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CHAPTER – 2
2.1 REVIEW OF LITERATURES
Sathya, et.al has expressed that, the friction weldment of austenitic stainless steel and optimizing the friction welding parameters in order to establish the weld quality. The processed joints were tested for their microstructure and strength related aspects. Also a method to decide near optimal settings of the process parameters using Genetic algorithm is proposed. Tensile tests showed that friction processed joints exhibited comparable strength with the base material and joint strength decreased with increase in friction time. The micro vicker′s hardness increases with increase in friction time. Genetic algorithm has been found useful in reducing the number of trials necessary to optimize conditions for friction welding of similar materials combination.
M.N.AhmadFauzi, et.al has concluded that, the interface of ceramic/metal alloy friction welded components is essential for understanding of the quality of bonding between two dissimilar materials. In the present study, optical and electron microscopy as well as four-point bending strength and microhardness measurements were used to evaluate the quality of bonding of alumina and 6061 aluminum alloy joints produced by friction welding. The joints were also examined with EDX (energy dispersive X-ray) in order to determine the phases formed during welding. The bonded alumina-6061 aluminum samples were produced by varying the rotational speed but keeping constant the friction pressure and friction time. It was also observed that rotational speed of 2500 rpm can produce a very good joint and microhardness with good microstructure as compared to the other experimental rotational speeds.
Mumin Sahin, et.al has experimentally stated that, an experimental friction welding setup, which is a continuous drive friction welding set-up, was used in the experiments. Firstly, optimum parameters were obtained to join parts having equal diameter. Secondly, the effects of welding parameters on welding strength were investigated. Later, the mechanical properties of joints were examined by using tensile tests, fatigue tests, notch-impact tests and hardness tests. The optimum parameters are friction time=5 s and friction pressure= 30 MPa. Upset time and upset pressure were kept constant at 20 s and 110 MPa. The tensile strengths of welded parts are about 95% of those of AISI 1040 parts, base metal. The fatigue strengths of welded parts are close to those of AISI 1040 parts, base metal. The notch-impact toughness is slightly bigger than that of AISI 1040 parts, base metal. As a result, welded parts can easily resist both static and dynamic loads.
O.torun, et.al has analysed that, friction welding of cast Fe-28Al alloy carried out for different times under constant friction pressure, forging pressure, forging time, rotational speeds. Shear strengths and hardness values of weld interface identified and microstructure properties of the welded samples were investigated by optical and scanning electron microscopy (SEM). According to the results of test, microhardness profiles for all welding times are found to be similar. Hardness of the recrystallized zone is higher than that of the base alloy due to formation of very fine grains. Microstructure studies revealed two different zones at the weld interface; recrystallized fully deformed zone and deformed zone. The micrographs clearly indicate a sound welding at the weld region which is free from pore and crack.
Mumin Sahin has conducted an experimental set-up to achieve the friction welding of components having equal diameter. The set-up was designed as continuous drive, and transition from friction to forging stage can be done automatically. In the experiments, high-speed steel (HSS—S 6-5-2) and medium-carbon steel (AISI 1040) were used. Post-weld annealing was applied to the joints at 650 ◦C for 4 h. First, the optimum welding parameters for the joints were obtained. Later, the strengths of the joints were determined by tension, fatigue and notch-impact tests, and results were compared with the tensile strengths of materials. Then, hardness variations and microstructures in the post-weld of the joints were obtained and examined. The tensile strength of the joints increases together with the friction time and pressure, and it raises a maximum, but it decreases for more friction time and pressure.
S.D. Meshram, et.al has expressed that, influence of interaction time in continuous drive friction welding on microstructure and tensile properties is studied. Increased interaction time led to decrease in strength in eutectoid forming and insoluble systems and improved strength in soluble systems. Mechanical transport of the material is predominant at the peripheral region of the weld. The influence of interaction time on microstructure and tensile properties of the friction welding of five dissimilar metal combinations, namely Fe–Ti, Cu–Ti, Fe–Cu, Fe–Ni and Cu–Ni system has been investigated. Extended interaction time led to decreased strength due to thicker intermetallic layer formation in eutectoid forming systems (Fe–Ti and Cu–Ti) and insoluble systems (Fe–Cu). In the soluble systems strength increment is observed with an increased interaction time due to solid solution formation.
