Showing 7 results for Superalloy
S. Sakiyan, H. Sabet, M. Abbasi ,
Volume 2, Issue 1 (8-2016)
Abstract
This Paper presents the welding parameter's effect (forging pressure, welding time) on macrostructure and mechanical properties of friction welding valve steel HNV3 to Nimonic 80A super alloy. For this purpose, two rods with 20 mm diameters are prepared and with using different parameters (Increase forging pressure and welding time) by friction welding method are welded together. Tensile Test carried out on samples for investigating the effect of a parameter. It was discovered that when the welding parameters used in connecting HNV3 and Nimonic 80A Superalloy couple through friction welding were selected correctly; strength of the connection would increase compared to the main material.
Dr Seyed Rahim Kiahosseini, Mr Mostafa Teymoori,
Volume 3, Issue 2 (1-2018)
Abstract
Friction stir welding (FSW) is a new method that the joining is carried out by friction between two metals and heat creation. The stress concentration phenomena in welded joint cause the stress increasing in welded zone. In this research, modeling and analysis of similar junction of IN718 and Mar-M247 and non-similar junction of IN718-Mar-M247 superalloys were performed by ANSYS Software and finally the stress concentration factors of welded samples were calculated. The stress concentration factor of similar and non-similar of junctions was assessed and compared with reported experimental data in the literatures. The results showed that, the mean stress concentration factor for similar junction of Mar-M247 and IN718 superalloys are 1.566 and 1.63 respectively and for non-similar junction is equal to 1.52.
I. Saydi, R. Dehmolaei, Kh. Ranjbar,
Volume 8, Issue 1 (8-2022)
Abstract
In this research, the diffusion bonding of the stabilized zirconia ceramic and Nimonic 105 superalloy using Ti/Nb/Ni multi-interlayer was carried out. Joint was performed using the plasma spark technique in a vacuum atmosphere and at different temperatures and times. The microstructure of the different joint zones was studied using optical and FESEM microscopes equipped with an EDS analyzer. The results showed that the critical region is Ti/3YSZ interface and in all conditions diffusion bonding in Ti/Nb, Nb/Ni, and Ni/NI 105 interfaces were done. Microstructural observations showed that in the Ti/3YSZ interface at all temperature and time conditions, the connection of two separate regions including Ti3O and (Zr, Ti)2O was formed due to the difference in the diffusion depth of Ti, Zr, and O elements and with increasing temperature and time, the thickness of these regions increased. Microstructural studies showed that the bond at 900 ℃ and 30 minutes did not have any cracks and discontinuities and due to the better diffusion of atoms, a suitable reaction layer was formed. Microhardness observations and EDS analyses confirmed that the Ti3O reaction layer is the weakest zine.
R. Mahdizade, S. A.asghar Akbari Mousavi, S. Mehdipour,
Volume 9, Issue 2 (1-2024)
Abstract
In this study, non-homogenous welding of nimonic 75 superalloy to Monel 400 with 1 mm thickness was investigated with pulsed Nd:YAG laser welding. The mechanical properties of the joint were analyzed with optical and scanning electron microscope, X-ray diffraction, micro-hardness test and tensile test. In the case of non-homogeneous welding of Nimoinc 75 superalloy to Monel 400, defects such as liquation cracks and porosity in the welded samples were observed. these defects were removed with increasing the preheating temperature and decreasing the heat input. The results showed the voltage, pulse width, pulse frequency and welding speed should be selected as 500 volts, 9 milliseconds, 3 Hz and 0.9 mm/s respectively to reach the proper penetration depth. Also, the investigations show that the welding structure is composed of austenitic matrix containing columnar dendrites and some cellular areas. The mechanical properties of the weld metal were reduced after joining and segregation causes a change in the amount of elements and the appearance of intermetallic compounds in the spaces between dendrites and cells. All non-homogeneous samples broke during the tensile test from the weld metal area.
Ali Adelian, Khalil Ranjbar, Mohsen Reihanian, Dehmolaei Reza,
Volume 9, Issue 2 (8-2025)
Abstract
This study investigated the effects of pulsed current and constant current on the microstructure and mechanical properties of Hastelloy X superalloy welds produced by Gas Tungsten Arc Welding (GTAW), using ERNiCrMo-2 filler metal. Key microstructural parameters, such as elemental segregation, dendrite refinement, and weld metal uniformity, along with changes in weld strength and hardness, were examined and compared between the two welding modes. Microstructural evaluations were conducted using optical microscopy, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), and X-ray Diffraction (XRD) for phase identification. Pulsed current welding resulted in a finer microstructure with more equiaxed dendrites, reduced elemental segregation, and a more uniform distribution of M₆C carbides. Furthermore, this process led to significant improvements in hardness, impact toughness, and tensile strength of the weld metal compared to constant current welding. Fracture analysis confirmed ductile fracture behavior in all specimens, consistent with the microstructural and mechanical findings. The results of this research highlight the importance of using pulsed current in GTAW as an effective method for controlling the microstructure and enhancing the mechanical properties of Hastelloy X alloy joints.
Reza Sahihi, , ,
Volume 9, Issue 2 (8-2025)
Abstract
In this study, the effect of gas tungsten arc welding (GTAW) in both constant and pulsed current modes with frequencies of 5 and 20 Hz was investigated on the weldability, microstructure, and mechanical properties of Inconel 738LC superalloy. The main objective was to evaluate the susceptibility to liquation cracking in the heat-affected zone (HAZ) and to identify the mechanisms responsible for improving weldability. The results revealed that applying pulsed current, particularly at a higher frequency of 20 Hz, significantly reduced the extent of liquation cracking and improved the overall joint quality. The average crack length decreased by more than 50% compared to the constant current condition. Increasing the pulse frequency transformed the solidification morphology from columnar dendritic to equiaxed, reduced interdendritic segregation, and led to a more uniform and finer distribution of MC carbides. The ultimate tensile strength increased from 751 MPa (constant current) to 802 MPa (20 Hz pulsed current), representing an improvement of approximately 6.7%, while the total elongation improved from 7.96% to 9.83% (about 23% increase). The weld metal hardness also increased from 446 to 468 HV. Overall, pulsed GTAW at a moderate frequency (20 Hz) effectively reduced solidification stresses and thermal gradients, providing an efficient approach to mitigate liquation cracking and enhance the mechanical performance of Inconel 738LC welds.
E. Ranjbarnodeh, P. Raissi , A. Kolagar , M. Cheraghzadeh,
Volume 10, Issue 2 (12-2024)
Abstract
Nickel base superalloy IN738LC is widely used in power plant industry and gas turbine blade manufacturing. The main strengthening mechanism of this alloy is the precipitation hardness caused by γ′ precipitates. These precipitates play an important role in determining the mechanical properties of this alloy and their amount and morphology changes under heat treatment. In this research, in order to investigate the evolution of γ' precipitates during heat treatment, a number of solution annealed samples were subjected to arc heat treatment. In this heat treatment, by applying heat caused by a static arc, a temperature ranges from the ambient temperature to above the melting point is created in the sample. Using this process, samples with 100 amp currents were heat treated for 1, 2 and 15 minutes. Electron microscope, image processing and transient heat transfer model with axial symmetry were used for experimental and mathematical investigations. In the following, using the experimental and numerical results simultaneously, a mathematical model for the dissolution kinetics of γ' precipitates in the heat-affected zone of these welds was presented. The results of electron microscopy showed that the dissolution rate and shape of γ′ precipitates are strongly influenced by the distance from the heat source. The activation energy of dissolution of γ′ precipitates increased with increasing time and its value was between 40 and
80 kJ/mol.
