Showing 126 results for Tin
J. Saaedi, H. Arabi, Sh. Mirdamadi, Th. W. Coyle,
Volume 5, Issue 4 (12-2008)
Abstract
Abstract: Two different coating microstructures of Ni-50Cr alloy were obtained on a stainless steel substrate by
changing combustion characteristics of a high velocity oxy-fuel (HVOF) process and the size distribution of feed
powder during coating process. Use of the finer feed powder and leaner fuel in oxygen/fuel ratio (i.e. using a ratio
much less than stoichiometric ratio) led to formation of an extremely dense coating with high oxide content. Heat
treating of this coating at 650ºC for 4 hours caused the formation of an intermetallic sigma phase having Cr7Ni3
stoichiometry. Formation of this phase has been reported occasionally in thin films not in thermal spray coatings, as
reported for the first time in this research. In addition no sigma phase was detected in the HVOF as-deposited coating
with low oxide content after heat treatment of the samples. Therefore, due to the limited number of papers available in
the subject of formation of phase in either Ni-Cr bulk alloys or coatings, it is considered appropriate to show up a
case in this field. In this work, the formation of sigma phase in Ni-50Cr coating deposited by HVOF technique and
heat treated at 650ºC was discussed and then the coating was characterized.
A.nouri, Sh.kheirandish, H. Saghafian,
Volume 5, Issue 4 (12-2008)
Abstract
Abstract: In the current work, the strain hardening behavior of dual-phase steels with different silicon content (0.34-
2.26 Wt. %) was examined using the modified Crussard-Jaoul analysis. It was shown that these dual-phase steels
deform in two stages over a uniform strain range. Each stage exhibited a different strain hardening exponent varying
with silicon content. At the first stage, work hardening exponent remind significantly constant, while during the second
stage, it decreased with increasing silicon content from 0.34% to 1.51% and then increased for the higher silicon
contents (1.51% to 2.26%). It was found that the strain hardening behavior of these steels was predominantly affected
by the volume fraction of martensite at low silicon contet and the ferrite strengthening induced by silicon at the higher
silicon content. The effect of silicon content on the volume fraction of martensite and tensile properties were also
considered.
H. Aghajani, M. Soltanieh, F. Mahboubi, S. Rastegari and Kh. A. Nekouee,
Volume 6, Issue 1 (3-2009)
Abstract
Abstract: Formation of a hybrid coating by the use of plasma nitriding and hard chromium electroplating on the
surface of H11 hot work tool steel was investigated. Firstly, specimens were plasma nitrided at a temperature of 550
°C for 5 hours in an atmosphere of 25 vol. % H2: 75 vol. % N2. Secondly, electroplating was carried out in a solution
containing 250 g/L chromic acid and 2.5 g/L sulphuric acid for 1 hour at 60 °C temperature and 60 A/dm2 current
density. Thirdly, specimens were plasma nitrided at a temperature of 550 °C for 5 and 10 hours in an atmosphere of
25 vol. % H2: 75 vol. % N2. The obtained coatings have been compared in terms of composition and hardness. The
compositions of the coatings have been studied by X-ray diffraction analysis. The surface morphology and elemental
analysis was examined by using scanning electron microscopy. The improvement in hardness distribution after third
step is discussed in considering the forward and backward diffusion of nitrogen in the chromium interlayer. Also, the
formed phases in the hybrid coating were determined to be CrN+Cr2N+Cr+Fe2-3N+Fe4N.
I. Ebrahimzadeh, Gh.h. Akbari,
Volume 6, Issue 1 (3-2009)
Abstract
Abstract: Horizontal continuous casting is widely used to produce semi-finished and finished metallic products.
Homogeneity in metallurgical characteristics and mechanical properties in such products is of importance. In the
present work microstructure and mechanical properties of a horizontal continuous cast pipe have been studied.
