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In the present research, the influence of friction stir welding (FSW) tool material on the mechanical and microstructural properties of friction stir (FS) welded 316L stainless steel butt joints is investigated. FS welds were produced using two different tungsten based FSW tools having identical tool shoulder and pin profiles. In both the cases, the FSW experimental runs were carried out using tool rotational speed of 600 rpm, welding speed of 45 mm/min, axial force of 11 kN and tool tilt angle of 1.5°. The results of the study show that the joints produced using the tungsten lanthanum oxide tool are having superior mechanical and microstructural properties when compared to the joints produced using tungsten heavy alloy tool. Furthermore, the tool degradation study by mass loss and photographic techniques suggests that the tungsten lanthanum oxide tool is more prone to degradation by plastic deformation, whereas the tungsten heavy alloy tool is more prone to degradation by wear.

The requirement of weight reduction, high thermal conductivity and strength at low temperatures and high corrosion resistance has identified the use of Al alloys together with steel in various fields. The use of Al alloys together with steel warrants efficient joining of Al alloys with steels. Friction stir welding (FSW) is a potential candidate for the joining of difficult-to-weld similar and dissimilar materials due to its inherent advantages as a solid state joining process. In order to speed up the research activities that lead to industrial level implementation of FSW of dissimilar Al alloys and steels, modelling and simulation can play a vital role. In this work, a central composite-response surface method (RSM) model is developed to predict the ultimate tensile strength (UTS) of friction stir-welded dissimilar Al alloy AA5052 H32 and HSLA steel IRS M-42-97. The adequacy of the model is verified by the analysis of variance (ANOVA) and computed values of the actual and adjusted R 2 values. The model is validated by the results of experimental trials at parameter combination other than that experimented as per the DOE matrix and found in agreement with an average error of −0.34 %. From the analysis of the developed model, it is observed that the UTS of the joint is very sensitive to the primary FSW parameters, and, as such, the range of primary FSW parameters that could produce significant joint strength is very narrow. Also, it is observed that the tool rotational speed, welding speed and axial force have a significant interaction effect on the UTS of the joint. The analysis of the model and discussion on the effect of FSW parameters on the tensile strength of the joint are supported by the results of scanning electron microscopy and EDS analysis at the joint interface of selected joints.

Friction stir welding provides an alternative method of joining aluminum in a reliable way. Anticipation of the joint efficiency is then a necessary step to optimize the process of the welding operation. In the light of this, artificial neural network (ANN) technique may then be applied as a reliable method for simulating and predicting the durability of the joints for different process parameters. In the present work, an ANN model is presented that predicts the ultimate tensile strength of friction stir-welded dissimilar aluminum alloy joints. Four parameters were considered including tool pin profile (straight square, tapered square, straight hexagon, straight octagon and tapered octagon), rotational speed, welding speed and axial force. Experimental tests were conducted according to a four-parameter five level central composite design. A feed-forward back propagation ANN with a single hidden layer comprising 20 neurons was employed to simulate the ultimate tensile strength (UTS) of the joints. The neural network was trained using the data obtained from the experimental work. A comparison between the experimental and simulated data showed that the ANN model reliably predicted the UTS of dissimilar aluminum alloy friction stir-welded joints. The models developed were capable of predicting values with less than 5 % error. Furthermore, the effect of different process parameters on the tensile behavior of dissimilar joints was also investigated and reported upon.

In the present work 3 mm thick aluminium alloy AA5052 and HSLA steel were successfully butt joined using friction stir welding (FSW) technique. The FSW trials were carried out by varying the tool traverse speed while keeping the other parameters constant. The joint characteristics such as ultimate tensile strength (UTS), microhardness, microstructure at the joint interface and fracture surface of fractured tensile specimens were investigated. SEM and EDS analysis suggest that in all cases intermetallic compound (IMC) layer is formed at the joint interface and its thickness is critical in the tensile strength of the joint. For a given tool rotational speed, axial load and tool tilt angle, the tool traverse speed has significant influence on the thickness of IMC layer formed and hence on the joint strength. The highest joint strength of about 91% of UTS of the base aluminium alloy is obtained at tool traverse speed of 45 mm/min and the UTS follow approximately a centre peak type variation against tool traverse speed.

