Experimental investigation of the impact of GMAW welding parameters on the mechanical properties of AISI 316L/ER 316L using quaternary shielding gas

In this study, the parameters of Metal Inert Gas (MIG) and Metal Active Gas (MAG) were investigated of AISI 316L/ER 316L. A quaternary shielding gas mixture consisting of Argon (Ar), Helium (He), Carbon Dioxide (CO2), and Nitrogen (N2) was chosen. The Taguchi orthogonal array (OA-L9) methodology was employed to explore optimal welding settings, including arc current (120A, 160A, 200A), wire feed rate (3, 3.5, 4 m min−1), and shielding gas combination (G1, G2, G3). The findings highlighted the importance of shielding gas in influencing the ultimate tensile strength (UTS), elongation percentage (EL%), and material toughness of welding joints. Notably, the highest UTS (515.77 MPa), EL% (20.85%), and material toughness (133J) were achieved by the specific group gas combination shown as G1. It is recommended to configure welding parameters to an arc current of 160A, a wire feed rate of 4 m min−1, and the G1 gas combination. Welded specimens using a G1 gas mixture showcased the best UTS and EL%. Additionally, it was found that the fusion zone (FZ) and heat-affected zone (HAZ) hardness are most profoundly influenced by the choice of gas combination (G2), resulting in the best hardness values of 253.79 HV and 239.68 HV, respectively. The optimal parameters for achieving the desired material hardness were precisely identified as (120A, 3 m min−1, G2). These insights offer a pathway to enhance welding performance and, in turn, elevate the quality and efficiency of industrial applications.


Introduction
MIG/MAG welding processes, commonly known as Gas Metal Arc Welding (GMAW), is a common welding process in various industries.The welding process requires the use of a consumable electrode wire.The wire is fed continuously through a welding gun at a controllable rate meter per minute (m/min), this leads to a welding process that is characterized by its smoothness and efficiency.An electric arc created between the wire and the metal being welded melts the wire electrode.The MIG and MAG welding processes have become widely used in a variety of industrial applications [1].This process has gained popularity due to its versatility and effectiveness in joining metals.It is used in automotive, pipe welding, construction, etc because of its ability to weld various materials.Including stainless steel, aluminum, mild steel, etc This process provides high-quality welds with minimum post-processes [2].This makes them ideal for high-volume manufacture.Also, using shielding gas has the purpose of protecting the welding pool against contamination from atmospheric aspects, which may manifest as flaws [3].
Shielding gas protects the welding area from pollutants including dust, dirt, moisture, or gases from the surrounding environment.These pollutants have the potential to interfere with the quality of the weld or compromise the integrity of the materials being joined.The shielding gas can be used as an inert or active gas, depending on the base material, welding procedure employed, and application.High-quality welds require the use of an appropriate gas for each application.The shielding gases used are Ar, He, N 2 , CO 2, and Oxygen (O 2 ).such as in marine environments, chemical applications, and medical devices, due to its excellent corrosion resistance properties [22].The mechanical properties of AISI 316L can be influenced by various welding parameters.Arc welding current, voltage, speed, shielding gas combinations, and electrode feed rate.These parameters greatly affect welding strength and geometry.These parameters will influence elements such as heat input (current, voltage) and cooling rate distribution (shielding gas).Therefore, it greatly impacts mechanical properties, such as UTS, EL% toughness, and corrosion resistance.It is crucial to optimize welding parameters to achieve the desired mechanical properties [23].
Taguchi analysis is a statistical method for optimizing parameters that can affect any process.The application of several experiments and unrelated to each other.Then study the parameters that affect the process used and measure performance.It is necessary to optimize welding settings to achieve mechanical properties.Taguchi analysis improves MIG/MAG welding properties and efficiency by optimizing parameters as reported by Khrais et al [23].Also, they used the Taguchi approach to determine and optimize welding parameters.It is found that the shielding gas has the greatest influence on angular distortion and arc current on bead geometry.This research demonstrates the importance of controlling welding parameters.Furthermore, Ogbonna et al [24] optimized the Gas GMAW process for a butt joint between AISI 1008 mild steel and AISI 316 austenitic stainless steel using a hybrid Grey-based Taguchi method.The welding parameters considered were arc voltage, arc current, and gas flow rate.They found that Voltage was identified as the most significant process factor, contributing 63.76% to the overall performance of the weldments.So, the optimal welding parameters were the arc current of 180 A, the arc voltage of 14V, and a gas flow rate of 19 (L/Min).At these settings, the weld joint exhibited improved performance characteristics, including a tensile strength of 559.25 MPa, yield strength of 382.22 MPa, a percentage elongation of 33.34%, and a hardness of 250.63 HV.In addition, Ghosh et al [25] optimized MIG welding parameters of AISI 316L austenitic stainless steel.The study's parameters include gas flow, nozzle distance, and arc current.The best MIG settings were 100A arc current, 20 l/Min gas flow, and 15 mm nozzle distance, according to the researchers.
Many factors influence MAG/MIG welding and are essential in determining the quality and integrity of the weld.The arc current has a significant impact on the size, formation, and mechanical characteristics of the grain.Using a high arc current could lead to the formation of larger grains, thereby reducing the toughness and ductility of the material.On the other hand, using a low arc current may promote the formation of smaller grains, leading to an improvement in toughness and ductility [26].The wire feed rate has the most strongly major effect on the geometry of the bead, the depth of penetration, and the size of the grains.Furthermore, it is worth noting that higher wire feed rates lead to increased depth of penetration but also result in larger grain size, while lower wire feed rates may lead to decrease depth of penetration and a smaller grain size [27,28].The mechanical properties of the weld can be affected by the choice of shielding gas combination and flow rate since they serve to protect the weld from contamination in the surrounding environment.Increasing the flow rate of the shielding gas can enhance the welding performance and prevent failures [12,29].Taguchi methodology is employed to optimize welding parameters and establish guidelines for improving mechanical properties through the utilization of quaternary shielding gas.This approach significantly enhances understanding of welding processes, material quality, and operational efficiency in industrial settings.The careful selection of appropriate parameter values ensures that welds are free of imperfections and have the desired mechanical properties.
This research aims to investigate the MIG/MAG welding parameters, namely arc current (amperes), wire feed rate (meters per minute), and different types of quaternary shielding gases (G1, G2, G3) impact the welding properties of AISI 316L.The investigation of welding properties involved the application of the Tensile strength test, Charpy impact test (CIT), and Vickers hardness tests (HV).Additionally, a comprehensive analysis of the microstructure will be conducted through the utilization of Energy-dispersive x-ray spectroscopy (EDS) and Scanning Electron Microscopy (SEM).Moreover, this research presents an innovative methodology in the application of quaternary shield gas.This study enhances our understanding of the individual utilization of each gas ratio.The responsibility for regulating these gases is entrusted to professionals.

