In the present research work, a highly wear resistant nanostructured WC-10Co-4Cr cladding has been deposited on AISI-304 stainless steel substrate by using TIG welding process. The WC-10Co-4Cr ...feedstock powder and claddings developed at different processing conditions were characterized by using FE-SEM, EDS, and XRD analysis. Microhardness and fracture toughness values of the deposited claddings have been evaluated by using Vickers hardness tester. Abrasive wear testing has been conducted by utilizing pin-on-disc tribometer against the SiC abrasive counter surface. TIG cladding process parameters were optimized by employing the central composite design based upon response surface methodology. The results revealed that the welding current has the maximum influence on the hardness and wear resistance of claddings followed by welding speed and standoff distance, whereas, argon gas flow rate has the minimum impact. The developed mathematical models for hardness and wear have been validated. The error between the experimental and predicted values lies within the acceptable range. Microstructural examination revealed that material removal has occured due to the pull-out of WC grains and eruption of soft CoCr matrix caused by the SiC abrasive particles during the sliding motion.
•A nano-structured WC-10Co-4Cr cladding deposited on steel specimen by using TIG welding.•RSM technique is used to optimize the hardness and abrasive wear of claddings.•Current and speed have maximum influence on the abrasive wear behaviour of claddings.
The present research investigates the effect of process parameters on the microstructure, micro segregation, and material properties of the Autogenous Double Pulse Tungsten Inert Gas Welding ...(ADP-TIG) of Inconel 625. The optimization of the process parameter was evaluated by Response surface Methodology (RSM) Box Behnken method. In this article, the effects of the weld-bead geometry, weld centre (WC), weld interface (WI), and heat affected zone (HAZ) were evaluated through macro morphology, microstructure, SEM/EDAX, XRD, and micro hardness. The outcomes indicate that by employing a combination of high and low frequency pulsing in ADP-TIG, it is possible to regulate not only the dimensions of the weld-bead and penetration depth but also the HAZ. The ADP-TIG process has a low heat input, resulting in finer grains in the microstructure, reduced secondary phases, and a narrower HAZ. SEM images of alloy 625 confirms the depiction of fine equiaxed dendrites. The ADP-TIG process reduces secondary phase formation due to a reduction in Mo and Nb alloying elements. EDAX results also show that the micro segregation in the weld centre (WC) and weld interface (WI) is very less in the dendritic core region because of the lower heat Input. The XRD result confirms the presence of NbzNi, Cr₂Nb, Ni8Nb, Fe2Mo3 and FeNi phases. The maximum microhardness values in WC and WI are 290 HV and 280 HV, respectively. The impacts of ADP-TIG welding technique specifications on factors such as weld bead geometry, WC, WI, and HAZ have been thoroughly examined across a range of process parameters. Further the process parameters of ADP-TIG were optimized using a desirability function to achieve defect-free welds, followed by experimental validation. The desirability function results were then compared with a machine learning (ML) approach. The investigation aimed to assess ML algorithms' predictive capability for weldment outcomes. From the ML modelling results, Support Vector Machine (SVM) using the Radial Basis Function (RBF) kernel was identified as the superior strategy for accurately predicting Heat input, Mo segregation, and Nb segregation. Additionally, Gaussian process regression (GPR) with an RBF kernel was recommended for predicting the Width to Depth Ratio.
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•This article examines the novel welding technique of ADP-TIG to join without filler wire using high temperature applications.•The Optimize the process parameters using both RSM and machine learning algorithms of (SVM, RBF, PUK GPR) approaches.•The DP-TIG technique reduces the heat input and segregation found in all 15 runs.•The DP-TIG weldments are test by macro, micro, SEM, XRD and Hardness for all 15 runs.•The desired function approach and the ML algorithm is frozen by the optimised parameter and output response.