In the preset investigation, aluminum alloy, AA5052 and HSLA steel are successfully butt welded using a modified FSW process wherein the work pieces submerged in a liquid medium are stirred by the FSW tool. The trials are conducted by varying the tool rotational speed from 400 rpm to 900 rpm while keeping the other parameters constant. The welded joints are tested for ultimate tensile strength (UTS) and the joint interface microstructure is analyzed using SEM and EDS. The results show that when compared to the normal FSW process, the peak value of UTS is marginally low but the range of tool rotational speed that could produce defect free joints with good joint strength is almost doubled in the modified FSW process.

The present investigation is carried out to investigate on mechanical and metallurgical properties of Friction stir (FS) / Underwater Friction stir (UFS) welded 3 mm thick AISI 316 L stainless steel joints. Experiments were carried out at a tool rotational speed of 700 rpm, welding speed of 45 mm/min and axial force of 12 kN. Defect free joints were confirmed by visual inspection. A marginal rise of about 4.5 % increase in the joint strength is achieved in water cooling than by gas cooling technique. Reduced peak temperature in water cooled joint led to better grain refinement in the weld nugget enhancing FSW tool life. No sign of secondary phase precipitation was observed in the weld joints which was confirmed by Energy Dispersive Spectroscopy (EDS) spectrums and micro etchants like Groesbeck and modified Murakami reagents in the weld nugget.

In the present work, the effect of tool axis offset from the joint interface and geometry of the FSW tool pin on the mechanical and metallographic characteristics of dissimilar friction stir butt welded aluminum (Al) alloy, AA5052 H32 and HSLA steel, IRSM42-93 were investigated. FSW tools having fixed shoulder diameter, pin tip diameter and pin length with three different tapered cylindrical (TC) and one straight cylindrical (SC) tool pin profiles were experimented. The constant FSW parameters used were: tool rotational speed of 500 rpm, welding speed of 45 mm/min, axial load of 7 kN and tool tilt angle of 1.5°. The effect of tool axis offset was investigated by continuously changing the tool axis offset by keeping the tool traverse direction at an angle to the joint interface. The ultimate tensile strength (UTS) of the joint is considered as the main criterion of the joint performance. The results show that the TC pin profile is beneficial and for a given FSW tool geometry and parameters, the taper angle of the tool pin and volume of tool pin penetration into steel side have significant influence on the thickness and composition of the intermetallic compound (IMC) layer formed and hence the joint performance. FSW tool having TC pin with 10° taper angle has produced the best joint at a tool axis offset of 2 mm towards the Al alloy. For the experimented tool pin geometries, the IMC layer formed at the joint interface is consistent with FeAl, Fe2Al5 and FeAl3.

Aluminium Matrix Composites (AMCs) reinforced with particulate form of reinforcement has replaced monolithic alloys in many engineering industries due to its superior mechanical properties and tailorable thermal and electrical properties. As aluminium nitride (AlN) has high specific strength, high thermal conductivity, high electrical resistivity, low dielectric constant, low coefficient of thermal expansion and good compatibility with aluminium alloy, Al/AlN composite is extensively used in electronic packaging industries. Joining of AMCs is unavoidable in many engineering applications. Friction Stir Welding (FSW) is one of the most suitable welding process to weld the AMCs reinforced with particulate form of ceramics without deteriorating its superior mechanical properties. An attempt has been made to develop regression models to predict the Ultimate Tensile Strength (UTS) and Percent Elongation (PE) of the friction stir welded AA6061 matrix composite reinforced with aluminium nitride particles (AlN p ) by correlating the significant parameters such as tool rotational speed, welding speed, axial force and percentage of AlN p reinforcement in the AA6061 matrix. Statistical software SYSTAT 12 and statistical tools such as analysis of variance (ANOVA) and student’s t test, have been used to validate the developed models. It was observed from the investigation that these factors independently influenced the UTS and PE of the friction stir welded composite joints. The developed regression models were optimized to maximize UTS of friction stir welded AA6061/AlN p composite joints.

Development of welding procedures to join aluminum matrix composite (AMCs) holds the key to replace conventional aluminum alloys in many applications. In this research work, AA6061/B4C AMC was produced using stir casting route with the aid of K2TiF6 flux. Plates of 6 mm thickness were prepared from the castings and successfully butt joined using friction stir welding (FSW). The FSW was carried out using a tool rotational speed of 1000 rpm, welding speed of 80 mm/min and axial force of 10 kN. A tool made of high carbon high chromium steel with square pin profile was used. The microstructure of the welded joint was characterized using optical and scanning electron microscopy. The welded joint showed the presence of four zones typically observed in FSW of aluminum alloys. The weld zone showed fine grains and homogeneous distribution of B4C particles. A joint efficiency of 93.4% was realized under the experimental conditions. But, FSW reduced the ductility of the composite.