Experiment setup
A compact 410 machine was utilized in this investigation.It is designed for high-quality stainless steel, alloy steel, and aluminum welding.There is a high operating role of 400 amps, as well as a high degree of amp-rate control and wire feed rate control.It also has great safety characteristics in industrial applications.

Material
The sheet has a thickness of 5 mm, it has been cut into 100×100 mm 2 .The edges have been cut at an angle to produce a weld groove gap, which is the space or separation between the root surfaces of the V-groove in the weld zone.a single 45-degree and the total V-groove (90-degree) in the weld zone, as shown in figure 1.The depth of the bevel is 3 mm, the root is 2 mm, and the root opening distance is 1 mm.The UTS of AISI 316L stainless steel is around 560 MPa, with Vickers hardness (HV) values is 152 HV.The impact toughness value, measured by Charpy impact testing, is reported as 103 joules.Table 1 shows the chemical composition of the AISI 316L sheet.

Filler material
ER 316L wire is made per ISO 14343-A and AWS A5.9/A5.9Mstandards and has a diameter of 1 mm.It also has mechanical properties such as tensile strength, yield strength, and EL% (550MPa, 350MPa, 35%).The ER 316L features may be employed in welding at a variety of positions (horizontal, flat, vertical, overhead).The chemical composition of ER 316L is shown in table 2.

Shielding gas composition
The G1, G2, and G3 are gas combination groups with a specific ratio of Ar, He, N 2 , and CO 2 .The gas flow rate of the quaternary gas combination is 18 l M −1 in −1 and is controlled at each cylinder port.There are four types of gas cylinders as shown in figure 2. The mixing and regulation of the shielding gas occurs within the confines of the gas cylinder or supply source, where the pressurized gas is securely stored.To attain this, a regulator (valve) and a flowmeter are harnessed to reduce the gas pressure to an appropriate degree and control the flow rate, quantified either in liters per minute (L/M) or cubic feet per hour (CF/H).Then, the shielding gas is channeled through a conduit, such as a hose or tubing, leading it to the welding torch or gun.In proximity to the tip of the torch or gun, a gas nozzle or diffuser disperses the gas through minute apertures, ultimately forming a safeguarding ambiance protecting the welding arc and the molten weld pool.The precise composition of the shielding gas is meticulously customized to harmonize with the specific welding application and the materials in use.Prudent mastery of both gas flow rate and composition becomes an indispensable factor in achieving the sought-after weld quality and overall performance.To preserve the gas mixture's precision to two decimal points, it is crucial to employ the regulator valve to maintain a constant gas pressure and flow while welding.The recommended operating ranges for this purpose are between 0.021 to 0.05 MPa and 14 to 18 l min −1 , respectively [23].

Taguchi design experiment
Table 3 presents the experiment setup of the welding parameters and gas combinations used in nine samples of AISI 316L.The welding parameters include the arc current and wire feed rate, while the gas mixture includes four components: Ar, He, CO 2 , and N 2 , and three different gas combinations (G1, G2, G3) were utilized.Sample No. 1, 6, and 8 were welded using Gas 1, while Sample No. 2 and 9 were welded using Gas 2, and Sample No. 3, 5, and 7 were welded using Gas 3. The percentages of each gas mixture were different for each sample.Fixed MIG/ MAG parameters were employed, including an arc voltage of 380 Volts, a gas flow rate of 18 l min −1 , and a Filler diameter of 1 mm.The noise factor in MIG or MAG welding is essentially the influence of various parameters on the quality and stability of the welding process.The primary parameters that affect the noise level (variability) in MIG/MAG welding include arc current, which influences heat input and weld penetration and can lead to inconsistencies in the weld bead; wire feed rate, which determines the amount of filler material added to the weld pool, affecting deposition rate and bead shape; and the shielding gas combination, crucial for protecting molten metal from contamination, with specific gas combinations and flow rates affecting arc stability and weld quality [30][31][32].

