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The Evaluation of Microstructure and Mechanical Properties of a HSHR Stainless Steel Strengthen by Nano-Precipitates
, Ph.D. Dissertation Sharif University of Technology ; Karimi Taheri, Ali (Supervisor) ; Davami, Parviz (Co-Advisor)
Abstract
In this research, a computational method based on thermodynamic and physical metallurgy coupled by the d-electron approach was used to design the composition of a high strength and heat resistant (HSHR) stainless steel. Then, three series of the heat resistant 25Cr-35Ni-Nb (HP-Nb) stainless steels with tungsten, nitrogen, and micro alloying elements additions were cast. In these alloys a Nb/(C+ 6/7 N) ratio of ≈ 2.4 to 3.7 was chosen and they were directionally solidified under two cooling rates of 23 Ks-1 and 6 Ks-1. The effects of the alloy chemical composition and solidification cooling rate on the macrostructure, microstructure, microsegregation, and inclusions in the alloys were...
Microstructural and Mechanical Properties of TLP Bonded SS 304 with Fe-base Interlayer
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor)
Abstract
Cooling sandwich panels are one of the components of the heat exchangers used to cool the components of the sandwich panels . One of the applications of TLP Bonding for steel can be called cooling sandwich panels. In this research , TLP of 304 Stainless Steel , using Fe-base interlayer at 1200 C has been investigated . Cross section of bonded samples were examined by optical and scanning electron microscopes. Microscopy results revealed that 2h is sufficient for completion of isothermal solidification and there is no eutectic compound at bonding zone . Bonding in this condition resulted in the free precipitates in the diffusion affected area. By analyzing eutectic phase in bonding areas at...
Effect of Laser Shock Peening on Fretting Fatigue Behaviour of 316L Stainless Steel
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor)
Abstract
Fretting fatigue occurs at the point of contact of two parts that are under dynamic loading. During this phenomenon, due to the force applied at the contact point, deformation occurs and causes slip-stick zones, which intensifies the effect of surface degradation and crack nucleation happens earlier. In this research, the improvement of fretting fatigue life under combined loading by induction of compressive residual stresses by laser pinning process in the sample has been investigated. The laser shock peening process is a method by which residual stress is created in the sample and can improve fatigue life. The material used is 316L stainless steel, which has many industrial applications....
Combined Fretting Fatigue Life Estimation Based on the Theory of Critical Distances
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor)
Abstract
Theory of Critical Distances (TCD) is one of the methods that has attracted the scientists in life estimation of fretting fatigue problems in recent years. Less difficulty and less time consuming features of this method in comparison with other methods like fracture mechanics are the attracting aspects of this theory. In this research, the capability of the Theory of Critical Distances in life estimation of combined bending and tensile loading modes in fretting fatigue for the pads with sharp edges has been evaluated. This included the evaluation of this method in lifetime estimation of 316L stainless steel for fretting fatigue in two different types of heat treatments and the evaluation of...
Effect of Cryogenic Treatment on Distribution of Residual Stress and Wear Resistance of AISI 316 and AISI 304 Stainless Steel
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor)
Abstract
Various methods are used to improve the behavior of steel parts. Cryogenic treatment is one of the prevalent methods used for this purpose. It is not a substitute process but rather a supplement to conventional heat treatment process. In this Study the effect of the minimum temperature and the time of cryogenic treatment on wear resistance and residual stress of stainless steel AISI 316 and AISI 304 were studied. For this purpose conventional heat treatment, deep cryogenic treatment (24, 48 and 72 hours) and shallow cryogenic treatment (5, 10 and 15 hours) were performed on the samples. The wear resistance were measured by Pin-on-disk test according to the standard G99-95 (under the load of...