The microstructure and mechanical characterization of dissimilar friction stir welded AA5083-H111 and AA6351-T6 aluminum alloys were studied. Three different welding speeds (36, 63 and 90 mm/min) were used to weld the dissimilar alloys. The effect of welding speed on mechanical and metallurgical properties was analyzed. It is found that the welding speed of 63 mm/min produces better mechanical and metallurgical properties than other welding speeds. The weld zone is composed of three kinds of microstructures, namely unmixed region, mechanically mixed region and mixed flow region. The fracture mode was observed to be a ductile fibrous fracture.

Aluminium alloys generally present low weldability by traditional fusion welding process. Development of the friction stir welding (FSW) has provided an alternative improved way of producing aluminium joints in a faster and reliable manner. The quality of a weld joint is stalwartly influenced by process parameter used during welding. An approach to develop a mathematical model was studied for predicting and optimizing the process parameters of dissimilar aluminum alloy (AA6351 T6-AA5083 H111) joints by incorporating the FSW process parameters such as tool pin profile, tool rotational speed welding speed and axial force. The effects of the FSW process parameters on the ultimate tensile strength (UTS) of friction welded dissimilar joints were discussed. Optimization was carried out to maximize the UTS using response surface methodology (RSM) and the identified optimum FSW welding parameters were reported.

Over the last two decades, aluminium matrix composites (AMCs) reinforced with particulate form of ceramics have attracted much attention due to their superior mechanical properties. In recent years, friction stir welding (FSW) is largely employed to successfully join the AMCs reinforced with ceramic particulates. An attempt has been made to develop a regression model to predict the ultimate tensile strength (UTS) of the friction stir (FS) welded AA6061 matrix composite reinforced with aluminium nitride particles (AlNp) by incorporating significant parameters such as tool rotational speed, welding speed, axial force and percentage of AlNp reinforcement in the matrix. A four factor, five level central composite rotatable design has been used to minimize the number of experimental runs. The effects of those factors on UTS of the welded joints have been analyzed using the developed regression model. The developed regression model has been validated by statistical software SYSTAT 12 and statistical tools such as analysis of variance (ANOVA) and student’s t test. It was found that the model was accurate. The developed regression model can be effectively used to predict the UTS of FS welded joints at 95% confidence level. It was observed from the investigation that factors considered in this study independently influenced the UTS of the FS welded composite joints.

The relatively new welding process friction stir welding (FSW) was applied in this research work to join 6 mm thick dissimilar aluminum alloys AA5083-H111 and AA6351-T6. The effect of tool rotational speed and pin profile on the microstructure and tensile strength of the joints were studied. Dissimilar joints were made using three different tool rotational speeds of 600 rpm, 950 rpm and 1300 rpm and five different tool pin profiles of straight square (SS), straight hexagon (SH), straight octagon (SO), tapered square (TS), and tapered octagon (TO). Three different regions namely unmixed region, mechanically mixed region and mixed flow region were observed in the weld zone. The tool rotational speed and pin profile considerably influenced the microstructure and tensile strength of the joints. The joint which was fabricated using tool rotational speed of 950 rpm and straight square pin profile yielded highest tensile strength of 273 MPa. The two process parameters affected the joint strength due to variations in material flow behavior, loss of cold work in the HAZ of AA5083 side, dissolution and over aging of precipitates of AA6351 side and formation of macroscopic defects in the weld zone.

Inadequate development of fabrication methods restricts the applications of new families of aluminum matrix composites (AMCs). Friction stir welding (FSW) is a potential candidate to join AMCs without any defects associated with conventional fusion welding processes. The primary objective of the present work is to apply FSW process to join AA6061/(0, 5 and 10 wt.%) ZrB 2 in situ cast composites and evaluate the joint properties. The composites were prepared by reacting inorganic salts K 2 ZrF 6 and KBF 4 with molten aluminum and joined using a FSW machine at a tool rotational speed of 1150 rpm, welding speed of 50 mm/min and axial force of 6 kN. The joints showed the presence of various zones such as weld zone (WZ), thermomechanically affected zone (TMAZ) and heat affected zone (HAZ). The weld zone was characterized with a homogenous distribution of ZrB 2 particles. The stirring action of the tool resulted in fragmentation of several clusters present in the parent composite. The weld zone exhibited higher hardness than that of the parent composite. The tensile strength of welded joints was comparable to that of parent composites. The wear resistance of the composites improved subsequent to FSW.