Experimental procedures
In the process of the experiment, an expert welding specialist manually welded nine different specimens together.The welding process for each AISI 316L sample was conducted following the Taguchi approach.The welding process was controlled and optimized based on Taguchi's experimental design and analysis methods, utilizing a Taguchi table to guide the process.Following the welding process, the samples were allowed to cool for an extended period, as shown in figures 3(a) and (b).After that, a computer-controlled milling machine was utilized to cut the nine samples at a slow cutting speed while simultaneously maintaining a high cooling rate [33] Finally, a representative sample was taken from each experimental test.

Characterization measurements
The present investigation was conducted within the controlled environment of the laboratories at the Jordan University of Science and Technology.A Universal Testing Machine pulls a flat specimen precisely during the Tensile Strength Test.The specimen's behavior is carefully measured.These ASTM E8-cut samples are 5 mm thick (Standard).Figure 5 displays the specimens before the test.CIT demonstrates materials' durability and toughness.Researchers assess energy absorbed by pendulum-striking a notched sample.Impact energy, ductile-to-brittle transition temperature, fracture surface analysis, and statistical analysis are revealed by the tests.It's like seeing the material's microstructure and unique features under extreme impact loads.Remember the outstanding HV Test.This well-known approach examines material hardness.Measuring the size of the indentation formed by pressing a pyramidal diamond into the material's surface with a specified weight and duration.HV number, depending on the applied load on the indentation surface area.

SEM and EDS
The utilization of SEM and EDS techniques is prevalent in the analysis of the microstructural properties and elemental components of welding joints.Collectively, these findings offer valuable perspectives on the characteristics and attributes of the joint, including the identification of flaws, the distribution of elements, and the development of intermetallic compounds.Furthermore, the provided information can be utilized to enhance the efficiency of the welding process and guarantee the quality and dependability of the final product.

Results and discussions
This study statically evaluates AISI316L/ER316L mechanical properties using the L9 Taguchi approach.Investigating the UTS, EL%, toughness, hardness, SEM, and EDS.The results of the mechanical properties are presented in table 4. The L9 Taguchi design may also quickly display several parameters and their interactions.By using this approach, it was able to systematically vary the experimental conditions and obtain reliable results.

UTS and EL% of AISI 316L/ER316L
UTS refers to the maximum stress that a material can endure before fracture when subjected to tensile loading.Moreover, the elongation at break (EL%) serves as an indicator of a material's ductility, representing its capacity to undergo deformation without fracturing.UTS and EL% are crucial properties used in engineering design to determine a material's strength, durability, and ability to weld joints of AISI 316L/ ER 316L to withstand deformation.
Figure 6(a) displays the difference in UTS values of the specimens made of AISI 316L/ER 316L, ranging from 405.92 MPa to 515.77 MPa.Hence, increasing the wire feed rate generally led to an increase in UTS values, up to a certain point, as seen in Samples No. 1, 2, 6, and 9.This is due to a greater deposition rate resulting in a more uniform and stronger welding.Similarly, an increase in arc current also led to a slight increase in UTS values, as   [34], as well as Kumaran and Raj [35].So, it's important to choose appropriate settings for optimal results.As shown in figures 6(a) and (b), the highest UTS and EL% values were observed in Sample No. 6, reaching 515.77MPa and 20.85%, respectively, when the MIG/MAG parameters of arc current, wire feed rate, and gas combination were set to 160A, 4 m min −1 , and G1.In contrast, Sample No. 2 had the lowest UTS value of 405.92 MPa when the MIG/MAG parameters were 120A, 3.5 m min −1 , and G2.For El%, Sample No. 7 had the lowest value at 14.22% when using the MIG parameters of 200A, 3.5 m min −1 , and G3.Moreover, different gas combinations impact the UTS of the welded specimens.The specimens welded using the G1 gas combination exhibited relatively higher UTS values compared to those welded using the G2 and G3 gas combinations.Ghumman et al [36] reported the UTS of AISI 316L typically within the range of 218.55 to 426.80 MPa.Additionally, the maximum EL% was 57.6%.This study found the highest UTS achieved with gas combination (G1) was 515.77MPa.Therefore, there was a significant increase in UTS compared to the welded material, from 421.80 to 515.77 MPa.The EL% decreased from 57% to 20.85%.
Samples No. 6 and 8, demonstrated that different combinations of arc current and wire feed rate can result in close values of UTS and EL%.Sample No. 6 used an arc current of 160A and a wire feed rate of 4 m min −1 , while Sample No. 8 used an arc current of 200A and wire feed rates of 3.5.These combinations of parameters resulted in a balanced heat input that allowed for good fusion and penetration without causing excessive softening or deformation of the material.The shielding gas group utilized also had an impact on the UTS results.For example, the Samples 6 and 8 using gas combination G1, as noted by Ghumman et al [36].Furthermore, an increase in the N 2 (6 vol%) content and moderate content of CO 2 (10 vol%) resulted in higher UTS and EL.% in the weld metals.The observed enhancement in the UTS can be ascribed to the elongated dendrites and enhanced inter-dendrite spacing (the branching, tree-like structures that form during solidification) that occurred during the solidification process.These parameters resulted in the formation of uniform delta ferrite and a refined grain dendritic structure within the welding zone (a phase in steel).The preservation of dendritic changes within the microstructural framework is a crucial part of improving the UTS.The results presented in this study align with previous investigations conducted by Costanza et al [37].which demonstrated that the gas mixture used in the welding process can successfully control the ratio of delta ferrite within the austenite matrix.
Industrial applications, especially in aviation, need a strong material to sustain wings, structures, support elements, and landing equipment, efficiency and safety depend on this [38].Also, bridges, towering constructions, and towers need joining materials with high tensile strength.Submarines and maritime constructions need materials that withstand waves and water pressure [39].Military vehicle's structure, armor, and ballistic protection have high UTS and EL% characteristics.Reinforcing heavy equipment and cranes using high UTS and EL% materials prevent expensive failures.High-EL% protects films, foils, plastics, and textiles during transportation and handling in the packaging and textile sectors.High-EL% materials in car body panels increase crashworthiness and energy absorption.Sample No. 6, which fulfills the specified requirements, exhibits the greatest UTS and has the highest EL% value.

