Journal of Welding Science

316 steel is used in transportation, space, and chemical equipment. This steel is in demand in these industries due to its durability. It is used to increase the lifespan and renovate equipment. The research explores the impact of laser energy density on st6 cladding. It specifically focuses on the microstructure and geometric characteristics of the cladding. The cladding is applied on 316 steel. The experiment was designed with energy density changes from 40 to 116 J/mm and powder rate changes between 12 and 20 g/min. Optical and electron microscopic images were used to evaluate the samples. The results indicated that the dendritic arms grew larger with increased energy density. The dimensions increased from 1.5 to approximately 3. In other words, the speed of cooling is doubled. Increasing energy density from 40 to 75 J/mm reduced cobalt to chromium ratio from 2 to 0.7. It also decreased cobalt to iron ratio from 35 to 3. The changes emphasize how energy density affects microstructure and phase transformations.

In this study, the effects of friction stir welding (FSW) parameters on the properties of dissimilar joints formed between 5083 aluminum alloys and 316L austenitic stainless steel, with a thickness of 4 mm, are investigated. The tool speed is varied in the range of 16 to 25 mm/min, while the tool rotation speed is maintained at a constant value of 250 rpm. To examine the microstructure of different weld regions, both optical and scanning electron microscopes are employed. To assess the mechanical properties, hardness and tensile tests are conducted. The results shows the formation of a composite region characterized by steel reinforcement particles dispersed within an aluminum matrix. At the steel-aluminum interface, a single layer of discontinuous intermetallic composition with a thickness of approximately 2 micrometers is observed. Notably, when the rotation speed is set to 250 rpm and the tool speed is 16 mm/min, a tensile strength of 298 MPa and ductility of 26% (93% of the tensile strength and 50% of the ductility of the 5083 aluminum alloy) are achieved.

Society's great and growing demand for buildings and structures has created the need to apply new construction methods to shorten construction times, make buildings lighter, extend their useful life, and make them more earthquake-proof. In the long term, the new methods will lead to structural optimization, increased building performance, and the achievement of optimal operating conditions. New technologies are meeting society's increasing need for special structures more than ever. Additive manufacturing is based on gas metal arc welding as one of the fastest and most cost-effective manufacturing methods for primary metal structures. For this purpose, the three parameters voltage, wire feed speed, and welding speed were considered initial parameters affecting the width and height of the welding flux. To investigate the effects of the process,

16 experiments with input parameters were evaluated. The width and height of the sweat pollen were determined by experimental investigations. Subsequently, the resulting welding geometry is modeled using three numerical modeling methods, including intensive learning machines, relevence vector machine, and fuzzy logic. The comparison between the experimental data and the results of the three generated models shows that fuzzy logic comes closest to the experimental data of the welding geometry of the modeling methods. For example, the test data of the generative fuzzy model resulted in an average error for height and width of 0.667 and 0.5477, respectively, and a root mean square error for height and width of 0.0046 and 0.3, respectively, which expresses the generalization ability and reliability compared to other modeling methods in this process. Finally, a metal pattern of a special structure was produced based on arc and wire additive manufacturing based gas metal arc welding.

In this study, the microstructure and mechanical properties of dissimilar resistance spot welding of AISI 430 steel and S500 MC steel were investigated. To carry out this research, Taguchi's L9 array was used to determine the number of samples and determine the range of variables of each sample, and after welding the samples and performing the shear tensile test, the sample with the highest tensile shear strength (13740 N) and the highest amount of fracture energy (102160 Joules), was considered as the best example; Also, the variables of this sample, i.e., welding current of 12 kW, welding time of 12 cycles, and electrode force of 3 kN, had the highest signal-to-noise values, and these values were chosen among the best range of variables among the proposed variables. Then, a microhardness test was performed on the welded sample with the above variables, and microstructural studies were performed by optical microscope and scanning electron microscope. The hardness of the weld zone was observed to be about 400 Vickers, and the microstructure of the weld metal consisted of ferrite, martensite, and Widmannstatten ferrite.

This research studied the effect of two-stage over aging treatment on the pitting corrosion behavior and microstructure of the weld metals in the 17-4 precipitation hardening stainless steel. For this purpose, this steel was subjected to solution annealing heat treatment at 1035°C for one hour before welding. Then gas tungsten arc welding (GTAW) was performed using ER630 similar filler metal. Subsequently, a section of the weldment was subjected to two-stage over aging treatment. The microstructure and corrosion resistance of the weld zone after the two-stage over aging treatment were investigated and compared with the weld zone behavior in the as-weld condition. Microstructural studies showed that the two-stage over aging treatment of the weld zone led to the tempering of the martensitic, the formation of more reversed austenite, and the formation of α-ferrite. The volume fraction of austenite in the as-weld condition was approximately %7 and increased to about %30 after two-stage over aging treatment, a four-fold increase. The pitting potential (EPit) of weld metal was -18.15 mv in the as-weld condition and reached 122.54 mv after two-stage over aging treatment, which also signifies an improvement in pitting resistance. The two-stage over aging treatment also reduced the potential differences between the different parts of welding zones reducing the galvanic corrosion occurrence. The assessment of mechanical properties through impact test revealed that impact resistance after

