جستجوی مقالات مرتبط با کلیدواژه « brazing » در نشریات گروه « مواد و متالورژی »

In this research, the effect of temperature and time parameters are investigated on the microstructure and mechanical properties of  dissimilar brazing of 17-4 PH stainless steel and Ti-6Al-4V alloy with BNi-2 filler metal. The microstructure of the joint is evaluated with optical and scanning electron microscopes and the mechanical properties of the joint are also evaluated with tensile-shear and microhardness tests. It can be seen that at a constant temperature of 1050°C, increasing the time from 15 to 30 minutes decreases the shear strength from 34.66 to 29.39 MPa. Formation of brittle intermetallic compounds like NiTi2 and FeTi2 increase strength and promote brittle fracture.At a fixed time of 15 minutes, increasing the temperature from 1050 to 1100 °C causes the strength to increase from 34.66 to 38.46 MPa. Also, the increase in temperature and time increases the ISZ thickness formed in the joints on the side of the filler metal - Ti-6Al-4V from 41.40 to 81.48 microns. The increase in temperature and time also causes more diffusion of boron into the SS-filler joint, which forms various boron compounds and widens this region.

High entropy alloys are especially suitable for use as filler metals in brazing due to their excellent properties. in the present study, three powders with the composition of CoxCrxCuxFexMnxNix (X atomic percentage of the element) were designed using the criteria of these alloys as well as jmatpro software. in the next step, using mechanical alloying, filler nano powder was synthesized and characterized by X-RAY analysis (XRD) test and the effect of filler composition on the thermal behavior of the alloy was studied. then the filler was used in Inconel 600 super alloy brazing, the single-phase solidification behavior and the absence of boron and silicon in the high entropy filler led to the creation of a continuous microstructure without eutectic components or brittle phases in the brazing interface. thus, the shear strength test was performed and 545 MPa  was the highest shear strength obtained among the three filler compounds. in brazing conventional filler metal, incomplete isothermal solidification and subsequent thermal solidification of the residual liquid results in large grains of chromium-rich boride phase distributed throughout the microstructure. not using compounds that lower the melting point in the filler for the purpose of joining the nickel-based superalloy is considered an important step in reducing the subsequent brazing processes.

Brazing of low-carbon austenitic stainless steel sheets is applied to produce plate heat exchangers. In this study, the copper filler was used to join multiple layers of 316L steel plates due to its low cost, low melting temperature and relatively good bonding strength compared to other filler metals. For comparison, 2-layer and 5-layer specimens were brazed with the copper interlayer. fabricated. The sandwich joints have been fabricated under different process conditions of the brazing temperature (1070 and 1120°C) and the brazing time (30, 60, and 90 min). Detailed microstructural studies and hardness were carried out on the brazed joints. The microscopic studies showed that the joint formed at 1070 °C was not uniform compared to 1120 °C and the specimen brazed at 1120°C/90 min presented better properties due to enough time for melting of the interlayer and diffusion of elements. Also, 2-layer specimens with lower average grain size had higher hardness than 5-layer specimens.

In this paper, failure mechanism of a 17th stage blade of an 82.5 MW steam turbine that caused damage to the internal turbine compartment and the adjacent blade equipment has been studied. In order to determine the cause of failure and prevent similar events, various metallurgical and mechanical investigations including chemical composition analysis, metallography and microstructural analysis, fractography using scanning electron microscope and hardness and tensile tests were carried out. The initial results showed that the alloy had a chemical composition, microstructure and mechanical properties in the acceptable range, and the fracture failure was not due to the mechanical and metallurgical degradation during the service. The results of the fractography indicate high cycle fatigue as the main mechanism of the failure and shows that the fatigue crack has initiated from the adjacent hole relative to the vibration damped wire near to the brazing region on the blade, due to inadequate quality and incomplete connection of the brazing and its stress concentration effect the hole, which eventually has propagated and reached a critical level, and a sudden failure of the blade has occurred.

In this study, using Ag-Cu brazing metal alloy, effects of brazing time on microstructure and strength of Al2O3 / Ti6Al4V joints were investigated. Therefore, ceramic/metal couple brazed by electrical furnace. Then, brazed specimens were examined by scanning electron microscope and x-ray diffraction tests. Several phases observed at the interface area and EDS analysis were recognized titanium, copper, silver, aluminum, vanadium and oxygen in this phases. With more study using x-ray diffraction patterns and phases diagrams some intermetallic compounds identified. This compounds were Ti-Cu intermetallices near to Ti6Al4V side and reactive layer of Cu2O ૠ┻ near to Al2O3 ceramic side. Also, microstructural surveys revealed the narrow reaction layer and a little intermetallic compounds in specimen brazed for 10 minutes. With increasing brazing time, reaction layers grossed rapidly. This chemical variation made dimensional changes at metal/ceramic interface. Therefore, some crakes observed in specimen brazed for 25 minutes. Maximum of shear strength equal 295 Mpa measured in specimen brazed for 15 minutes.