Charpy impact test (CIT-toughness) of AISI 316/ ER316L
Welding joint toughness can be evaluated by performing a CIT.This test involves striking a specimen with a pendulum and measuring the amount of energy absorbed by the specimen as it fractures.Figure 7 shows the samples after performing the test.
Figure 8 shows that toughness values for the nine Samples range from 96 to 133.The different welding parameters can result in varying toughness values for the AISI 316L/ER 316L welding joint.Among the samples tested, Sample No. 6 had the highest toughness value of 133J, which was achieved using MIG/MAG parameters of 160A arc current, 4 m/min wire feed rate, and the G1 gas combination.In contrast, Sample No. 2 had the lowest toughness value of 96 J, which was produced using MIG/MAG parameters of 120A arc current, 3.5 m/ min wire feed rate, and G2 gas combination.Samples No. 1, 2, and 3 were tested using different wire feed rates (3-4 m min -1 ) and gas combinations (G1-G3), but they maintained the same arc current of 120A.It is worth noting that the shielding gas used in Samples No. 6, 8, and 9 (G1 and G2) created a more favorable environment for the desired AISI 316L/ER 316L toughness.The CIT values reported by Sriba et al [40] for AISI 316L were typically around 56 Joules.This study found the highest material toughness achieved was 133J with the gas combination (G1), indicating an improvement in toughness compared to the typical values for the base material.
Increasing the arc current in welding results in a higher heat input, which can lead to a larger FZ and deeper penetration.However, excessive arc current (200A) can lead to overheating issues.It may cause problems like the formation of brittle phases in the weld metal, which can compromise the structural integrity of the weld joint.These brittle phases can make the weld susceptible to cracking or other forms of failure, reducing the overall quality of the weld, specifically the material toughness.Conversely, a low arc current (120A) can result in poor fusion and reduced penetration, leading to lower strength and toughness.The limited heat generated at lower currents fails to fully melt the base materials, resulting in incomplete bonding and weak joints.This insufficient fusion and shallow penetration compromise the strength and toughness of the weld, diminishing its ability to withstand stress or load.Adjusting welding parameters, particularly arc current, is critical to ensure adequate heat for proper fusion and penetration, thereby preserving the desired mechanical properties in the welded materials.
On the other hand, an increase in wire feed rate typically leads to a higher deposition rate but also results in a coarser microstructure and lower toughness of the weld.Khrais et al [23] reported that decreasing the wire feed rate can result in a more refined microstructure which is reflected in the material toughness.Moreover, welding metal microstructure is also affected by shielding gas mixture composition.Due to their greater thermal conductivity and ionization potential than Ar and He.The N 2 and CO 2 have distinct impacts on material toughness in welding.N 2 tends to refine grain size, often boosting toughness, but excessive levels can lead to brittleness.On the other hand, CO 2 accelerates cooling rates, potentially strengthening the material but also risking increased brittleness.It's crucial to balance these effects: weighing N 2 's refining advantages against potential brittleness and CO 2 's strength benefits against the risk of brittleness.Optimizing their concentrations in welding is vital to maintaining the desired equilibrium between strength and toughness in welded materials.These gases serve as cooling agents during welding, hastening heat transfer and cooling to create finer, more consistent microstructures in the welded material.As reported by Kah and Martikainen [7], and Barbosa et al [41].
As a result, the G1 and G2 shielding gas groups produce finer and more homogenous microstructures in the AISI 316L/ ER 316L welding joint, which can increase material toughness.Because G1 and G2 gases have better thermal conductivity than other shielding gases.As a result of the increased ionization potential of G1 and G2, energy density and welding cooling are increased.Furthermore, higher wire feed rates improve welding speed and decrease HAZ, which enhances the toughness of an AISI 316/AISI 316L, but at high feed rate rates (more than 4 m/min), major spatter occurs, decreasing the joint's toughness.On the other hand, employing a high arc current may cause a bigger HAZ size, which reduces the toughness of AISI 316L/ER 316L, while using a low arc current can cause limited fusion and poor weld quality.Therefore, it is important to optimize these parameters to achieve the desired AISI 316L/ER 316L welding joint properties.
Construction requires tough material joints to protect buildings and infrastructure from dynamic loads and impacts [42].Armor and ballistic protection protect military and law enforcement personnel.Tough welding joint materials improve crashworthiness and survival in automobile, railway, and aerospace applications.Sportsmen use helmets and body gear.Durable materials endure oil and gas pressure [43].Strong maritime and offshore constructions can resist waves and smash [44].Medical and surgical tools must withstand constant usage and mechanical stress.Sample No. 6 has the highest AISI 316L/ER 316L material toughness and meets the requirements.