R. Paventhan, et.al has attempted to develop an empirical relationship to predict the tensile strength of friction welded AA 6082 aluminium alloy and AISI 304 austenitic stainless steels joints, incorporating parameters such as friction pressure, friction time and forging time. Response surface methodology (RSM) was applied to optimizing the friction welding process parameters to attain the maximum tensile strength of the joint. An empirical relationship was developed to predict the tensile strength of friction welded AA6082 aluminium alloy and AISI 304 austenitic stainless steel dissimilar joints, incorporating process parameters. The developed relationship can be effectively used to predict the tensile strength of friction welded joints at a confidence level of 95%. A maximum tensile strength of 213 MPa could be attained under the welding conditions: 90 MPa of friction pressure, 90 MPa of forging force, 3 s of friction time, and 3 s of forging time.
Kunihiko Tsuchiya and Hiroshi Kawamura has conducted, the joining tests on Cu-I%Cr-I%Zr/SS316 by friction welding and optimum fabricating conditions of the Cu-alloy/SS316 joint. Additionally, the characteristics of tensile strength, hardness, metallographical observation and SEM/EPMA analyses on Cu-I%Cr-I%Zr/SS316 fabricated by friction welding were evaluated. Optimum conditions have been obtained from experiments for friction welding of Cu-Cr-Zr/SS316. Optimum conditions were a rotational speed of 2200 rpm under a friction pressure of 353 MPa. Upset pressure was 608 MPa and welding time was 2.0 s.
V.V. Sathyanarayana, et.al has expressed that, in continuous drive friction welding studies on austenitic–ferritic stainless steel combination sound welds are obtained at certain weld parameter combinations only. The mechanical properties of dissimilar metal welds are comparable to those of ferritic stainless steel welds. The mechanical properties of austenitic–ferritic stainless steel welds are similar to ferritic stainless steel welds. The toughness and strength properties of dissimilar metal welds are better than ferritic stainless steel parent metal. Notch tensile strength, hardness and impact toughness can be expressed in terms of the process parameters by regression equation obtained by statistical analysis.
Mumin Sahin et al has concluded that, austenitic-stainless steels are preferred over other stainless steels due greater ease in welding. In the present study, an experimental set-up was designed in order to achieve friction welding of plastically deformed austenitic-stainless steels. AISI 304 austenitic- stainless steels having equal and different diameters were welded under different process parameters. Strengths of the joints having equal diameter were determined by using a statistical approach as a result of tension tests. Hardness variations and microstructures using scanning electron microscope (SEM) analysis in the welding zone were obtained and examined. Maximum strength in the joints having equal diameters has about 96% that of base austenitic-stainless steel parts. Tensile strength decreases as the diameter ratio of the joints increases.
N. Ozdemir has expressed that, standard AISI 304L austenitic stainless steel and AISI 4340 steel couple were welded by friction welding process using five different rotational speeds. The joining performances of AISI 304L/AISI 4340 friction-welded joints were studied and the influences of rotational speed on the microstructure and mechanical properties of the welded joints were also estimate . The microstructural properties of heat affected zone (HAZ) were examined by scanning electron microscopy (SEM). The micro hardness across the interface perpendicular to the interface was measured and the strength of the joints was determined with tensile tests. The experimental results indicate that the tensile strength of friction-welded 304L/4340 components were markedly affected by joining rotational speed selected.
Emel Taban Jerry et.al has expressed that, inertia friction welding has been used to create joints between a 6061-T6 aluminium alloy and a AISI 1018 steel using various parameters. The joints were evaluated by mechanical testing and metallurgical analysis. Micro structural analyses were done using metallographic, micro hardness testing, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray elemental mapping, focused ion beam (FIB) with ultra high resolution SEM and transmission electron microscopy (TEM) in TEM and STEM modes. Results of these analyses first suggested that joint strengths on the order of 250 MPa could be achieved. In addition, fracture surfaces from these tests were characterized through SEM examination.