New families of aluminum matrix composites (AMCs) have been developed over the last decade in search of superior properties. Aluminum reinforced with ZrB2 particles is one such family which has drawn the attention of researchers. Friction stir welding is a relatively new solid state welding which overcomes most of the defects associated with fusion welding of AMCs. An attempt has been made to friction stir weld AA6061/0–10 wt% ZrB2 in situ composite and to develop an empirical relationship to predict the tensile strength of butt joints. Four factors, five levels central composite rotatable design was used to minimize the number of experiments. The factors considered are tool rotational speed, welding speed, axial force and weight percentage of ZrB2. The effect of these factors on tensile strength of the welded joints is analyzed using the developed empirical relationship. The predicted trends are discussed. It is observed that the factors independently influence the tensile strength over the entire range of parameters studied in this work.

PurposeThe SiC reinforced Al composite is perhaps the most successful class of metal matrix composites (MMCs) produced to date. They have found widespread application for aerospace, energy, and military purposes, as well as in other industries – for example, they have been used in electronic packaging, aerospace structures, aircraft and internal combustion engine components, and a variety of recreational products. In all these applications, welding plays a vital role. Little attention has been paid to SiC reinforced aluminium matrix composites joined by gas tungsten arc (GTA) welding. The purpose of this paper is to outline the manufacturing method for producing MMCs, GTA welding of MMCs and pitting corrosion analysis of welded MMCs.Design/methodology/approachThis paper focuses upon production and welding of metal matrix composites. The welded composites have been treated at elevated and cryogenic temperatures for experimental studies. Pitting corrosion analysis of welded plates was carried out as per Box Benkehn Design.FindingsFrom the results, it should be noted that maximum pitting resistance was observed with MMCs containing 10% SiC treated at cryogenic temperature. Corrosion resistance of welded composites treated at elevated temperature was found to be higher than that of as‐welded and at cryogenic temperature treated composites. The pitting potential increases with increase in % SiC to certain level and decreases with further increase in % SiC. Corrosion potential of composites treated at elevated temperature is high compared to other composites. Maximum pitting resistance is observed when the welding current was kept at 175 amps for 10% addition of SiC in LM25 matrix treated at cryogenic temperature.Originality/valueThe paper outlines the manufacturing method for producing MMCs, GTA welding of MMCs and pitting corrosion analysis of welded MMCs. The results obtained may be helpful for the automobile and aerospace industries.

A variety of ceramic particles is added to aluminum alloys to produce aluminum matrix composites (AMCs). Establishing the joining procedure for AMCs is an essential requirement prior to extending their applications. Friction stir welding (FSW) is an emerging solid state welding which eliminates all the defects associated with fusion welding of AMCs. An attempt has been made to friction stir weld AA6061/ ZrB2 in-situ composite. A four factor, five level central composite rotatable design has been used to minimize the number of experiments. The four factors considered are tool rotational speed, welding speed, axial force and weight percentage of ZrB2. A mathematical model has been developed incorporating the FSW process parameters to predict the ultimate tensile strength (UTS) and FS process is optimized using generalized reduced gradient method (GRG) to maximize the UTS. The effect of process parameters on UTS was analyzed. It was observed that the process parameters independently influence the UTS over the entire range studied in this work.

Now a days Friction stir Welding (FSW) has become very popular for joining of aluminium alloys and aluminium based composites. FSW produced the effective joints on the Metal matrix composites (MMCs) without defects like porosity, interfacial chemical reactions, reinforcement segregation etc., The desired mechanical properties of the weld can be achieved, depends on the FSW parameters such as rotational speed (N), welding speed (S), axial force (F) and the reinforcement content (%R) in the MMCs. In this study, a mathematical model was developed to predict the tensile strength friction stir welded Al/B4C joints using SYSTAT software. The central composite design of four factors and five levels has been used to conduct the experiments. The optimal process parameters were estimated from the developed regression equation using Generalized Reduced Gradient (GRG) method.

