affected zone. Fine basket weave Widmanstatten type structure in fusion zone was observed at lower heat input, while at higher heat input, a large columnar grain with coarse parallel plate Widmanstatten type structure was observed. Traces of second phase particles Zr(Cr,Fe)2 were also found in the fusion zone. The tensile strength of all welds was better than the base metal, irrespective of heat inputs. However, the joint prepared with lower heat input demonstrated higher ductility compared to other joints. The dominant mechanism of corrosion was found to be pitting type and it was supposed to be caused by intermetallic precipitation. The extent of corrosion decreased with decrease in heat input. Adhesive wear was found to be the dominant mechanism of wear and the coefficient of friction decreased with the decrease in heat input.

A 50.8-mm-deep gas tungsten arc weld was made with matching filler metal in cast Haynes 282 alloy. The narrow-gap joint was filled with 104 weld beads. Visual and dye-penetrant inspection of cross-weld specimens indicated that the cast base metal contained numerous casting defects. No visible indications of physical defects were found in the weld deposit. The weld heat-affected zone was characterized by microcracking and localized recrystallization. The cause of the cracking could not be determined. Hardness testing showed that a softened region in the as-welded heat-affected zone was nearly eliminated by post-weld heat treatment. Tensile testing up to 816 °C showed that cross-weld specimen strengths ranged from 57 to 79% of the cast base metal tensile strength. The stress-rupture strengths of cross-weld specimens are within 20% of base metal reference data. Failures of both tensile and stress-rupture specimens occurred in the base metal.

Saraç, İsmail ( Aksaray, Yazar ), Nano-technological developments, which have made significant progress in recent years, have significant impact on the science of adhesives. Therefore, in our study, the static and fatigue strengths of single-lap joints (SLJs) incorporating nanoparticles were compared to those without nanoparticles. Steel plates were used in the adhesive joints. The results revealed that average damage load increased significantly in nanoparticle-reinforced adhesive joints. The highest damage load was obtained with 4 wt% nano-Al2O3 in epoxy adhesive. As the average damage load increased, the locus of damage changed from interfacial to the mixture of interfacial and cohesive. Also, fatigue strengths of the joints increased when the adhesive joint had nano-Al2O3 and nano-SiO2, and decreased when the adhesive joint had nano-TiO2.

Coatings on the surface of nodular cast iron were prepared using a continuous wave semiconductor laser as a function of laser power. The cross-sections were etched by aqua regia to reveal the microstructure, and then the surfaces were examined by optical microscopy (OM) and scanning electron microscopy (SEM). The phase composition was analyzed by X-ray diffraction (XRD), and the hardness was measured using a Vickers hardness tester. The wear behaviors were examined using a microscopic wear test machine. The results revealed that the microstructure of the coatings was mainly composed of martensite and austenite. As the laser power increased, a wider columnar dendrite zone and an equiaxed dendrite zone can be observed, and the proportion of martensite decreased and retained austenite increased. The hardness first increased and then decreased with the increasing laser power. Solidification cracking was detected at higher laser power. All the worn surfaces at different laser powers exhibited typical adhesive wear, and the coatings with more martensite had better wear resistance.

This paper aims at understanding the microstructural evolution during the dissimilar brazing of γ-TiAl intermetallic to a Ni-based superalloy by using a novel high-entropy quinary amorphous TiZrNiCuCo filler alloy. Three distinct zones were characterized in the joint region: reaction layer adjacent to the γ-TiAl, diffusion zone in the IN718 side, and centerline solidified zone. Ti-Ni (Cu)-Al intermetallic compounds were formed in the reaction layer. αʹ (Cr, Fe) and γ (Fe, Ni) have precipitated in the γ-Ni matrix of the IN718 substrate discontinuously. The middle TiNi phase solidified isothermally during bonding. The maximum shear strength of 396 MPa achieved at 1020 °C for 40-min bonding, and the high temperature strength was 67% of the room temperature strength.