Microstructural features were investigated by an optical microscope equipped with image analyzer and SEM was used
to characterize precipitates. Tensile behavior, impact strength and hardness variations were the mechanical properties
which were studied. Results showed that microstructure and mechanical properties had diversities in different parts of
the pipe and distinct differences were observed between upper and lower parts of the pipe. A meaningful correlation
was found in microstructure and mechanical properties in different parts of the component.
H. Mohammadzade, Sh. Kheirandish, H. Saghafian,
Volume 6, Issue 2 (6-2009)
Abstract
Abstract:
transition and heat affected zones formed during surface remelting (in order to improve wear resistance) with TIG
process has been investigated. Relationship between various TIG parameters and thickness of remelted and heat
affected zones revealed that a high concentrated heat energy is imposed by TIG process which makes it a proper option
for focused surface treatment. Based on microstructural examinations five areas with different microstructure and
microhardness were identified within the surface area. Graphite flakes were totally dissolved within the first area
leading to the transformation of denderitic austenite to plate martensite and the formation of ledeburite within
interdenderites. The main feature of the second area, resulted from the presence of graphite flakes, was the local
melting with a gap in the vicinity of graphite flakes and that of third area was the formation of finer and denser
martensite plates closer to the graphite flakes compared with those formed at a further distance. In the fourth layer
there is a mixture of martensitic and pearlitic matrix while the matrix of fifth layer has no change of microstructure.
In this study the effect of graphite flakes present in a pearlitic grey cast iron on the microstructure of melted,
S. Zavareh, F. Majedi,, M. Sh. Sharif, F. Golestanifard,
Volume 6, Issue 3 (9-2009)
Abstract
Abstract: Multiwalled carbon nanotubes (MWCNTs) were coated with MgO nano particles using simple precipitationmethod. The growth of Mg(OH)2particles was controlled by adjusting the alkaline concentration, salt concentrationand feed rate in simple precipitation method. The nanometer-sized Mg(OH)2particles were precipitated on the surfaceof functionalized MWCNTs by reaction between MgSO4 solution and NH4OH. The samples have been characterizedby scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction and thermal gravimetricanalysis. The results showed a nominally complete MgO coating over the entire outer surface of MWCNTs resulting inimprovement of their oxidation durability.
A. H. Shafie Farhood, F. Akhlaghi,
Volume 7, Issue 1 (3-2010)
Abstract
Abstract:
structures in alloys. This method is based on pouring the melt through a small sized nozzle into a mould located at a
certain height under the crucible. This simple method generates globular structures without using equipments such as
impellers, electromagnetic stirrers, ultrasonic probes and cooling slopes. Therefore it is cost effective. In the present
study, the effect of casting size and mould casting modulus on the globular structure evolution in A356 aluminium alloy
specimens prepared by NMS process was investigated. The results showed that regardless of the different casting
modulus and their sizes, all the specimens exhibited globular structures. However, the size and shape factor of the
globules decreased with increased casting modulus and casting size indicating the influential effect of the surface area
of the mould in generating globular structures in this process.
Narrow Melt Stream (NMS) is a relatively new semisolid metal processing technique for producing globular
A.m. Rashidi, A. Amadeh,
Volume 7, Issue 2 (6-2010)
Abstract
Abstract:
nanocrystalline nickel samples with the grain size of ~25 nm were prepared via direct current electrodeposition and
aluminized for different durations by pack cementation method at 500
means of SEM, EDS and XRD techniques. According to results, short time aluminizing resulted in the formation of a
single aluminide layer whereas at long duration two distinct aluminide layers were formed. The growth kinetics of the
coating was non-parabolic at short times while it obeyed the parabolic law at long duration. The parabolic growth
rate constant of single phase coating formed on electrodeposited samples was about 30 ìm / h1/2 approximately 3 times
greater than the data reported for coarse grained nickel (8.4 ìm / h1/2). Meanwhile, the overall growth rate constant
was decreased to 11.7 ìm / h1/2, when double aluminide layers formed on nanocrystalline nickel.