The objective of this research work is to identify a set of friction stir welding parameters to join aluminum matrix composites which will give higher tensile strength, ductility and wear resistance. AA6061/ZrB2 composites were produced by the in situ reaction of K2ZrF6 and KBF4 with molten aluminum. Plates of 6 mm thickness were prepared from castings and joined using friction stir welding. Four factors, five levels central composite rotatable design was used to minimize the number of experiments. The factors considered were tool rotational speed, welding speed, axial force and weight percentage of ZrB2. Mathematical models were developed to predict tensile strength, elongation and wear rate. The developed mathematical models were optimized using generalized reduced gradient method to obtain higher tensile strength, ductility and wear resistance. The optimized parameters can be fed into the friction stir welding machine to automate the process to achieve desirable joint properties.

Aluminum alloys generally present low weldability by traditional fusion welding process. Development of Friction Stir Welding (FSW) has provided an alternative improved way of producing aluminum joints, in a faster and reliable manner. The quality of a weld joint is stalwartly influenced by process parameters used during welding. In this paper an attempt has been made to develop an empirical relationship between FSW process parameters to predict wear resistance of friction stir welded dissimilar aluminum alloys. Four factors, five levels central composite rotatable design has been used to minimize the number of experiments. The FSW parameter considered for experiments are tool pin profile, tool rotational speed, welding speed and axial force. Analysis of variance (ANOVA) technique has been used to check the adequacy of the developed model. The effect of these FSW parameters on wear resistance of the welded joints has been analyzed and the predicted trends are discussed. The FSW process parameters are optimized using Response Surface Methodology (RSM) to maximize the wear resistance. The optimum FSW welding parameters have been identified to maximize the wear resistance.

The bead parameters play a vital role in determining and understanding the properties of the weld cladding in fusion welding process. This investigation aims at minimizing weld dilution and predict...

The usage of particulate reinforced metal matrix composite (MMC) is steadily increasing due to its properties such as high specific strength, high specific modulus and good wear resistance. Aluminium matrix composite (AMC) plays an important role to meet the above requirements. Effective utilization of AMC is based on not only its production but also on fabrication methods. Among AMCs, those based on particulate reinforcements are particularly attractive, due to their lower production costs. Aluminium matrix titanium carbide reinforced composite (Al–TiC p ) was produced in an inert atmosphere by indigenously developed Modified Stir Casting Process with bottom pouring arrangement (3–7% TiC by weight). Friction stir welding process (FSW) is employed to make weld joints. The welding parameters such as axial force, welding speed, tool rotational speed, percentage TiC addition etc., and profile of the tool were considered for analysis. In this study, an attempt is made to predict ultimate tensile strength (UTS) of the welded joints using a mathematical model. The FSW specimens without any post-weld heat treatment belonging to a different set of parameters tested, exhibited a high joint efficiency (most of them ranging from 90% to 98%) with respect to the ultimate tensile strength of the base material AA6061. It was found from the analysis of the model that the tool pin profile and the welding speed have more significant effect on tensile strength.

The heat treatable aluminium alloy AA2024 is used extensively in the aircraft industry because of its high strength to weight ratio and good ductility. The non-heat treatable aluminium alloy AA5083 possesses medium strength and high ductility and used typically in structural applications, marine, and automotive industries. When compared to fusion welding processes, friction stir welding (FSW) process is an emerging solid state joining process which is best suitable for joining these alloys. The friction stir welding parameters such as tool pin profile, tool rotational speed, welding speed, and tool axial force influence the mechanical properties of the FS welded joints significantly. Dissimilar FS welded joints are fabricated using five different tool pin profiles. Central composite design with four parameters, five levels, and 31 runs is used to conduct the experiments and response surface method (RSM) is employed to develop the model. Mathematical regression models are developed to predict the ultimate tensile strength (UTS) and tensile elongation (TE) of the dissimilar friction stir welded joints of aluminium alloys 2024-T6 and 5083-H321, and they are validated. The effects of the above process parameters and tool pin profile on tensile strength and tensile elongation of dissimilar friction stir welded joints are analysed in detail. Joints fabricated using Tapered Hexagon tool pin profile have the highest tensile strength and tensile elongation, whereas the Straight Cylinder tool pin profile have the lowest tensile strength and tensile elongation. The results are useful to have a better understanding of the effects of process parameters, to fabricate the joints with desired tensile properties, and to automate the FS welding process.

In the present work, Al–10 wt.% TiB2 metal matrix composites (MMCs) are joined using friction stir welding (FSW) process. Different tool pin profiles are developed to weld the MMCs and the effect of tool pin profile on metallurgical and mechanical properties of the weldments are studied. The stirred zones of MMCs joined with taper pin profiles are narrower than that are joined with straight pin profiles. Weld nugget has finer grains compared to other weld zones and TiB2 particulates are homogeneously present in Al matrix both in weld and parent metal. The effect of pin profiles on mechanical properties are analyzed and it is found that joints welded with straight square pin profile have better mechanical properties compared to the other pin profiles.