Vickers hardness (VH) of AISI 316/ ER316L
Figure 9 presents the average microhardness values in MIG/MAG welding that applied the load 10 Kg and Vicker hardness scale.All welding parameters have a notable impact on the welded material hardness.So, increasing the wire feed rate from 3 m/min to 4 m/min typically leads to a slight decrease in hardness, with some exceptions.The relationship of welding parameters is observed in the behavior between the gas combination (G1, G2, G3) and the feed rate (3-4 m min −1 ) of AISI316L/ER 316L.As a result, Sample No. 4 had the highest hardness value (253.79HV) in the FZ area.The welding parameters of the arc current (160A), wire feed rate of (3 m min −1 ), and shielding gas combination (G2) were employed.The weld's hardness was greatest at substantially reduced wire feed rates (3m/min), suggesting that decreasing the wire feed rates could enhance hardness in the FZ.Samples No. 6 and No. 8 had the lowest hardness values.Sample No. 6's welding parameters were 160A, wire feed rate (4 m min −1 ), and shielding gas combination (G1).Sample No. 8 also used a shielding gas combination (G1), the arc current of (200A), and the wire feed rate of (3.5m/min).The hardness values observed within the HAZ area display a variation ranging from (224.59 HV to 239.68 HV).Sample No. 4 has the highest recorded hardness value during relay to an arc current (160A), gas combination (G2), and a wire feed rate (3m/min).While, the lowest HAZ hardness Sample, No. 6, was welded using the gas combination (G1), arc current (160A), and wire feed (4 m min −1 ).Hence, the gas mixture and wire feed rate are only two of the interrelated parameters that influence HAZ hardness values.The AISI 316L hardness of FZ and HAZ values reported by Sriba et al [40] around 195.5 HV 178.7 HV.This study provided, the FZ and HAZ hardness values reached 253.79 HV and 239.68 HV, respectively, with the gas combination (G2).These values represent significant increases in hardness compared to the base material.
Both N 2 and CO 2 play roles in altering hardness during welding: N 2 can refine grain size and create solid solutions, potentially boosting hardness through finer grain structures.However, excessive N 2 levels can induce embrittlement, adversely impacting hardness.On the other hand, CO 2 , when integrated into shielding gas mixtures, accelerates cooling rates, leading to finer microstructures that often enhance hardness.Yet, elevated CO 2 levels might introduce brittleness, compromising both the hardness and toughness of the weld.As reported by Kah and Martikainen [7], and Barbosa et al [41].The variation in hardness is related to the amount of deltaferrite phase that is present in the weld metal, whereas the delta-ferrite was not detected in the HAZ and base metal.However, it was observed that the center zone of the weld exhibited varying hardness values when different MIG/MAG parameters were utilized during production.This phenomenon may be attributed to the role of the shielding gas that dissolves in the weld, ultimately increasing the amount of delta ferrite phase present within the austenite matrix of the weld metal.As supported by several studies including those conducted by Chuaiphan and Srijaroenpramong [30], Costanza et al [37] Kumar and Shahi [45], and Chandra et al [46].Achieving the right balance in their concentrations within the shielding gas mixture is critical to optimize hardness without sacrificing other mechanical properties in the welded material.
Joints welded with high hardness play a significant role in improving wear resistance.Their improved wear resistance and strength are particularly advantageous in applications involving wear, scratch, and impact [47].These joints hold the utmost importance in demanding industries such as construction, aerospace, and military tools.Furthermore, the high-hardness welding joints such as AISI 316L/ER 316L materials provide excellent corrosion resistance.Given their exceptional longevity, these joints are indispensable components in numerous applications.Samples No. 2 and 4 exhibit the highest level of material hardness, specifically in terms of AISI 316L/ER 316L welding joints.Furthermore, these samples successfully fulfill the specified requirements.
Hence, the observed percentage improvements in the study compared to typical values reported in the literature are notable.The UTS showed an increase of approximately 20.89%, while the EL% decreased by 62%.The improvement of material toughness exhibited approximately 137.5%.Moreover, the hardness both of FZ and HAZ increased approximately 29.83% and 34.09%, respectively.

