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Total 22 records
Failure analysis of brazed air passages of an aircraft fuel system
, Article Engineering Failure Analysis ; Volume 17, Issue 6 , 2010 , Pages 1495-1499 ; 13506307 (ISSN) ; Behjati, P ; Madaah Hosseini, H. R ; Kokabi, A. H ; Sharif University of Technology
2010
Effect of joint clearance and post-braze heat treatment on the microstructure of joints with BNi-4 filler metal and 4130 steel
, Article IBSC 2012 - Proceedings of the 5th International Brazing and Soldering Conference ; 2012 , Pages 410-413 ; 9781615039753 (ISBN) ; Kokabi, A. H ; Behjati, P ; Madaah Hosseini, H. R ; Sharif University of Technology
2012
Abstract
In this work, the influence of the clearance and post-braze heat treatment on the microstructure of 4130 steel joint brazed by BNi-4 filler metal was investigated. Samples with different clearances were heated to 1100°C and hold for 9 min. Then, some were reheated to 800°C(2hr) and 800°C(2hr)+1000°C(2hr), cycle 1 and cycle 2, respectively. Microscopy techniques and micro-hardness test were used to evaluate the microstructures. Results suggested that in this case 25μm clearance can be considered as the optimum value. Also, it was found that high temperature post-braze heat treatment can be applied as a useful technique for decreasing the fraction of the brittle phases at the joint main body
Study of the Effect of Molybdenum on Wear Properties and Mechanical Properties of Claded Manganese Steel Created with the Cored Wired Filler Metal
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor) ; Davami, Parviz (Co-Advisor)
Abstract
Hadfield’s manganese steel, nominally Fe–1.2%C–13%Mn, is an alloy with inherent toughness, work-hardening characteristics and excellent resistance to some types of adhesive and abrasive wear. However, due to its low yield strength, it may be deformed markedly before its work-hardening become effective. There have been many studies on increasing strenght by alloying manganese steel, but the effects some other alloying additions such as 1 to 2 percent Al, Cr, W, V despite increase strenght and wear resistance at the low stress abrasive condition, decrease work-hardening characteristics and wear resistance at the high stress abrasive condition. The aim of present work, is to modify...
Microstructural Evaluation during dissimilar transient liquid phase bonding of TiAl/Ni-based superalloy
, Article Journal of Alloys and Compounds ; Volume 825 , June , 2020 ; Kaflou, A ; Gholamipour, R ; Pouranvari, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The paper aims at understanding solidification phenomena and solid state precipitations during dissimilar transient liquid phase bonding of γ-TiAl intermetallic compound to IN718 Ni-based superalloy using a quinary Ni–7Cr–3Fe–4.5Si–3.2B (wt%) filler metal. The mechanisms of intermetallic formation via solidification and solid state reactions are discussed. The joint is featured by the formation of Ni-rich solid solution in an isothermal solidification zone near to IN718, Ni-rich solid solution and isostructural binary phases solid solution designated as Al1-xNi3Six in an isothermal solidification zone near to TiAl, boride/silicide and boro-silicide formation during binary and ternary...
Ring-like laser spot welding of Ti grade2 to AAl3105-O using AlSiMg filler metal
, Article Optik ; Volume 206 , 2020 ; Sadrnezhaad, S. K ; Torkamany, M. J ; Fakouri Hasanabadi, M ; Alali, M ; Mahmoud, A. K ; Abass, M. H ; Kokabi, A. H ; Sharif University of Technology
Elsevier GmbH
2020
Abstract
A pulsed Nd:YAG laser welding of 1 mm thick Ti (grade 2) to 0.5 mm thick AA3105-O was performed by a ring-like spot joining. A 0.15 mm thick Al-12Si-2.5 Mg alloy was used as a filler metal. Intermetallic compounds of Ti3Al, Ti2Al, TiAl, Ti(Al,Si)3 and Mg2Si were observed respectively from Ti towards Al sides at the fusion zone. Si and Mg increased the strength of the Al re-solidified zone near the Ti-Al interface because of their easy dissolution in the Al. Exothermic effect of the Mg addition resulted in porosity in the welding zone. Joint strength of up to 98% of the Al base metal was obtained, which was much 14% higher than that achieved by autogenous welding. © 2019 Elsevier GmbH
Microstructure and Wear Properties of WC/CuZnNi Compsite Surface Coating
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor) ; Aashuri, Hossin (Supervisor)
Abstract
The microstructure and wear performance of WC/Cu-Zn-Ni composite surface coating has been investigated using a combination of microscopy, hardness, and wear testing. The oxidation behavior of tungsten carbide hard metal in the temperature range between 600 and 900 ◦C was also researched. The oxidation mass gain of WC correlated almost directly with temperature as well as time. The particle of hard metal is surrounded by the α Cu+β Zn phase in the surface coating. The size of hard metal is almost unchanged from its original one. There exists an inter-diffusion zone at the interface of the hard metals and Cu-based matrix. The wear volume of the WC/Cu-Zn-Ni composite surface coatings increased...