A three-dimensional transient thermo-mechanical simulation has been performed on a welded Tee-joint using the finite element method, to predict longitudinal residual stresses. The uncoupled thermo-mechanical simulation consists of two stages. The first stage involves the prediction of the complete thermal history of the weldment. The second stage involves the thermo-mechanical simulation on the basis of the results of the first stage. Temperature dependent thermal and mechanical properties were incorporated in the simulation. A relatively new contour method was used to experimentally validate the longitudinal residual stresses obtained by the thermo-mechanical simulation. The experimental results agree well with the simulated results of residual stresses.

Measurement of delta ferrite in cladding gives important insight into the future mechanical and corrosion resistant behaviour of the cladded structures. The amount of delta ferrite formed during cladding is influenced by process parameters such as welding speed, welding current, and nozzle-to-plate distance. Therefore, it is essential to predict the effect of these parameters on the formation of delta ferrite. This article discusses the development of an artificial neural network model to predict the delta ferrite content in austenitic stainless-steel claddings deposited by the flux cored arc welding process. A novel approach of using the design of experiments to collect data to train the network has been adopted in this investigation. The study revealed that the delta ferrite content can be predicted more accurately using the neural networks with a minimum number of experiments. The results also indicated that welding current and speed have a significant influence on the amount of ferrite and the interaction effects of these parameters play a major role in determining ferrite in the claddings.

Plasma transferred arc hardfacing has attracted increasing attention for its effective protection against corrosion, thermal shock, and abrasion. The quality of hardfaced components depends on the weld bead geometry and dilution, which have to be properly controlled and optimized to ensure better economy and desirable mechanical characteristics of the weld. These objectives can be fulfilled by developing mathematical equations to predict the dimensions of the weld bead. This paper highlights the development of such mathematical equations using multiple regression analysis, correlating various process parameters to weld bead geometry in PTA hardfacing of Colmonoy 5, a nickel-based alloy over stainless steel 316 L plates. The experiments were conducted based on a five factor, five level central composite rotatable design matrix. A genetic algorithm (GA) was developed to optimize the process parameters for achieving the desired bead geometry variables.

Optimization of pulsed gas tungsten arc welding (pulsed GTAW) process parameters was carried out to obtain optimum weld bead geometry with full penetration in welding of stainless steel (304L) sheets of 3 mm thickness. Autogenuous welding with square butt joint was employed. Design of experiments based on central composite rotatable design was employed for the development of a mathematical model correlating the important controllable pulsed GTAW process parameters like pulse current (Ip), pulse current duration (Tp), and welding speed (S) with weld bead parameters such as penetration, bead width (W), aspect ratio (AR), and weld bead area of the weld. The developed models were checked for adequacy based on ANOVA analysis and accuracy of prediction by conducting a confirmation test. Weld bead parameters predicted by the models were found to confirm observed values with high accuracy. Using these models, the main and interaction effects of pulsed GTAW process parameters on weld bead parameters were studied and discussed. Optimization of pulsed GTAW process parameters was carried out to obtain optimum bead geometry using the developed models. A quasi-Newton numerical optimization technique was used to solve the optimization problem and the results of the optimization are presented.

Most engineering applications require both high strength and corrosion resistant materials for long reliability and performance. This can be achieved by cladding the surface of steel with a metallurgically compatible corrosion resistant alloy. In recent years, duplex stainless steel has been extensively used for weld cladding. It has excellent pitting and crevice corrosion resistance, high yield strength, good toughness and weldability. During cladding, pitting resistance may be compromised by the formation of intermetallic precipitates, or by excessive precipitation of secondary austenite in the surface regions. Redistribution of alloying elements as a result of such transformations may lead to local reductions in pitting resistance. This may result from the dilution of the filler metal with the base metal and the heat input during cladding. Hence, control of dilution and heat input is very important to maintain the required pitting corrosion resistance. The present paper highlights an experimental study and analysis of various welding parameters influencing PREN and pitting potential in duplex stainless steel cladding deposited by flux cored arc welding (FCAW). Pitting resistance equivalent number (PREN) was found to decrease with increased welding current and welding speed and to increase with increased welding angle and tip to workpiece distance. Pitting potential increased with increased welding current, and tip to workpiece distance and heat input during cladding, and decreased with increased welding speed and welding angle.