In this research, aluminizing behavior of ultra fine-grained nickel was investigated. For this purpose,oC. The aluminide layers were examined by
A. Jafaria, S. H. Seyedeina, M. R. Aboutalebia, D. G. Eskinb, L. Katgermanb,
Volume 7, Issue 3 (8-2010)
Abstract
ABSTRACT Macrosegregation has been received high attention in the solidification modeling studies. In the present work, a numerical model was developed to predict the macrosegregation during the DC Casting of an Al-4.5wt%Cu billet. The mathematical model developed in this study consists of mass, momentum, energy and species conservation equations for a two-phase mixture of liquid and solid in an axisymmetric coordinates. The solution methodology is based on a standard Finite Volume Method. A new scheme called Semi-Implicit Method for Thermodynamically-Linked Equations (SIMTLE) was employed to link energy and species equations with phase diagram of the alloying system. The model was tested by experimental data extracted from an industrial scale DC caster and a relatively good agreement was obtained. It was concluded that a proper macrosegregation model needs two key features: a precise flow description in the two-phase regions and a capable efficient numerical scheme
Z. Ghaferi, K. Raeissi, M. A. Golozar,, A. Saatchi, S. Kabi,
Volume 7, Issue 4 (10-2010)
Abstract
Abstract:
current densities. Electrochemical impedance spectroscopy (EIS) results showed that the codeposition mechanism of
tungsten in Ni-W deposition is the reduction of tungsten oxide which changed to the reduction of tungsten-containing
ion complexes at higher current densities. In Co-W electrodeposition, the tungsten codeposition takes place via
reduction of tungsten oxide, although, the role of tungsten-containing complexes at higher current densities cannot be
ruled out. The surface morphology of Ni-W coatings was crack-free and was strongly dependent on deposition current
density. In addition, higher grain size and lower tungsten content were obtained by increasing the current density. In
Co-W coatings, no obvious variation in surface morphology was observed except for the fine cracks appeared at
higher current densities. In this system the grain size remained almost constant with increasing current density. The
microhardness values of Ni-W and Co-W coatings decreased due to the increase in the grain size and/or decrease in
tungsten content.
Ni-W and Co-W alloy nanocrystalline coatings were electrodeposited on copper substrate at different
N. Eslami Rad*, Ch. Dehghanian,
Volume 7, Issue 4 (10-2010)
Abstract
Abstract: Electroless Nickel (EN) composite coatings embedded with Cr2O3 and/or MoS2 particles were deposited to combine the characters of both Cr2O3 and MoS2 into one coating in this study. The effects of the co-deposited particles on corrosion behavior of the coating in 3.5% NaCl media were investigated. The results showed that both Ni-P and Ni-P composite coatings had significant improvement on corrosion resistance in comparison to the substrate. Codeposition of Cr2O3 in coating improved corrosion characteristic but co-deposition of MoS2 decreased corrosion resistance of the coating.
S. H. Razavi, Sh. Mirdamadi, M. M. Hormozi,
Volume 8, Issue 1 (3-2011)
Abstract
Abstract: The aim of the present investigation is to study the physical and mechanical characteristics of dental-filling spherical high-copper and silver amalgams and to compare them with a common high-copper domestic unicompositional amalgam. In this study, cylindrical specimens were mechanically condensed according to the ISO 1559:1986 Standard in order to measure the compressive strength, Vickers hardness, static creep and dimensional change on setting. Adding more silver to the amalgam increased its compressive strength, creep resistance and reduced mercury vapor. After 1, 24 and 168h of amalgamation and Modulus of elasticity of specimen S1, the mean hardness and compressive fracture strength were significantly lower than those of . No significant differences were identified for the two alloys in the creep and dimensional changes on setting. It can be concluded that as far as the mechanical properties or corrosion resistance is concerned, the amalgam should be comprised of at least one spherical alloy.