On the formation of intermetallics during the furnace brazing of pure titanium to 304 stainless steel using Ag (30-50%)-Cu filler metals
, Article Materials and Manufacturing Processes ; Volume 25, Issue 11 , 2010 , Pages 1333-1340 ; 10426914 (ISSN) ; Abachi, P ; Dehghani, K ; Pourazarang, K ; Sharif University of Technology
2010
Abstract
In the present work, the effect of brazing pa rameters on the properties of the brazed joint of pure titanium and 304 stainless steel (304SS) was investigated. Three different Ag-Cu filler metals were used, while the temperature and time of brazing were in the range of 800-950°C and 5-45 minutes, respectively. The microstructural observations show that, depending on the brazing conditions, different intermetallic phases such as CuTi2, CuTi, Cu3Ti4, and FeTi were formed at the phases interface. Based on the microstructural observations, a model was developed to characterize the formation of phases at the interfaces and brazed joint. The results show that, while some phases may form during the...
Microstructural evolution mechanism during brazing of Hastelloy X superalloy using Ni–Si–B filler metal
, Article Science and Technology of Welding and Joining ; 2017 , Pages 1-7 ; 13621718 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Abstract
The paper aims at understanding solidification phenomena and solid state precipitations during diffusion brazing of Hastelloy X nickel base superalloy using a ternary Ni–4.5Si–3.2 B (in wt-%) filler metal. The joint is featured by the formation of Ni-rich solid solution in an isothermal solidification zone, borides/silicide formation during eutectic-type solidification in an athermal solidification zone, on-cooling precipitation of fine nickel silicides in the joint centerline, in situ precipitation of Mo–Cr-rich borides in the diffusion affected zone and grain growth in the heat affected zone. The implication of the phase transformations on the joint properties is discussed. It is shown...
Fast isothermal solidification during transient liquid phase bonding of a nickel alloy using pure copper filler metal: solubility vs diffusivity
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 50, Issue 5 , 2019 , Pages 2235-2245 ; 10735623 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Springer Boston
2019
Abstract
This investigation aims at understanding the underlying fundamentals of the isothermal solidification phenomenon during the transient liquid phase (TLP) bonding process. The isothermal solidification is governed by solid-state diffusion of the melting point depressant (MPD) into the base material, which, in turn, is controlled by both kinetic and thermodynamic parameters; however, the latter factor is generally ignored. In this work, the competition between kinetics and thermodynamics of diffusion were considered in TLP bonding of a nickel alloy, Monel 400, using two distinct filler metals including pure copper (Cu) and Ni-Si-B filler metal. The joint generated by Ni-Si-B filler metal...
Conventional vs. temperature-gradient transient liquid phase bonding of stainless steel 304 using a multi-component (Fe–Ni–Mo–B) filler metal
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 53, Issue 11 , 2022 , Pages 4081-4100 ; 10735623 (ISSN) ; Ekrami, A ; Sharif University of Technology
Springer
2022
Abstract
The application of the multi-component Fe-based filler metals (FMs) for transient liquid phase (TLP) bonding of AISI 304 austenitic stainless steel has been overshadowed by dissimilar interlayers merely due to their shorter isothermal solidification time. However, the latter usually suffers from low efficiency in terms of mechanical properties even after homogenization of heat treatment. This study shows that by imposing a temperature gradient across the bond line during the TLP bonding process (TG-TLP), it is possible to reduce the isothermal solidification time significantly. This renews the interest in utilizing multi-component Fe-based FMs. In this regard, the TG-TLP bonding process was...