Pulsed welding is a controlled method of spray transfer, in which the arc current is maintained at a value high enough to permit spray transfer and for long enough to initiate detachment of a molten droplet. Once the droplet is transferred the current is reduced to a relatively low value to maintain the arc. These periods of low current allow the average arc current to be reduced into the range suitable for positional welding, while periodic injection of high current pulses allows metal to be transferred in the spray mode. Parameters of these current pulses, such as Ip Ib, Tp and Tb have a distinct effect on the characteristics viz., the stability of the arc, weld quality, bead appearance and weld bead geometry. Improper selection of these pulse parameters may cause weld defects including irregular bead surface, lack of fusion, undercuts, burn-backs and stubbing-in. Therefore, it is important to select a proper combination of parameters of the pulsed current for welding, which will ensure that the process gives proper results in all the above aspects. However, arriving at such a combination of parameters without a rational base would be only a matter of chance with a fairly low probability for achieving desirable weld properties, since the complexity and interdependence of pulse parameters involved in this process. These difficulties of setting-up the welding conditions correctly has been one of the main reasons for the lack of popularity of pulsed GMA welding in industries. Hence, a detailed study is essential to arrive at a method of predicting the conditions that will give a good weld and this paper reviews various aspects of the pulsed GMA welding, the effects of pulse parameters and different methodologies adopted for selecting these parameters to obtain better quality welds.

Austenitic stainless steel cladding is generally used to attain better corrosion resistance properties to meet the requirements of petrochemical, marine, and nuclear applications. The quality of cladded components depends on the weld bead geometry and dilution, which in turn are controlled by the process parameters. In this investigation, the effect of cladding parameters such as welding current, welding speed, and nozzle-to-plate distance on the weld bead geometry was evaluated. The objective of controlling the weld bead geometry can easily be achieved by developing equations to predict these weld bead dimensions in terms of the process parameters. Mathematical equations were developed by using the data obtained by conducting three-factor five-level factorial experiments. The experiments were conducted for 317L flux cored stainless steel wire of size 1.2 mm diameter with IS:2062 structural steel as a base plate. Sensitivity analysis was performed to identify the process parameters exerting the most influence on the bead geometry and to know the parameters that must be most carefully controlled. Studies reveal that a change in process parameters affects the bead width, dilution, area of penetration, and coefficient of internal shape more strongly than it affects the penetration, reinforcement, and coefficient of external shape.

To automate a welding process, which is the present trend in fabrication industry, it is essential that mathematical models have to be developed to relate the process variables to the weld bead parameters. Because of its high reliability, deep penetration, smooth finish and high productivity, submerged arc welding (SAW) has become a natural choice in industries for fabrication, especially for welding of pipes. Mathematical models have been developed for SAW of pipes using five level factorial techniques to predict three critical dimensions of the weld bead geometry and shape relationships. The models developed have been checked for their adequacy and significance by using the F -test and the t -test, respectively. Main and interaction effects of the process variables on bead geometry and shape factors are presented in graphical form and using which not only the prediction of important weld bead dimensions and shape relationships but also the controlling of the weld bead quality by selecting appropriate process parameter values are possible.

The quality of a weld joint is strongly influenced by process parameters used during the welding. In order to have high quality welds, mathematical models that can predict the weld bead geometry and shape relationships have to be developed to accomplish the desired mechanical properties of the welding. This paper focuses on the development of mathematical models using response surface methodology (RSM) for the selection of process parameters and the prediction of bead geometry (penetration, reinforcement, dilution, bead width and total area) in automatic PTA (plasma transferred arc) hardfacing. RSM facilitates the optimisation of process parameters. Five factors were incorporated into the regression model: arc current, welding speed, powder feed rate, oscillation frequency and torch standoff. A sensitivity analysis has been conducted to compare the relative impact of five process parameters on bead geometry in order to verify the measurement errors on the values of the uncertainty in estimated pa...

The effect of controllable process variables on the heat input and the area of the heat-affected zone (HAZ) for bead-on-plate and bead-on-joint welding were calculated and analyzed using mathematical models developed for the submerged arc welding of pipes (SAW). A comparative study of the area of the heat-effected zone between bead-on-plate and bead-on-joint welding was carried out. This comparative study reveals that the models developed for bead-on-plate for predicting weld bead qualities need further modification before applying to the actual joining of metals by welding. It is found that the area of the HAZ is greater for bead-on-plate than that for bead-on-joint and that the effects of SAW process variables on the area of the HAZ on plate is as same as that of the area of the HAZ on joint, and follows the same trend.