SEM, EDS, and microstructure of AISI 316L/ ER316L
The microstructure of welded 316L stainless steel was analyzed in this study, with a focus on the impact of different shielding gas mixtures, arc current, and wire feed.Table 5 presents the findings of the EDS analysis.The study results indicated that the choice of shielding gas has a significant effect on the composition and microstructure of the welded metal.A shielding gas composition consisting of He, N 2 , Ar, and CO 2 resulted in a more austenitic microstructure with improved mechanical properties Sathiya et al [48].
The growth of grains in a smooth shape was observed when the wire feed rate was increased to 3 to 4 m min −1 , while a constant arc current of 160A was maintained.This effect was observed across different groups of shielding gas combinations (G2, G3, G1) and is shown in figure 10(a), figures 10(b), and (c).An increased amount of metal being deposited resulted from the increment in wire feed rate, leading to a larger welding pool and higher heat input.As a result, greater mixing and diffusion between the melted metal of the weld zone and the base metal were allowed, resulting in a more homogenous microstructure throughout the welded joint, as shown in Sample No. 4.
The HAZ was found to be very narrow, which is attributed to the higher heat input rate and faster cooling rate during the welding process as shown in Samples 4 and 6.It appears that the shielding gas composition G2, wire feed rate of 3 m min −1 , and current of 160 A had a negative impact on the FZ and HAZ, as shown in Sample No.5.The welding process with a rapid cooling rate prevented the formation of large grains in the HAZ and resulted in a more refined microstructure.
The differences found in the sizes of the HAZ in Samples No. 4, 5, and 6, as shown in figure 11(a), figures 11(b), and (c), can be attributed to differences in the wire feed rate.Sample 4, which had a wire feed rate of 3 m/min, showed a HAZ with a determined size ranging from 13.51 to 17.67 μm.In contrast, Sample 5 demonstrated the largest HAZ sizes, measuring between 33.39 to 39.09 μm, when a wire feed rate of 3.5 m min -1 was utilized.In the present analysis, it was observed that Sample No. 6 exhibited the smallest HAZ size, ranging from 2.924 to 7.047 μm, along with the highest wire feed rate of 4 m min -1 .
The wire feed rate at 4 m/min resulted in an increased formation of ferrite.The improvement of the ferrite grain structure was observed in figure 11(c).The formation of ferrite may be influenced by the cooling rate and chemical composition of the combination of welding shielding gas and filler material [49].The G2 welding process increased both FZ and HAZ porosity and contaminants, with measurements ranging from 13.51 to 17.67 μm.The presence of gas in the weld, known as porosity, is associated with the G2 composition.Nevertheless, the utilization of G1 composition in welding resulted in the production of better welds and a HAZ.The HAZ demonstrated a size range of 2.924-7.047μm.The HAZ is restricted to a restricted geographical area, thereby limiting the potential risks associated with changes in material quality.
As demonstrated, how HAZ size variation might alter specimen mechanical properties.Sample No. 5 may be weaker than Samples 4 and 6 due to its larger HAZ size.Larger ferrite grains may weaken welded solidarity.Sample No. 6's smaller ferrite particles may increase strength and toughness.Fine-grained structures improve mechanical characteristics.The welding process's base metal and filler material's chemical composition may affect ferrite formation and the weld's mechanical properties.As Bansod et al [16] observed this.
To optimize welded joint characteristics, welding conditions must affect HAZ and ferrite formation.Cracks and cavities in the welded region may grow with HAZ size.This may lower UTS and EL.%.Ferrite production, which is governed by wire feed rate and electrode wire diameter, may also impact its mechanical properties.Aguilar et al [50] and Kumar and Shahi [51] demonstrated that getting the required mechanical properties in a welded joint requires careful assessment of many aspects and modification of welding parameters.As shown in figure 12(a), the structure of the welded region reveals the presence of primary austenite (γ) grains, which exhibit a lighter appearance when observed under a microscope.These austenite grains are surrounded by a consistent matrix of grey ferrite (δ) grains.Upon examining the microstructures, it was observed that both the base metal and the FZ contain equiaxial grains of austenite and annealed twins, along with columnar dendrites of ferrite and austenite.Annealed twins occur when the crystal lattice of a material is duplicated through the process of annealing.
The microstructure of the FZ in this research is influenced by the composition of the filler metal, which in this case is AISI 316L.The microstructure of the welded stainless steel reveals an austenitic matrix accompanied by either dendritic or skeletal ferrite.This particular microstructure is commonly observed when welding is conducted at moderate cooling rates, which aligns with the conclusions drawn by Sathiya and Abdul Jaleel [31].
Figure 12(b) displays the solid particles known as precipitates that form at austenite grain boundaries during the welding process.High temperatures, rapid cooling, contaminants, and incorrect welding settings may all lead to their production.Applied suitable welding parameters setup can successfully reduce the precipitate formation.Thus, precipitates at grain boundaries may cause stress concentration and weaken the welded joint, increasing its failure probability.The material properties are influenced by the volume of precipitates, on which larger volumes result in decreased ductility, toughness, and corrosion resistance.Nevertheless, depending on their kind and the material being welded, small amounts of precipitates might improve material characteristics.Overall, the comprehension and control of precipitate formation plays an essential part in providing the strength and reliability of welded materials.
During welding, some stainless steels can produce secondary austenite.In steel's microstructure, it creates a secondary phase as shown in figure 12(c).Secondary austenite forms in high-temperature areas like a welded joint's HAZ.The chemical composition and mechanical characteristics of secondary austenite might vary from those of primary austenite, affecting steel properties.Intergranular corrosion may occur at steel grain boundaries due to this subsequent phase.According to Pires et al [52], welding or heat treatment must be carefully regulated to reduce secondary austenite and create a constant microstructure across the steel to prevent this sort of corrosion.Sample No. 5 has the highest Fe concentration, which may increase strength, magnetic characteristics, thermal conductivity, and manufacturing.Sample No. 5 has more iron, which improves mechanical characteristics, magnetizability, heat transfer, and manufacturing workability.Sample No. 5's higher chromium concentration may improve corrosion, oxidation, wear, high-temperature strength, and aesthetics.Chromium makes the material resistant to corrosion, oxidation, wear, and high temperatures, and appealing.Sample No. 4 exhibits the highest nickel content, which contributes to increased strength, improved crack resistance, and corrosion resistance.Sample No.6 exhibits better mechanical properties, characterized by a moderate chromium content of 17.64% and a predominant Fe content of 68.69%.Additionally, it demonstrates the highest oxygen content of 2.20%.However, it is worth noting that the elevated oxygen levels in this sample may lead to a greater occurrence of oxides than in other welding joints.According to the findings of Bansod et al [16], Chuaiphan and Srijaroenpramong [17], and Utu et al [53].