Production of 316 L Steel Alloy Powder by Thermal Spraying Method for Selective Laser Melting Additive Manufacturing Process
, M.Sc. Thesis Sharif University of Technology ; Sadrnejad, Khatib al-Islam (Supervisor)
Abstract
Powder production for additive manufacturing processes is one of the daily challenges of researchers. The aim of this research is to produce 316 L stainless steel powder using a new flame spraying method. Flame spraying is the oldest thermal spraying process, which has always been of interest due to its high efficiency and relatively low side costs. 316 L stainless steel wire with a diameter of 3 mm was used to produce the powder; The input material was entered at a temperature of 01°C and was melted with the help of acetylene and oxygen flame and sprayed as a powder, the powder production rate was kg/h0. To collect the produced powder, a cylindrical tank with a diameter of 01 cm and a...
Effect of Process Parameters on Microstructure and Mechanical Properties of Duplex Stainless Steel Produced by Wire-Arc Additive Manufacturing
, M.Sc. Thesis Sharif University of Technology ; Ashouri, Hossein (Supervisor) ; Movahedi, Mojtaba (Supervisor)
Abstract
Wire-arc additive manufacturing is one of the types of additive manufacturing methods that creates the desired part through layer-by-layer deposition. Heat input and interlayer temperature have an important role in this process. Duplex stainless steels have a wide range of applications due to their high corrosion resistance in chloride environments and higher strength than austenitic stainless steels. In this study, the effect of heat input (0.3 kJ/mm and 0.8 kJ/mm) and interlayer temperature (250 ºC and 40 ºC) was investigated on the macrostructure, microstructure and mechanical properties of 2209 duplex stainless steel walls that produced by gas metal arc welding based wire-arc additive...
Investigating The Transformation Of Strain-Induced Martensite During Deformation and its Effect on the Wear Behavior of Austenitic Stainless Steel
,
M.Sc. Thesis
Sharif University of Technology
;
Serajzadeh, Siamak
(Supervisor)
Abstract
In austenitic stainless steel types 304 and 316, due to the instability of the austenite phase, the martensite phase is formed by plastic deformation below the Md temperature. In this research, the cold rolling of 304L austenitic stainless steel and the transformation of austenite to strain-induced martensite and its effect on mechanical properties, especially wear, were studied. In this way, the samples were rolled in two modes and four passes in each mode. In the first case, the samples were cooled between each pass in water as a cooling liquid, and in the second case, the samples were cooled in each pass without using water and by air. Next, tests such as hardness measurement, uniaxial...
Preparation of HA/Al2O3/MgO Biocompatible Nanocomposite Coating by Electrophoretic Method on 316 Stainless Steel
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah (Supervisor)
Abstract
In this research, it has been tried to use alumina and magnesia nanoparticles to hydroxyapatite nano powder, a three-component coating, with corrosion resistance, adhesion and desirable biocompatibility on the 316 stainless steel substrate, by electrophoretic method. It should be applied at 3 voltages of 10, 30 and 50 volts and for 3 minutes. TEA was used as a dispersing agent and ethanol as a solvent to prepare the suspension. Alumina nano powder was added to nanohydroxyapat in two amounts of 10 and 20% by weight and 20% was optimized as the amount, and magnesia nano powder was added to the composition in three amounts of 1, 3 and 5% by weight, which was 3% by weight of the results Was...
Produce of Antibacterial Composite Coating of PTFE+Ag+TiO2 On 316SS and Study Its Properties
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah (Supervisor)
Abstract
This research investigated the corrosion and antibacterial properties of PTFE+TiO2/Ag coating and its adhesion to 316L stainless steel. To increase adhesion, polydopamine coating was created as an intermediate layer by chemical deposition method on stainless steel, then PTFE + TiO2 coating was created on the sample by immersion method, and then silver nanoparticles were applied as the third layer by chemical deposition method. According to the polarization curves, the most corrosion-resistant coatings with corrosion current density of 3.34×10-5 and 3.25×10-4 μA are coatings PTFE+TiO2 and PTFE/PTFE+TiO2/Ag respectively. In terms of antibacterial activity, according to the non-growth halo...