Factors affecting strength of dissimilar TiAl/Ni–Si–B/Ni-based superalloy brazed joint
, Article Journal of Materials Science ; Volume 57, Issue 8 , 2022 , Pages 5275-5287 ; 00222461 (ISSN) ; Kaflou, A ; Gholamipour, R ; Pouranvari, M ; Sharif University of Technology
Springer
2022
Abstract
This paper addresses the process-microstructure-strength correlation during dissimilar brazing of TiAl alloy to IN738 Ni-based superalloy using Ni–4Si–3.2B filler metal. The solid/liquid reactions, solidification phenomena, and solid-state phenomena are analyzed. The thickness of the athermal solidification zone and reaction layer at different bonding conditions (holding times and temperatures) determined and analyzed using a Larson–Miller parameter (LMP). It was resulted that the shear strength of the joint can be formulated regarding bonding temperature and holding time through using LMP. It was found that the sizes of athermally solidified zone and reaction layer are two key factors...
Microstructure, fractography, and mechanical properties of hardox 500 steel tig-welded joints by using different filler weld wires
, Article Materials ; Volume 15, Issue 22 , 2022 ; 19961944 (ISSN) ; Haowei, M ; Yarigarravesh, M ; Assari, A. H ; Tayyebi, M ; Tayebi, M ; Hamawandi, B ; Sharif University of Technology
MDPI
2022
Abstract
This paper deals with the effects of three low-carbon steel filler metals consisting of ferritic and austenitic phases on the weld joints of the tungsten inert gas (TIG) welding of Hardox 500 steel. The correlation between the microstructure and mechanical properties of the weld joints was investigated. For this purpose, macro and microstructure were examined, and then microhardness, tensile, impact, and fracture toughness tests were carried out to analyze the mechanical properties of joints. The results of optical microscopy (OM) images showed that the weld zones (WZ) of all three welds were composed of different ferritic morphologies, including allotriomorphic ferrite, Widmanstätten...
Study on microstructure and mechanical characteristics of low-carbon steel and ferritic stainless steel joints
, Article Materials Science and Engineering A ; Vol. 608, issue , 2014 , pp. 35-45 ; ISSN: 09215093 ; Mostafaei, M. A ; Pouraliakbar, H ; Kokabi, A. H ; Sharif University of Technology
Abstract
In this work, examinations on the microstructure and mechanical properties of plain carbon steel and AISI 430 ferritic stainless steel dissimilar welds are carried out. Welding is conducted in both autogenous and using ER309L austenitic filler rod conditions through gas tungsten arc welding process. The results indicate that fully-ferritic and duplex ferritic-martensitic microstructures are formed for autogenous and filler-added welds, respectively. Carbide precipitation and formation of martensite at ferrite grain boundaries (intergranular martensite) as well as grain growth occur in the heat affected zone (HAZ) of AISI 430 steel. It is found that weld heat input can strongly affect grain...
The effects of functionally graded material structure on wear resistance and toughness of repaired weldments
, Article Materials and Design ; Volume 32, Issue 2 , February , 2011 , Pages 892-899 ; 02641275 (ISSN) ; Barzegari, M ; Kokabi, A. H ; Mirazizi, M ; Sharif University of Technology
2011
Abstract
To perform a long lasting, crack-free repair welding on ultrahigh strength steels, the filler metal must be chosen and applied properly. Avoiding several short-term repairs or replacements, the repaired weldment should reveal comparative characteristics such as wear resistance, toughness and hardness to base metal. In the present study, a novel functionally graded material have been introduced to obtain enhanced wear resistance and hardness at surface as well as improved fracture toughness at fusion line of repaired weldments. A comparative study of wear resistance of repaired weld metals has been carried out by pin-on-disk apparatus at 5N normal load and 0.14ms-1 sliding speed. Fracture...
Novel manufacturing process of nanoparticle/Al composite filler metals of tungsten inert gas welding by accumulative roll bonding
, Article Materials Science and Engineering A ; Volume 648 , 2015 , Pages 47-50 ; 09215093 (ISSN) ; Noei Aghaei, V ; Dabiri, A. R ; Amirkhanlou, S ; Akhavan, S ; Fattahi, Y ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
In the present work, accumulative roll bonding (ARB) was used as an effective method for manufacturing nanoparticle/Al composite filler metals of tungsten inert gas (TIG) welding. After welding, the distribution of ceramic nanoparticles and mechanical properties of welds were investigated. By applying ARB, ceramic nanoparticles were uniformly dispersed in the composite filler metals. Consequently, the welds produced by these filler metals had a uniform dispersion of ceramic nanoparticles in their compositions. The test results showed that the yield strength of welds was greatly increased when using the nanoparticle/Al composite filler metals. The improvement in the yield strength was...