The mechanical properties of AlLi alloy joints are closely related to the composition of the welding consumables. The present study aims to improve the mechanical properties of 2195 AlLi alloy joints ...by adjusting the filler wire composition. The 2195 AlLi alloy filler wire (same composition welding, SCW) and a self-designed filler wire (dissimilar composition welding, DCW) are used for the TIG welding of 2195 AlLi alloy sheets in this study. The results reveal that increasing Cu concentration in the filler wire leads to more eutectic formation in the DCW weld, and the possible solidification crack can be healed in time by the liquid metal in the final solidification stage; significant grain refining in the DCW weld is caused by adding Ti and Zr into the filler wire, the refined grains enable the joint to tolerate more plastic deformation and reduce the continuity of the eutectics along the grain boundaries. The positive effects of filler wire composition adjustment on the joint mechanical properties are verified by the mechanical tests. The plastic deformation is concentrated in the weld, and the weld elongation of the DCW joint is much higher than the SCW joint. In addition, the solidification crack can be observed in the SCW joint but not in the DCW joint. These findings can guide the design of subsequent filler wires matched to 2195 AlLi alloy.
•The microstructure evolution mechanism of the grain refinement and solidification crack controlling was revealed.•The influence of Cu concentration in the filler wire on the solidification crack formation in the weld was discussed.•The effect of adding Ti and Zr in the filler wire on the mechanical properties of the joint was discussed.
In the present day, the joining of dissimilar metals used in the same industry applications is of great interest. MIG and TIG welding processes are among the most common methods used to join ...dissimilar metals with high strength and reliability. Due to the different mechanical properties of dissimilar metals to be joined by these welding methods and welding parameters, they must be carefully selected. In this study, the effects of Total Accumulated Weld Volumes (TAWV) and different groove angles (45°, 60°, 75° and 90°) on the mechanical properties of AISI 1040 and AISI 8620 cylindrical steel joints were investigated experimentally. In addition, the fracture surfaces of the samples were examined by scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX). In the process with MIG and TIG welding, only current and voltage changes were made in order to measure the effects of parameters on the mechanical properties of the joints more clearly. As a result of the studies, the highest average Ultimate Tensile Strength (UTS) was 579.611 MPa and the lowest average UTS value was 424.611 MPa. Based on TAWVs, the highest average UTS value was obtained in TIG welded joints, and the lowest average UTS value was obtained in MIG welded joints. It was observed that the UTS values of the joints were positively affected by the increase in TAWV. The UTS value of the 90° groove angled joint was found to be 40.25% higher than the UTS value of the 45° groove angled joint.
•A SPH-model for TIG-welding, including welding speed, temperature dependent material properties and arc influences.•Surface movement due to pressure, shear, gravity, marangoni effect.•Small ...particles and large model to reach quasi-stationary state during the welding process.•Resulting welding penetration is compared to experiments with good agreement.•Weld pool flow, weld pool form and temperature distribution are discussed using the model.
A three-dimensional computational weld pool model for TIG welding is described. The model is based on the smoothed particle hydrodynamics method and takes various forces in the weld pool into account including shear stress and arc pressure, surface tension, marangoni effect, gravity and the welding speed. The numerical results are compared to cross sections from experiments for different welding currents and show a very good agreement. The model is then used to describe the weld pool dynamics and the formation process of the weld penetration as well as the temperature distribution in the weld pool.
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This study investigates dissimilar metal weldments between P91 steel and AISI 316 L austenitic stainless steel fabricated by activated TIG welding (A-TIG) with and without the use of ...interlayers of Incoloy 800 and Inconel 600. Through thickness penetration in 8 mm thick plates was achieved in a single pass A-TIG welding using a pre-coated mixture of metallic oxides. Hot cracking was eliminated in A-TIG weld joints in contrast to conventional TIG weld joints without flux. Fully martensitic structure was observed in the weld metal developed without the use of interlayer. Microstructural modifications were achieved with the use of interlayers. The weldment with Incoloy 800 interlayer exhibited martensitic-austenitic structure whereas fully austenitic structure was observed with Inconel 600 interlayer. Interlayers improved impact toughness and ductility of the weld joints without significant loss of tensile strength. The effect of interlayers on carbon migration after aging treatment (620 °C/500 h) was evaluated with the help of thermodynamic simulations and it was observed that the use of interlayers reduced the severity of carbon migration.