Response surface methodology (RSM) is a technique to determine and represent the cause and effect relationship between true mean responses and input control variables influencing the responses as a two or three dimensional hyper surface. Submerged arc welding (SAW) is used extensively in industry to join metals in the manufacture of pipes of different diameters and lengths. The main problem faced in the manufacture of pipes by the SAW process is the selection of the optimum combination of input variables for achieving the required qualities of weld. This problem can be solved by the development of mathematical models through effective and strategic planning and the execution of experiments by RSM. This paper highlights the use of RSM by designing a four-factor five-level central composite rotatable design matrix with full replication for planning, conduction, execution and development of mathematical models. These are useful not only for predicting the weld bead quality but also for selecting optimum process parameters for achieving the desired quality and process optimization.

Friction stir welding (FSW) is used to join metal matrix composites (MMCs) which are increasingly used as a structural material in aerospace, automotive, and marine systems. The welded zone of the composite offers a more homogeneous distribution of reinforcement particles with a fine recrystallized grain structure resulting in both enhanced mechanical and wear properties. In this paper, the dry sliding wear behavior of the stir zone of friction stir welded AA6O6I-B4C composite is presented. The relationships between the wear rate of MMCs and friction stir welding process parameters were established using a mathematical model. The developed regression model was optimized to minimize the wear rate using the generalized reduced gradient (GRG) method.

Development of the Friction Stir Welding (FSW) has provided an alternative improved way of producing aluminium joints, in a faster and reliable manner. This paper presents a systematic approach to develop a mathematical model for predicting the Ultimate Tensile Strength (UTS) of dissimilar aluminum alloy (AA6351 T6 - AA5083 H111) joints by incorporating the Friction Stir Welding (FSW) process parameter such as tool pin profile, tool rotational speed, welding speed, and axial force. The experiment was conducted based on four factors five level central composite rotatable deign with full replication technique. The Response Surface Method (RSM) was employed to develop the model. The developed model was validated using the statistical tool analysis of variance (ANOVA). Conformity tests were carried out to check the accuracy of the developed model. The effects of the FSW process parameters on ultimate tensile strength of friction welded dissimilar joints were discussed in detail. DOI: http://dx.doi.org/10.5755/j01.mech.18.5.2699

Automatic weld surfacing is being employed increasingly in the process and power industries. Because of its high reliability, all-position capability, ease of use, low cost and high productivity, GMAW has become a natural choice for automatic surfacing. With increasing use of GMAW in its automatic mode, there will be increased dependence on the use of equations to predict the dimensions of the weld bead. The development of such mathematical equations using a four-factor 5-level factorial technique to predict the geometry of the weld bead in the deposition of 316L stainless steel onto structural steel IS 2062 is presented. The models developed have been checked for their adequacy and significance by using the F -test and the t -test, respectively. Main and interaction effects of the control factors on dilution and bead geometry are presented in a graphical form that helps in selecting quickly the process parameters to achieve the desired quality of overlay.

Different weight percentage of B4C particulates reinforced Aluminum Matrix Composites (AMCs) are fabricated by modified stir casting route. The produced AMCs are Friction Stir Welded (FSW) using a four factor five level central composite design matrix. The dry sliding wear properties of nugget zone of the FSW composites were analysed using a pin-on-disc wear testing machine. The presence of B4C particulates and fine grain in the weld nugget improved the wear properties. The relationships between the wear rate of AMCs and friction stir welding process parameters were established using a regression model. The developed regression model was optimised to minimise the wear rate using the Generalised Reduced Gradient (GRG) method. The worn out surface characteristics of welded composites were studied using scanning electron microscopy. The numerous pits, grooves and wear tracks were observed in the microstructure.

Application of the Taguchi Orthogonal Array in conducting the experiments and for the optimisation of critical cladding process parameters for obtaining desirable delta ferrite content in the claddings is reported in this paper. Considering the application dependent requirement of the ferrite content on the performance of the cladded structures, two quality characteristics viz., Smaller-the-better, and Nominal-the-best were adopted for analysing the effect of process parameters on the formation of delta ferrite. The experimental results show that welding current has the most significant effect on the formation of delta ferrite.