Characterization of Ss316l Powder Produced by Flame Spraying Method for Additive Manufacturing by Selective Laser Melting by Changing Machine Parameters
, M.Sc. Thesis Sharif University of Technology ; Sadrnezhaad, Khatiboleslam (Supervisor)
Abstract
Selective Laser Melting (SLM) process is a powder-based metal Additive Manufacturing (AM) technique. This developing industry has many advantages like generation of geometrically complex shapes with high density. High Cost, production and characterization of powders, limited material choices and process parameters optimization are some of the challenges associated with SLM. Stainless steel 316L due to its unique properties, like corrosion resistance, high strength, biocompatibility, availability and cost is indeed a commonly used material in SLM. In this research, the characterization of the powder produced by the flame spraying device, which is a new method, was discussed. Wire with 3mm...
Produce of Nano composite Antibacterial Coating of PDMS+TiO2+ Ag3PO4 on 316SS Using Sol-Gel Methods and its Properties
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdullah (Supervisor)
Abstract
The aim of this research is to create coatings with antibacterial and superhydrophobic properties. To evaluate this, the sourness angle test, bacterial culture and halo diameter test have been used. The results show that 316L stainless steel containing PDMS+TiO2+7%Ag3PO4 coating, which is applied by immersion method on the substrate, has a water contact angle of 152 degrees, the number of bacteria cfu.cm2 is 44000 and the halo diameter is 24 mm. which has the best performance among other examples. In order to increase the adhesion of coatings on 316L stainless steel, first heat treatment was performed and then the samples were placed in H2SO4:H2O2 solution for 1 hour to form its OH- groups...
Study of The Effect of Strain Rate on Cold Deformation Behavior and Mechanical Properties of 304L Austenitic Stainless Steel
, M.Sc. Thesis Sharif University of Technology ; Serajzadeh, Siamak (Supervisor) ; Karimi Taheri, Ali (Supervisor)
Abstract
The stiffness rate of the 300 series austenitic stainless steel has long been known to depend on the stability of the austenite and its susceptibility to martensite formation. In this project, the cold deformation of austenitic stainless steel (304L) and the occurrence of martensite deformation during it are studied. Experimental cold rolling experiments under different strain velocities and initial temperatures in the range of -10° C to 25° C; Performed and microstructure, mechanical properties and percentage of martensite generated in rolled steel are determined and evaluated employing different testing techniques. mathematical modeling of cold rolling operation is also performed using...
Corrosion Behavior of TLP Bonded 304 Stainless Steel Using Cobalt Base Interlayer
, M.Sc. Thesis Sharif University of Technology ; Ekrami, Ali Akbar (Supervisor) ; Tavakoli, Rouhollah (Supervisor)
Abstract
The transient liquid phase bonding is a combination of penetration bonding and hard soldering processes. This method is based on the diffusion in the solid state of the melting point reducing elements from the joint zone into the base metal and isothermal solidification that the kinetics of this reaction are controlled by diffusion in the solid state. In this study, we investigate the bonding of 304 stainless steel with cobalt base interlayer by transient liquid phase method and studies of microstructural and corrosion resistance of the joint. Three different temperatures are considered for the bonding and after each bonding, the microstructure is examined with a optical and scanning...
Modification of Additively Manufactured Stainless Steel 316L Electrodes by Fe-Co-Ni Metal-Organic Framework and Gold Nanoparticle for Electrochemical Water Splitting and CO2 Reduction
, M.Sc. Thesis Sharif University of Technology ; Simchi, Abdolreza (Supervisor)
Abstract
The processes of electrochemical water splitting and carbon dioxide reduction are among novel technologies that have gained attention for tackling climate change and global warming. Though, catalysts with fininancial justification for industrial utilization of these processes is still not available. In this study, a 3D-structured electrode of low-carbon 316 stainless steel, made by additive manufacturing, is modified with a trilayered metal-organic framework (MOF), with Iron, Cobalt, and Nickel metallic nodes and BDC-NH2 as the organic ligand, for water splitting. Also, the same steel electrode is modified with a single layered MOF, with Iron node and BDC-NH2 ligand, along with nanoparticles...