Mumin Sahin H and Erol Akata et.al, has designed and realised in order to achieve the friction welding of plastically deformed steel bars. The part shaving same and different diameters deformed plastically, but same material was welded with different process parameters. The strengths of the joints were determined by tension tests. Hardness variations and microstructures in the welding zone were obtained and the effects of welding parameters on the welding zone were investigated. The optimum welding parameters that obtained from equal diameter parts could not be used in welding of parts having different diameters and widths. Hardness in the horizontal direction of the joints increases at central zone. Hardness variation in vertical distance of the joints is almost equalled from the side to the centre of parts.
Andrej Ambrozia has expressed that, the friction welding of a dissimilar-metal joint in titanium and tungsten pseudo alloy, in which sintered tungsten grains and alloy Ni–Fe formed respectively the matrix (W-95 wt.%) and the bonding phase, was investigated. The aim of the investigations was to determine which microstructures occur in the titanium–tungsten pseudo alloy joint and which interlayer’s ensure that there are no brittle structures in it. The friction welding process was found to proceed differently than in the case of titanium–tungsten joints. Stable Ti–Fe–Ni–W intermetallic phases with cracks propagating in them would occur in the joint zone. Proper interlayer of copper on the tungsten pseudo alloy side and vanadium on the titanium side were selected. Joints with tensile strength of 410MPa were obtained.
Yuanzhi Zhu and Zhe Zhu et al has analysed that, the microstructure evolution in 4Cr10Si2Mo at the weld joint of 4Cr10Si2Mo/Nimonic 80A formed by inertia friction welding was studied. It is discovered that thewelds formed included three zones: thermo mechanically affected zone (TMAZ); heat-affected zone and the matrix. The TMAZ comprised two regions: a chemical composition mixture zone (CMZ) and a pure shearing zone (PSZ). The austenite grain of the matrix in the CMZ sizing in 3–5_m contains large numbers of carbides with a size smaller than 50 nm. However, the grain size in PSZ is about 8–10_m. The dislocation density in this zone is much lower than that in CMZ. The carbides in PSZ were mainly distributed at grain boundaries or on shear band. In some locations of high dislocation density, clusters of partite of hundreds of nanometres precipitated from the dislocation networks. Grain size in the heat-affected zone is similar to that in the as-received 4Cr10Si2Mo. Three zones exist in the welds formed by the friction welding process: TMAZ; heat-affected zone and the matrix.
H. Behnken and V. Hauk et al has expressed that, the influences of mechanical and thermal treatments on the macro- and micro stresses in two-phase materials. On samples of an austenitic–ferritic duplex steel the alterations of micro-residual stresses caused by different parameters of material treatments, e.g. deformation rate, deformation temperature, tempering, cooling rates were studied. The friction welding procedure is an example of the combination of all these mechanical and thermal parameters. Its effects on macro- and micro stresses were investigated on friction welded joints of quenched and tempered low alloyed steel, of a duplex steel and on joints between both steels. The distributions of macro- and micro-residual stresses were determined versus the distance from the welding zone and from the surface using X-ray and neutron diffraction. Strain measurements on the compact specimens and on thin plates as well as measurements on both phases allow to separate macro- and micro stresses. Both kinds show up with pronounced profiles. The results reveal that micro stresses should not be neglected in the assessments of X-ray.
Tiejun Ma et.al has attempted a project study of; the microstructure of the linear friction welded Ti–6Al–4V titanium alloy joint was investigated by optical microscope, scanning electronic microscope and transmission electron microscope. Results show that the dynamic recovery and recrystallization resulting from the intensive plastic deformation and fast heating and cooling processes during linear friction welding account for the superfine α+β grains in the weld center. Fine α grain distribute in the β matrix or at the boundaries of β grains. A mass of dislocations networks and metastructures present within the α and β grain has been shown that dynamic recovery is the main mechanism in thermal deformation of TC4. Although the dynamic recrystallization could occur, it is feasible due to the short welding time.
T.J. Ma et.al has experimentally stated the microstructure, impact toughness and fracture characteristics of LFW Ti–6Al–4V joint. The results showed that a sound weld was obtained consisting of a superfine a + b microstructure in the weld center (about 70 lm thickness). The weld presents higher impact toughness (61.3 ± 5.8 J/cm2) than the parent Ti–6Al–4V because of the superfine microstructure formed in the weld. The fracture surface exhibits three typical regions: the thin fibrous zone close to the notch, the radiation zone in the middle and the shear lip zone at the other three sides, corresponding to the crack initiation, propagation and shear failure zones, respectively. The crack develops a short distance along the weld center and thermo mechanically affected zone after its initiation, and then extends into the parent metal due to the lowest impact toughness of the parent.