P. Samadi, M. Reza Afshar, M. R. Aboutalebi, S. H. Seyedein,
Volume 9, Issue 1 (3-2012)
Abstract
Electrochemical coating processes are significantly affected by applied magnetic fields due to the generation of electromagnetic forces. The present research work has been undertaken to study the effect of coating parameters such as current density and alumina concentration on the characteristics of Ni-Al2O3 composite coating under static magnetic field. Ni-Al2O3 composite coating was applied on a mild steel substrate using conventional Watts solution containing Al2O3 particles with and without magnetic field. The coating microstructure and Al2O3 particle density in the coating layer were examined by scanning electron microscopy (SEM). It was found that the applied magnetic field made the coating structure finer and leads to the increases of the particle content in the coating. However, the results confirmed that the magnetic forces inversely affected the particle density in the coating at higher current density than that of normal coating process.
W. Orlowicz, M. Tupaj, M. Mróz, J. Betlej, F. Ploszaj,
Volume 9, Issue 1 (3-2012)
Abstract
Abstract: This study presents the research results of effect that refining process has on porosity and mechanical properties of high pressure die castings made of AlSi12S alloy. The operation of refining was carried out in a melting furnace with the use of an FDU Mini Degasser. Mechanical properties (UTS, YS, Elongation, Brinell Hardness) were assessed on samples taken from high pressure die castings. The effect of molten metal transfer operation and the time elapsing from completion of the refining process on the alloy mechanical properties was determined.
Mr. Hossein Minouei, Dr. Mohammadhossein Fathi, Dr. Mahmood Meratian, Mr. Hossein Ghazvinizadeh,
Volume 9, Issue 3 (9-2012)
Abstract
ASTM F-75 Cobalt-base alloy castings are widely used for manufacturing orthopedic implants. This alloy needs both homogenization and solutionizing heat treatment after casting, as well as bioactivation of the surface to increase the ability of tissue bonding. In this study, ASTM F-75 Cobalt-base substrate was heat treated at 1220°C for 1 hour in contact with Hydroxyapatite-Bioglass powder in order to solutionize and homogenize the microstructure and promote surface bioactivation. For bioactivity evaluation, heat treated specimens were immersed in Simulated Body Fluid (SBF). Surface of specimens before and after the immersion was analyzed by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX) and X-Ray Diffraction (XRD). Results showed an appropriate microstructure with bioactive layer on the surface of specimens after heat treatment. In vitro result and formation of bone-like apatite layer on specimens indicated that heat treated samples were potentially suitable for bone replacement and tissue regeneration under highly loaded conditions.
M. Alipour, S. Mirjavadi, M. K. Besharati Givi, H. Razmi, M. Emamy, J. Rassizadehghani,
Volume 9, Issue 4 (12-2012)
Abstract
In this study the effect of Al–5Ti–1B grain refiner on the structural characteristics and wear properties of Al–12Zn–3Mg–2.5Cu alloy was investigated. The optimum amount for Ti containing grain refiners was selected as 2 wt.%. T6 heat treatment, (i.e. heating at 460 °C for 1 h before water quenching to room temperature and then aging at 120 °C for 24 h) was applied for all specimens before wear testing. Dry sliding wear resistant of the alloy was performed under normal atmospheric conditions. The experimental results showed that the T6 heat treatment considerably improved the resistance of Al–12Zn–3Mg–2.5Cu alloy to dry sliding wear.