Taguchi analysis results
Process parameter sensitivity is often studied using the Taguchi technique.It uses the fewest experiments to do this.Experimentation often uses the Taguchi L9 configuration.The L9 orthogonal array is an experimental factor configuration.To study the effects of different mix ratios and gas types, trials are conducted in Samples [32].The Taguchi analysis results were conducted using the Minitab17 software.

UTS strength
ANOVA analysis demonstrated that the gas combination rate has the most effect among the three parameters (arc current, filler feed rate, and gas mixture) and has the greatest impact on UTS, with a contribution of 42.59%.Following that, the arc current and wire feed are rated at 15.15% and 32.35%, respectively, as shown in table 6.The S/N ratio rank determined the most desirable welding parameters for producing the best UTS have been determined as the arc current (160A), filler feed rate (4 m min −1 ), and gas mixture (G1), as determined by figures 13(a)-(d) and table 7 which display the appropriate values for each shielding gas content, arc current, and wire feed rate, it is evident that larger values are preferred.As reported in the study by Khrais et al [23].

Taguchi analysis of EL%
ANOVA analysis demonstrated that the gas combination rate has the most effect among the three parameters (arc current, filler feed rate, and gas mixture) and has the greatest impact on EL.%, with a contribution of 34.43%Following that, the arc current and wire feed are rated at 33.64% and 28.89%, respectively, as shown in table 8.The S/N ratio rank determined the most desirable welding parameters for producing the best EL% have been determined as the arc current (160A), filler feed rate (4 m min −1 ), and gas mixture (G1), as determined by figures 14(a)-(d) and table 9 which display the appropriate values for each shielding gas content, arc current, and wire feed rate, it is evident that larger values are preferred.As reported in the study by Khrais et al [23].

Charpy impact test
ANOVA analysis demonstrated that the gas combination rate has the most effect among the three parameters (arc current, filler feed rate, and gas mixture) and has the greatest impact on AISI 316L/ER316L toughness, with a contribution of 38.89%Following that, the arc current and wire feed are rated at 37.54% and 21.01%, respectively, as shown in table 10.The S/N ratio rank determined the most desirable welding parameters for producing the best AISI 316L/ER316L toughness have been determined as the arc current (160A), filler feed rate (4 m min −1 ), and gas mixture (G1), as determined by figures 15(a)-(d) and table 11 which display the appropriate values for each shielding gas content, arc current, and wire feed rate, it is evident that larger values are preferred.As reported in the study by Khrais et al [23].ANOVA analysis demonstrated that the Gas combination has the most effect among the three parameters (arc current, filler feed rate, and gas mixture) and has the greatest impact on HAZ, with a contribution of 42.57%.Following that, the Wire feed and arc current are rated at 30.81% and 20.22%, respectively, as shown in table 14.The S/N ratio rank determined the most desirable welding parameters for producing the best HAZ have been determined as the arc current (120A), filler feed rate (3 m min −1 ), and gas mixture (G2), as determined by figures 17(a)-(d) and table 15 which display the appropriate values for each shielding gas content, arc current, and wire feed rate, it is evident that larger values are preferred.As reported in the study by Khrais et al [23].