Mumin Sahin H. et.al, expressed that, aluminium alloy as test material 5083 and square cross-sectional equal channel angular pressing die for severe plastic deformation. Firstly 5083 alloys, as purchased, were joined with friction welding method. The optimum parameters for friction time, upset time, friction pressure and upset pressure, which are necessary for welding, were obtained. Afterwards, 5083 aluminium materials as purchased were prepared as square cross-section and then 1-pass severe plastic deformation was applied to specimen by equal channel angular pressing die. The obtained parts as square form were prepared as cylindrical form by machining and then the parts were joined by continuous drive friction welding equipment that was designed and produced in laboratory conditions before. Later, the tensile strengths of the parts, obtained at optimum conditions, were compared with those of the joined parts.
2.2 INFERENCE FROM LITERATURE SURVEY
From the literature survey. It is clearly identified that friction welding is employed in welding of aluminum alloys. It is understood that the spindle rotation speed, friction pressure, forging pressure plays a major role in the friction welding process. Nowadays industries are facing a major problem in the welding of dissimilar metals. Friction welding can be employed in welding of dissimilar metals.
Rotary friction welding is one of the most economical and efficient production meth- ods for joining similar and dissimilar materials. It is widely used with metals and thermo- plastics in a wide variety of aviation, transport, and aerospace industrial component de- signs. Individually, stainless steel to stainless and aluminium alloy to aluminium alloy are normally easy to weld by fusion welding methods, but the joint of AA7075 to SS304L can be extremely difficult due to the differences in the two materials’ melting temperature, density, strength, and thermal conductivity. Thus, these kinds of problems can be eliminated by a solid-state friction welding technique. Hence, the current study attempts to understand the friction welding characteristics of AA7075 and SS304L dissimilar parts. This study looks into the influence of process parameters, which includes friction pressure, upsetting pressure, and upset time on the axial shortening, hardness, microstructure, and tensile properties of the welds. The optimum parameters for upset time, upset pressure, and friction pressure necessary for welding were obtained.
From the literatures it is understood that the hardness at weld interface is increased by deformation. The metallurgy of the interface of friction welded components is essential for understanding the quality of bonding. Therefore in addition to tensile and dynamic properties, hardness variations within the welding zone were obtained.
It is also understood that the tensile strength of joints increases together with the friction pressure, and it raises a maximum, but it decreases for more friction time and friction pressure. However 7075 is a heat treatable alloy, so strength will be reduced in the weld region.
So far friction welding has been done on materials like high carbon steel, low carbon steel, austenitic stainless steel, ferrite steel, copper alloys, magnesium alloys, aluminium alloy etc. Only a very few works have been identified in friction welding of 7075 aluminium alloys with 304L stainless steel . So 7075 alminium alloy and SS 304L are taken in this investigation.her impact toughness (61.3 ± 5.8 J/cm2) than the parent Ti–6Al–4V because of the superfine microstructure formed in the weld. The fracture surface exhibits three typical regions: the thin fibrous zone close to the notch, the radiation zone in the middle and the shear lip zone at the other three sides, corresponding to the crack initiation, propagation and shear failure zones, respectively. The crack develops a short distance along the weld center and thermo mechanically affected zone after its initiation, and then extends into the parent metal due to the lowest impact toughness of the parent.
Mumin Sahin H. et.al, expressed that, aluminium alloy as test material 5083 and square cross-sectional equal channel angular pressing die for severe plastic deformation. Firstly 5083 alloys, as purchased, were joined with friction welding method. The optimum parameters for friction time, upset time, friction pressure and upset pressure, which are necessary for welding, were obtained. Afterwards, 5083 aluminium materials as purchased were prepared as square cross-section and then 1-pass severe plastic deformation was applied to specimen by equal channel angular pressing die. The obtained parts as square form were prepared as cylindrical form by machining and then the parts were joined by continuous drive fri