Z. Shahri, S.r. Allahkaram,
Volume 9, Issue 4 (12-2012)
Abstract
Metal matrix composite coatings reinforced with nano-particles have attracted scientific and technological interest due to the enhanced properties exhibited by these coatings. Cobalt/hexagonal boron nitride nano-composite coatings were prepared by means of the pulse current electroplating from a chloride electrolyte on copper substrates and a comparison was made with the pure cobalt in terms of structure and tribological properties. Effects of particles concentration (5-20 gL-1) and current density (50-200 mA cm-2) on the characterization of electroplated coatings were investigated via X-ray diffraction analysis, energy dispersive spectroscopy and Vickers micro-hardness. Moreover, the tribological behavior was studied using pin-on-disc method. The results showed that cobalt/hexagonal boron nitride nano-composite coatings have higher hardness, wear resistance and lower friction coefficient than pure cobalt and the plating parameters strongly affect the coating’s properties
M. Alzamani, A. Shokuhfar, E. Eghdam, S. Mastal,
Volume 10, Issue 1 (3-2013)
Abstract
Abstract:In the present research, SiO2–TiO2 nanostructure films were successfully prepared on windshields using the sol–gel technique for photocatalytic applications. To prevent the thermal diffusion of the sodium ions from the glass to TiO2 films, the SiO2 layer was pre-coated on the glass by the sol–gel method. The substrates were dipped in the sol and withdrawn with the speed of 6cm/min-1 to make a gel coating film. The coated films were dried for 2 days at 27 °C to allow slow solvent evaporation and condensation reactions due to rapid sol–gel reaction of Titania precursor. Then, the films were annealed at 100 °C for 30min and at the final temperature (500, 700 °C) for 30 min continuously. The structure and surface morphology properties, which are as a function of annealing temperature, have been studied by SEM FE-SEM and XRD. The FE-SEM surface morphology results indicate that the particle size increases from 19 to 42 nm by increasing the annealing temperature from 500 °C to 700 °C. Likewise, XRD illustrate the crystal anatase and rutile as main phases for TiO2-SiO2 films annealed at 500 °C and 700 °C respectively. This procedure resulted in transparent, crack-free SiO2–TiO2 films.
H. Arabi, S. Rastegari, V. Ramezani, Z. Valefi,
Volume 10, Issue 2 (6-2013)
Abstract
The objectives of this research were to find an economical way of reducing porosities in the microstructure of coatings deposited by flame spraying technique on CK45 steel and also trying to increase their cohesive strength to the substrate, so that the overall wear properties of this type of coating can be improved. So several specimens from this steel coated with NiCrBSi powder under specific conditions were subjected to various furnace heat treatment at 1000, 1025, 1050, 1075 and 1100 °C, each for periods of 5, 10 and 15 minute before cooling them in air. Tribological properties of treated coatings were evaluated by pin on disc method. The results show the highest wear resistance and microhardness values observed in one of the sample was due to lower amount of porosity and higher amount of very fine Cr2Ni3B6 particles precipitated homogeneously throughout its microstructure during specific heat treatment.
M. Bahamirian, Sh. Khameneh Asl,
Volume 10, Issue 3 (9-2013)
Abstract
In the present study NiCrAlY bond coating layer was produced by electroplating against common atmospheric plasma spraying (APS). Both types of the bond coats were applied on IN738LC base metal then, the YSZ (ZrO2-8% Y2O3) thermal barrier top layer was coated by atmospheric plasma spray technique. Hot corrosion is one of the main destructive factors in thermal barrier coatings (TBCs) which come as a result of molten salt effect on the coating–gas interface. In this investigation the hot corrosion behavior of coatings was tested in the furnace which was contain Na2SO4-55% V2O5 and mixed salts environment at 900°C up to 15 hr. dwell time. Optical microscopy, scanning electron microscopy (SEM / EDS) and X-ray diffraction analysis (XRD) was used to determine the crystallographic structure and phase transformation of the coatings before and after the hot corrosion tests. The transformation of tetragonal Zirconia to monoclinic ZrO2 and formation of YVO4 crystals as hot corrosion products caused the degradation of mentioned TBCs. The results showed NiCrAlY coated by economical electroplating method a viable alternative for common thermals sprayed bond coats in hot corrosive environments with same corrosion behavior