Joining of titanium alloys to other materials especially steels has attracted much attention in recent years due to the exceptional properties of titanium such as excellent corrosion resistance and mechanical properties and its increasing application in various industries. According to the Fe-Ti binary phase diagram, these two elements do not have complete solubility. This leads to difficulties during fusion welding of these two alloy. One of the best methods for joining dissimilar alloys is brazing. In this research, the metallurgical and mechanical properties of brazing lap joints of steel to commercially pure titanium using a commercial filler metal (BAg-8) made under different time and temperature conditions were investigated. The study of the microstructure interface shows the formation of a chemical layer close to the titanium side of the joint, while no chemical compounds were created on the steel side. A coarse structure is formed at the interface between the steel and silver solder alloy. The observed coarse grain structure is related to the grain growth along with recrystallization in the steel substrate at high temperatures. Analysis of the joints was carried out by optical microscopy, scanning electron microscopy, X-ray diffraction and hardness measurements. The results show that with increasing temperature, as well as brazing time, the average shear strength decreases due to the increased thickness of the intermediate layer.

Nowadays, cemented carbides-steels joints by brazing method are taken into consideration. One of the problems of these joints is the creation residual stresses that can reduce it with choose correct parameters of brazing. In this study, Silver base alloy filler containing copper, zinc and cadmium have been used in temperature 780°C and the effect of time parameter 5, 10 and 15 minutes on microstructure and mechanical properties were investigated. The results indicated that brazing in 15 minutes causes a columnar growth of solid solution phase of copper from cemented carbide side to steel and provides maximum strength of 94MPa. As well as, by passing of time wetting angle of cemented carbide surface reduces from 40° to about 27°.

In the present study, 5083 aluminium alloy sheets by tungsten inert gas welding­-­brazing were joined to galvanized steel sheets with 4043 and 4047 filler wires. The amount of the weld heat and filler metal type influence the­ mechanical and microstructural properties of the resultant joint. The results obtained from microstructural observation showed that with equal weld heat input the thickness of brittle intermetallic compound layer for the joint produced with 4047 filler metal was approximately half of that for joint produced with 4043 filler metal. Energy­ dispersive x-­ray spectrometry analysis results­ showed that the IMCs layer formed in interface of steel-weld seam consisted of Fe­(Al, Si)3 phase­ in side of steel and Al7.3Fe1.7 Si phase in side of welded seam. ­It was found that the joint produced with 4047­ filler metal exhibit­ed higher mechanical resistance of 170 MPa than that produced with 4043­ of 120 MPa. The results of­ x-ray diffraction analysis conducted on the fracture plane showed the presence of Al0.5Fe3Si0.5 phase. Moreover, for joints produced with 4047 filler metal, the FeSi2 phase­­ created from enriching of Si atoms in IMCs layer was seen.

In this research، Ti-6Al-4V alloy was brazed with 410 stainless steel by three different filler metals as silver-base، nickel-base، and titanium-base alloys. In order to obtain optimum clearance، brazing was done in three different clearances of 0. 02، 0. 04 and 0. 06 mm. Also، the strength and hardness of the brazing zone were investigated. The results of shear strength showed that the brazed samples with titanium-base alloy at the clearance of 0. 02 mm had the maximum strength among the different samples which was 149. 5 MPa.

Microstructural and mechanical properties of dissimilar bonding of INCONEL 625 and 316L austenitic stainless steel using AWS BNi-2 has been evaluated. The bonding process was done at 1020◦C for 30،60 and 120 minutes، respectively with Argon protection followed by homogenization at the temperature of 1080◦C for 4 hour. Chemical analysis from the joint clearance microstructure and mechanical data indicated that the higher the bonding time from 30 to 120 minutes، the lower fraction of precipitates at the joint centerline. Given this، the ultimate shear tensile strength raised from 265 MPa to 360 MPa. Post-bonding homogenization led to more uniform microstructure along with mechanical properties. Moreover، the ultimate shear tensile strength increased to 520 MPa، too.