This study aimed to investigate the effect of diffusion welding parameters on the microstructural characteristics and mechanical properties of the dissimilar joint between AISI 418 stainless steel and Inconel 738 superalloy using Ni interlayer with a thickness of 50 µm. The experiments were performed in a vacuum furnace at three temperatures of 1000, 1050 and 1150 °C for 45, 60, 75 and 90 min under the pressure of 5 MPa.The results show that voids and non-bonded areas are seen in the samples that were bonded at a lower temperature (1000 °C). By increasing the joining temperature from 1000 °C to 1050 °C, all micro discontinuities have disappeared, which shows that the microplastic deformation of roughness has improved. Then, by increasing the temperature to 1150 °C,non-bonded areas are observed in the joint due to the reduction of pressure on the contact surfaces. When pure nickel is used as an interlayer, intermetallic compounds of
γ' [Ni3(Al, Ti)] are formed in the γ matrix phase on the side of Inconel 738 superalloy while compounds of FeNi3 and γ (γFe, Ni) are formed on the side of AISI 418 stainless steel. According to the results of line scan analysis, the slope and penetration of elements in Inconel 738 superalloy is lower than AISI 418 stainless steel , which indicates less penetration in Inconel 738 superalloy. In the sample welded at the temperature of 1050 °C and the time of  90 Min, the penetration value of the nickel interlayer in AISI 418 stainless steel  and Inconel 738 superalloy was 40 µm and 35 µm, respectively. By comparing the maximum hardness, it can be concluded that the joint at the temperature of 1050 °C and the time of 90 Min has a lower maximum hardness than other samples. Therefore, it has better joint characteristics than other samples in terms of intermetallic compounds. The highest value of shear strength was obtained at the temperature of 1050 °C and the time of 90 Min, which is equal to 270 MPa.

The present study focuses on optimizing the mechanical properties and microstructure of laser welding in Haynes 25 (L-605) cobalt-based superalloy. Initially, the influence of laser welding variables such as laser power, pulse frequency, welding speed, and pulse width on the mechanical and metallurgical properties of the weld joints is investigated. By examining the welding variables, the values of G (thermal gradient) and R (cooling rate) are calculated, and their ratio (G/R) and cooling rate (G×R), which predominantly affect the solidification microstructure, are determined. The structural correlation with the mechanical properties resulting from welding is examined.  In this research, it is considered to obtain the welding variables to create a high percentage of the structure in the form of equiaxed dendrite. Microstructural analysis reveals the growth of equiaxed grains and dendritic structures in the weld zone. The high cooling rate in the weld pool leads to dendritic solidification starting from columnar dendrites at the weld walls and ending in equiaxed dendrites at the center of the weld. The microhardness value in the weld zone is HV 328, which is very close to the microhardness of the base material. The tensile strength of the weld samples reaches about 93% to 94% of the base metal tensile strength. Tensile testing of the weld samples indicates a ductile-brittle fracture. Examination of the scanning electron microscope confirms the presence of dimples, intergranular cracks, and microvoids in the fracture zone.

In today's technological landscape, the push for miniaturization in electronic devices is greater than ever, driven by technological advancements.The challenges of electromigration and thermomigration
have arisen due to the need to establish new electronic connections under conditions characterized by creeping temperatures, originating from the low melting point of solders and high current density.  Therefore, recently, alloying and composite materials have been employed to enhance the resistance of electronic connections to electromigration. In this study, efforts to enhance the resistance to electromigration using a composite SAC0307 lead-free solder alloy incorporating cobalt microparticles. The presence of cobalt in the intermetallic composition of the interface causes more stability of the intermetallic composition of the interface and prevents the reduction of the thickness of the intermetallic composition of the interface during the time of the electromigration test; As a result, the stability and electronic connection of the sample soldered with composite solder alloy is more than that of non-composite solder alloy. On the other hand, due to the fine grain structure and the increase in grain boundary density in the composite solder alloy, the lattice diffusion mechanism in the non-composite solder alloy has been changed to the grain boundary diffusion mechanism; As a result, due to the consumption of copper atoms flowed from the cathode side to the anode by the intermetallic compounds present in the grain boundaries, non-uniform microstructural was observed in the composite solder alloy during the time of electromigration test.

In this research, the transient liquid phase bonding of St52 carbon steel to WC-Co cermet using a copper interlayer with 50 μm thickness was done. For this purpose, samples were jointed to each other at a constant temperature of 1100 ºC and bonding times of 1, 15, 30, and 45 min. The microstructure of the joints was examined using an optical microscope and scanning electron microscope equipped with energy-dispersive X-ray spectroscopy. XRD analysis was also used to investigate the effect of bonding on the phase changes of the bonding area. Microhardness and tensile shear tests were also conducted to study the mechanical properties of the samples. Microstructural investigations showed the formation of three different zones including isothermal and athermal solidification zones and DAZ in the WC-Co base material side, which determine the characteristics of the samples. The isothermal solidification zone contained a Fe-rich solid solution and the athermal solidification zone contained a Cu-rich solid solution. η phase was not formed in the DAZ of WC-Co cermet at bonding times of 1 and 15 min. This phase was formed in the DAZ of WC-Co cermet by increasing the bonding time to 30 and 45 min. The microhardness studies showed that all samples had the same trend. Maximum microhardness was 1100 HV which was related to WC-Co base cermet and the lowest microhardness was about 220 HV which was related to steel base metal. Also, the maximum tensile-shear strength of the bonded samples was about 180 MPa for a bonded sample at a bonding time of 15 min, which was due to the increase in the volume fraction of iron-rich solid solution, as well as proper microstructural continuity and the presence of an optimal amount of copper-rich phase in the microstructure.