An Investigation on Multistage Strain Aging Using Rolling Process on Mechanical and Formability of Stainless Steel 304L
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor) ; Akbarzadeh Changiz, Abbas (Supervisor)
Abstract
Austenitic stainless steels have extensive and special mechanical properties because of austenite to α΄-martensite transformation due to plastic work. Obtaining a process path that provides maximum strength and flexibility and minimum α΄-martensite content (α΄-martensite increases corrosion current) in these steels is important in the industry. Applying the aging process after applying plastic strain (single-stage aging) results in an increase in strength of up to 200 MPa and an increase in hardness of up to 60 Vickers. However, single-stage aging does not cause significant changes in the amount of α΄-martensite in steel and in the temperature range of 400 to 500 ° C, it causes a slight...
Upset Resistance Welding of Aluminium to Steel
, M.Sc. Thesis Sharif University of Technology ; Kookabi, Amir Hossein (Supervisor) ; Movahedi, Mojtaba (Supervisor)
Abstract
Aluminum and steel are the most utilized metals in industry and joining of them has many applications including heat exchangers and parts in aluminum extraction process. In this research, Upset Resistance Welding of aluminum to stainless steel was studied. In this regard, the effect of current intensity, time of welding, in-situ post-heating operation and post-heating operation in the furnace were investigated on the microstructure, mechanical properties and electrical resistance of welds. The currents of 2.25, 2.30 and 2.35 kA and times of 55, 60 and 65 cycles were applied for welding. Then in-situ post-heating conducted under currents of 1.75, 2.25 and 2.75 kA and 10 cycles on the sample...
Effects of Rolling Process on Mechanical Properties and Formability of Reinforced Polymeric Matrix with Stainless Steel Mesh as Cladding Composite Sheet
, M.Sc. Thesis Sharif University of Technology ; Akbarzadeh, Abbas (Supervisor)
Abstract
In this study, the mechanical properties of composite sheet polymer matrix reinforced with steel mesh were investigated. This bonding was carried out by rolling of a three layers of steel mesh in between two composite polymer sheets. Then, the effective parameters of process; Sample maintenance temperature inside the furnace, reduction during rolling, rolling speed, rolling direction and Number of rolling passes were investigated to determine the optimized processing conditions. In this way, adding mesh to the polymeric matrix improves the strength and polymer / polymer bond in the sandwich structure. Placing the mesh in the sandwich structure converts the brittle behavior of the polymeric...
Grain Size Control in Fusion Welding and Wire-Arc Additive Manufacturing of Ferritic Stainless Steels
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor) ; Kokabi, Amir Hossein (Supervisor)
Abstract
Ferritic stainless steels, despite having a good combination of mechanical properties and corrosion properties and low price, are less used than austenitic stainless steels due to their low weldability. The main challenges of welding ferritic stainless steels are coarse grain formation in the molten area as well as grain growth in the heat affected zone. In this research, in the first phase, an attempt is made to change the shape and size of the grains in the melted zone by changing the GTAW fusion welding parameters, including welding current and welding speed. In the second phase, an attempt is made to prevent the formation of columnar grains by adding micron particles to the molten pool...
Microstructure and Mechanical Properties of Two-step TLP Bonded 304 Stainless Steel with a Cobalt base Interlayer
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor) ; Ekrami, Aliakbar (Supervisor)
Abstract
Considering the wide applications of 304 stainless steel in various industries and the existing literature on transient liquid phase bonding of stainless steels with a variety of interlayers, the present work aimed to reduce the bonding time by using a two step bonding method. Faster bonding reduces both energy consumption during bonding and the base metal grain growth. It also leads to a lower reduction in the base metal and joint strength.Due to the melting point of the interlayer, different durations and a temperature of 1200°C were selected for the first step. This temperature was maintained for a specified period of time before it sharply dropped to and remained at 1180°C (the...