Ultrasonic assisted tungsten inert gas welding-brazing technology was developed to refine coarsening columnar α-Mg grains of Mg/Ti joints. In this study, ultrasonic vibration was introduced into ...molten pool of Mg/Ti joints with frequency of 20 kHz and maximum power of 1·6 kW. The results showed that, with ultrasonic power of 1·2 kW, the morphology of columnar α-Mg grains was refined to approximately equiaxed grains and the average grain size of columnar grains decreased from 200 to ∼50 μm. Moreover, the maximum joint strength of joints increased ∼18·1% to 228 N mm
−1
over the joints welded without ultrasonic vibration (193 N mm
−1
). Furthermore, the optimised Mg/Ti joint fractured at base metal zone rather than fusion zone upon tensile-shear loading, indicating that efficient grain refinement was attained. However, welding voids occurred with the ultrasonic power further increased to 1·6 kW, which resulted in the decrease in mechanical properties.
The aim of the work was to determine the structure and hardness of the parent material, the heat affected zone and the weld in butt joints of thin sheets with a thickness of 1.0 mm made of Inconel ...625 nickel superalloy welded by TIG (tungsten inert gas) method. Test joints were made with different linear welding energy in the range of 70 - 145 J/mm. The obtained welded joints were subjected to visual tested, macroscopic metallographic examinations, observations of the structure on a light microscope, observations of the structure in a scanning electron microscope and a hardness measurement. The geometrical parameters of the joints were also specified. Chemical composition of structural components of selected areas of the weld, heat affected zone and parent material was determined by surface and point X-ray microanalysis. The range of linear energy was determined in which joints of thin sheets made of the tested superalloys in laboratory conditions show the best quality.
The attractive mechanical properties of 7075 alloy, such as its high strength-to-weight ratio and fracture toughness, have received special attention in the automotive and aerospace industries. ...However, welding as a fabrication process has a detrimental effect on this alloy’s properties which affects its mechanical performance. In this work, to compensate for the loss in mechanical properties caused by welding, proper heat treatment operations are adopted. To this end, 1.5 mm AA7075 sheets were first preheated and butt welded using the gas tungsten arc welding process. The welded sample was solution heat treated, quenched, and then artificially aged. Microhardness tests showed an increase of hardness in all zones of the aged specimen compared to those of the original welded blank before heat treatment. A maximum microhardness value of 180 HV was recorded in the heat-affected zone of the aged specimen. In addition, elongation at break, and strength (yield, tensile, and fracture) of the original welded blank increased by about 50% after the artificial aging operation.
The work is focused on examining the influence of heat treatment modification during post-weld heat treatment on microstructure and mechanical properties of dissimilar welds of T91 and Super304H. ...Tungsten inert gas (TIG) welding was employed with ERNiCr-3 as filler to prepare the dissimilar metal welds. Following that, two post-weld heat treatments (PWHTs) were performed, viz. post-weld normalizing and tempering (PWNT) and post-weld direct tempering (PWDT). The latter was performed at 760 °C for 1 h, while the former was carried at 1050 °C for 30 min (normalizing) and then tempered at 760 °C for 1 h. The microstructural examination using scanning electron microscopy and electron-backscattered diffraction suggested a uniform microstructure after PWNT compared to PWDT. For instance, the grain size range in heat-affected zone for T91 side and Super304H side was 5–80 μm and 10–140 μm, respectively, after PWDT, while it was respectively reduced to 5–35 μm and 10–60 μm after PWNT. Further, the PWDT heat treatment resulted in coarse Cr-carbides at grain boundaries (~ 671 nm), indicating sensitization on the Super304H side, whereas the PWNT heat treatment ensured small Cr-carbides (~ 504 nm), indicating that the sensitization phenomenon was delayed. Further, on the T91 side, the vulnerability of fine-grained heat-affected zone for type IV cracking has been identified and eliminated through PWNT treatment. The improved microstructure of PWNT against PWDT heat treatment correlated well with the enhanced mechanical properties, where 0.2% proof stress, tensile strength, % elongation and toughness for PWDT were 324 MPa, 649 MPa, 20%, and 109 MJ/m3, respectively, while after PWNT, these were improved to 384 MPa, 691 MPa, 22%, and 132 MJ/m3, respectively. For both treatments, failure was observed in the weld metal region due to coarse Nb/Ti intermetallic carbides.
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•Post-weld normalizing and tempering (PWNT) established for dissimilar welds.•PWNT reduced the heterogeneity in microstructure and mechanical properties.•On the Super304H side, the sensitization tendency reduced after PWNT.•PWNT was effective in reducing the type IV cracking on the T91 side.