An investigation into welding of 304 stainless steel to a medium carbon steel
, Article Welding in the World ; Volume 53, Issue SPECIAL ISSUE , 2009 , Pages 575-580 ; 00432288 (ISSN) ; Nasiri, A. M ; Kokabi, A. H ; Serajzadeh, S ; Sharif University of Technology
Abstract
In this work, fusion welding of CK45 carbon steel and 304 stainless steel was performed using GTAW technique. Both ER308-L and ERNi-1 filler metals with and without buttering conditions were employed. Then, the welded samples were studied utilizing optical metallography, scanning electron microscopy, microhardness, polarization and impact tests. It is observed that in the buttered specimens with nickel wire, the structure of weld metal was completely austenitic while the microstructure of unbuttered one was austenitic-ferritic and also, a carburized region in the weld metal next to the fusion line were observed. Microstructures and microhardness variation in the weld metal after socking at...
Microstructure evolution mechanism during post-bond heat treatment of transient liquid phase bonded wrought IN718 superalloy: An approach to fabricate boride-free joints
, Article Journal of Alloys and Compounds ; Volume 723 , 2017 , Pages 84-91 ; 09258388 (ISSN) ; Ekrami, A ; Kokabi, A. H ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
The microstructure of a transient liquid phase (TLP) bonded nickel base superalloy using B-containing filler metal after completion of isothermal solidification can usually be described by a eutectic-free joint centerline with extensive in-situ boride precipitation in the diffusion affected zone which in turn can affect the joint properties. Therefore, designing a proper post-bond heat treatment is needed to produce a robust joint. This paper addresses the microstructure evolution mechanism during post-bond heat treatment (PBHT) of TLP bonded wrought IN718 nickel base superalloy. PBHT at 1150 °C, which is lower than the solvus temperature of the borides, for 12 h resulted in boride-free...
Microstructural evolution mechanism during brazing of Hastelloy X superalloy using Ni–Si–B filler metal
, Article Science and Technology of Welding and Joining ; Volume 23, Issue 5 , 2018 , Pages 441-448 ; 13621718 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
The paper aims at understanding solidification phenomena and solid state precipitations during diffusion brazing of Hastelloy X nickel base superalloy using a ternary Ni–4.5Si–3.2 B (in wt-%) filler metal. The joint is featured by the formation of Ni-rich solid solution in an isothermal solidification zone, borides/silicide formation during eutectic-type solidification in an athermal solidification zone, on-cooling precipitation of fine nickel silicides in the joint centerline, in situ precipitation of Mo–Cr-rich borides in the diffusion affected zone and grain growth in the heat affected zone. The implication of the phase transformations on the joint properties is discussed. It is shown...
High content of boride-forming elements in in617 nickel-based superalloy enables short isothermal solidification time during transient liquid phase bonding
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 51, Issue 11 , 2020 , Pages 5715-5724 ; Ghasemi, A ; Pouranvari, M ; Sharif University of Technology
Springer
2020
Abstract
Isothermal solidification stage during transient liquid phase bonding is the key to preclude intermetallic phase formation during solidification of the liquid phase. The rate of isothermal solidification is controlled by solid-state diffusion. Therefore, the bonding time required to complete isothermal solidification is generally long. This paper reports a very short isothermal solidification time for transient liquid phase bonding of IN617 solid solution nickel-based superalloy using a boron-containing filler metal. A eutectic-free bond with limited grain growth in the base material with high shear strength is achievable by utilizing a short (i.e., 5 minutes) thermal bonding strategy. The...
Laser welding of titanium grade 2 and aluminium AA 3105-O using a new AlScZr filler metal
, Article Lasers in Manufacturing and Materials Processing ; Volume 9, Issue 1 , 2022 , Pages 37-55 ; 21967229 (ISSN) ; Sadrnezhaad, S. K ; Alali, M ; Fakouri Hasanabadi, M ; Torkamany, M. J ; Abass, M. H ; Mahmoud, A. K ; Kokabi, A. H ; Sharif University of Technology
Springer
2022
Abstract
In this study, a pulsed Nd:YAG laser welding method is implemented to join Ti-G2 (1 mm thick) to AA3105-O (0.5 mm thick) via a ring of spots filled with AlScZr alloy (0.15 mm thick). The filler material improved the weld’s microstructure and mechanical properties by reducing the undesirable intermetallic compounds (IMCs) such as TiAl2 and TiAl3 in the aluminium re-solidified zone near the titanium/aluminium interface. The joints having AlScZr filler were mostly failed at Al heat affected zone (HAZ) during the tensile shear test. The addition of zirconium to binary Al–Sc system formed a substitutional solid-solution in which 50 wt% Zr+10 wt% Ti replaced Al3(Sc,Zr,Ti). Scandium had a...