Conclusion
The findings of this study reveal critical insights into the welding parameters for AISI 316L/ER316L, shedding light on the significance of gas combination, arc current, and filler feed rate.The gas combination emerges as the most influential factor across various aspects of welding performance.Notably, it exerts a substantial impact on the Ultimate Tensile Strength (UTS), Elongation (%EL), toughness, Fusion Zone (FZ), and Heat-Affected Zone (HAZ).
• For UTS, an optimal welding scenario of 160A arc current, 4m/min wire feed rate, and gas combination G1 yielded an impressive UTS of 515.77MPa.Similarly, the best combination for %EL was 160A, 4m/min wire feed rate, and G1, achieving 20.85%.The toughness of AISI 316L/ER316L was maximized at 160A, 4m/min wire feed rate, and G1, resulting in a toughness value of 133J.
• In terms of FZ, gas combination G3, coupled with 120A arc current and 3m/min filler feed rate, yielded the most desirable hardness of 253.79 VH.Furthermore, for HAZ, the same gas combination (G3) alongside 120A arc current and 3m/min filler feed rate produced an optimal hardness value of 239.68 VH, emphasizing the pivotal role of gas combination in this context.
• The microstructure analysis, increasing the wire feed rate leads to greater deposition of metal, resulting in a larger welding pool and elevated heat input.This, in turn, facilitates more extensive mixing and diffusion between the molten metal in the weld zone and the base metal, ultimately yielding a more uniform microstructure throughout the welded joint.
• The narrower Heat-Affected Zone (HAZ) observed can be attributed to the heightened heat input rate and accelerated cooling during the welding process.Notably, a wire feed rate of 4 m/min yielded the smallest HAZ size, ranging from 2.924-7.047μm.At this wire feed rate, there was an increased tendency to form deltaferrite, which, in turn, resulted in the formation of a finer grain size of ferrite, ultimately enhancing mechanical properties.These findings underscore the pivotal role of wire feed rate in shaping welding outcomes and microstructure.
These findings underline the significance of gas combination and the interplay of welding parameters in optimizing the performance of AISI 316L/ER316L welding processes.These insights offer valuable guidance for practitioners and researchers in the field, fostering improved welding outcomes and product quality.

Figure 2 .
Figure 2. The experimental setup and the presence of gas cylinders.

2. 6 . 1 .
Exploring material properties: unveiling the secrets of tensile strength, charpy impact, and vickers hardness tests In the materials testing, three techniques stand out: the Tensile Strength Test, the Charpy Impact Test (CIT), and the Vickers Hardness Test (HV).

Figure 7 .
Figure 7.Samples after charpy test of batch.

Figure 12 .
Figure 12.The SEM and EDS images of FZ of (a) sample No.4 (b) sample No. 5 (c) sample No. 6.

Figure 13 .
Figure 13.The effect of MIG/MAG parameters plot on UTS (a) the impact of Ar (b) the impact of He (c) the impact of CO 2 (d) The impact of N 2 .

Figure 14 .
Figure 14.The effect of MIG/MAG parameters plot on EL%(a) the impact of Ar (b) the impact of He (c) the impact of CO 2 (d) The impact of N 2 .

Figure 16 .
Figure 16.The effect of MIG/MAG parameters plot on FZ (a) the impact of Ar (b) the impact of He (c) the impact of CO 2 (d) The impact of N 2 .

Figure 17 .
Figure 17.The effect of MIG parameters plot on HAZ (a) the impact of Ar (b) the impact of he (c) the impact of CO 2 (d) the impact of N 2 .

Table 3 .
Setup of welding parameters by taguchi L9 orthogonal array.

Table 4 .
[28]AISI 316L /ER 316L mechanical properties results.Moreover, wire feed rates and arc currents dictate heat input, impacting UTS and EL%.Increased ER 316L feed rates and shielding gas group of G1 accelerate the process, potentially decreasing HAZ and enhancing UTS.However, excessive rates with shielding gas groups of G2 or G3 might compromise fusion or cause overpenetration, affecting weld strength.Conversely, higher arc currents expand HAZ, necessitating a balance between the arc current and the feed rate of the wire.Because high heat input can lead to deformations, decreasing UTS.Furthermore, shielding gases of G1 such as Ar (60.67 vol%) and He (23.33 vol%) promote penetration and shielding, increasing UTS.Conversely, the shielding gas of G3 CO 2 (2.63 vol%) and N 2 (11.4 vol%) can induce spatter and porosity, weakening welds.As reported by Srivastava and Garg[28], Mortazavi et al seen in Sample No. 1, 4, 6, and 9, due to higher heat input resulting in more complete fusion.Increasing both the wire feed rate and arc current generally resulted in higher UTS values.However, at a certain point, increasing the wire feed rate may not result in a significant UTS decrease which may result in improper fusion and porosity formation.

Table 6 .
ANOVA table of UTS.

Table 7 .
Taguchi analysis: UTS versus arc current, wire feed rate, shielding gas combination.
[23]ent, filler feed rate, and gas mixture) and has the greatest impact on FZ, with a contribution of 48.27%.Following that, the Wire feed and arc current are rated at 24.98% and 22.17%, respectively, as shown in table 12.The S/N ratio rank determined the most desirable welding parameters for producing the best FZ have been determined as the arc current (120A), filler feed rate (3 m min −1 ), and gas mixture (G2), as determined by figures 16(a)-(d) and table 13 which display the appropriate values for each shielding gas content, arc current, and wire feed rate, it is evident that larger values are preferred.As reported in the study by Khrais et al[23].

Table 9 .
Taguchi analysis: El% versus arc current, wire feed rate, shielding gas combination.The effect of MIG/MAG parameters plot on toughness the impact of AR (b) the impact of he (c) the impact of CO 2 (d) the impact of N 2 .

Table 11 .
Taguchi analysis: impact energy versus arc current, wire feed rate, shielding gas combination.

Table 10 .
ANOVA table of charpy impact test.

Table 13 .
Taguchi analysis: FZ versus arc current, wire feed rate, shielding gas combination.

Table 12 .
ANOVA table of FZ hardness.

Table 14 .
ANOVA table of HAZ hardness.