Showing 34 results for Steel
Seyed M. Ahl Sarmadi, M. Shamanian, H. Edris, M. Atapoor, A. Behjat, M. Mohtadi Bonab, J. Szpunar,
Volume 36, Issue 1 (6-2017)
Abstract
Super duplex stainless steel is a kind of duplex stainless steel that has pitting resistant equivalent number over than 40. Unified Numbering System (UNS) S32750 is a common super duplex stainless stee, that is mostly applied in oil and gas refinery industries, because of its proper corrosion-resistant properties . Therefore, joining of these steels by welding is very important, but the greatest problem in this regard is the corrosion and decrease in mechanical properties after welding.. In this research, UNS S32750has been joined by friction stir welding method. The tool being used in this research was a WC with 16mm shoulder diameter, 5 mm pin diameter, and 1.9 mm height. X-ray diffraction showed that harmful phases, such as sigma or chi have not been formed. Microstructure study indicated that grain size in the stir zone has decreased. Vickers Hardness Test Method has been applied on welded samples. Moderate microhardness of base metal was 285 Vickers but, the microhardness increased in the stir zone to 360 Vickers, because of decreasing the grain size. The cyclic polarization determined that potential and corrosion current of joint metal by friction stir welding method was similar to base metal. Also, it was revealed that ferrite percentage in the stir zone doesn't decrease very much because the friction stir welding heat input is very low and the colding rate is very high.
Kh. Farjam Hajiagha, A. R. Akbari, R. Mohammadzadeh,
Volume 36, Issue 2 (9-2017)
Abstract
In this study, the kinetics of austenite layer growth on the surface of Fe-23Cr-2.4Mo ferritic stainless steel during solution nitriding and the effects of nitrogen adding on microstructure and hardness of the steel have been investigated. Steel plates of 2 mm thick were solution-nitrided at 1200˚C under nitrogen pressure of 0.25 MPa for 2, 3, 6, 9, 12 hours. Microstructure, the thickness of austenite layer and the hardnes of the nitrided samples, were investigated by using optical microscope, X-ray Diffraction (XRD) and microhardness measurements. The results showed that during solution nitriding, nitrogen diffuses through the lattice and grain boundaries and transforms ferrite to austenite phase, with average nitrogen diffusion coefficient of 6.54×10-5 mm2s-1. The thickness of the austenite layer formed on the samples surfaces increased proportional to the square root of the nitriding time, so that after 12 hours niriding, the whole thickness of the ferritic sample with hardness of 262 HV0.1 transformed to austenite with hardness of 420 HV0.1.
Mr S. A. Razavi, Mr S. F. Ashrafizadeh,
Volume 36, Issue 2 (9-2017)
Abstract
Age hardening processes cause a wide range of changes in 17-4 PH stainless steel properties. Aging at 480ºC for 1 hour (A480-1) and aging at 620ºC for 4 hours (A620-4) are two most applicable heat treatment processes for this alloy. Not only the studies on fatigue behavior of this alloy in these two heat treatment conditions are few, but also the methods of fatigue test were mostly axial. In this study, after microstructure studies, hardness and tension tests, fatigue behavior at A480-1 and A620-4 conditions were evaluated by using a rotational bending fatigue test machine. Tension results showed that yield strength and ultimate tensile strength of A480-1 specimens were 40 percent more than A620-4 specimens. However, elongation of A620-4 specimens was 30 percent more than A480-1 specimens. Fatigue results revealed the endurance limit of aged specimens is 50 MPa more than overaged specimens. Overall results showed that A480-1 condition specimens are more resistant to fatigue than A620-4 condition specimens.
M. Poorkabirian, H. Mostaan, M. Rafiei,
Volume 36, Issue 2 (9-2017)
Abstract
In this research, dissimilar welding between 4130 low alloy steel and austenitic stainless steel 316L has been investigated using Gas Tungsten Arc Welding (GTAW). Two types of filler metals, including ERNiCr-3 and ER309L, were used for this purpose. Moreover, the joint microstructures including the weld metals, heat affected zones and interfaces were characterized by optical and Scanning Electron Microscopy (SEM). The mechanical behavior of the joint was tested by impact and tension tests. Observations by SEM showed that in impact test, the fracture is soft. In the tensile test, the welded sample by ER309L filler metal was fractured from 316L base metal, but welded specimen with ERNiCr-3 was fractured from welded zone. Also, the results showed a dendritic structure in the nickel-based weld metal. No crack was found in the cellular-dendritic microstructure of ER309L weld metal due to the existance of delta ferrite between them.
H. Chavilian, K. Farmanesh, A. Soltanipour, E. Maghsoudi,
Volume 36, Issue 3 (11-2017)
Abstract
In this research, industrial hot deformation processes was simulated for 321 austenitic stainless steel using hot compression test with the aim of acquiring technical knowledge and indigenization of stainless steel production. The obtained stress-strain curves showed the common retrieval dynamic behaviour. By microscopic studies, the main restoration mechanism during hot deformation in this steel was diagnosed as dynamic recrystallization, that due to low stacking fault energy of 321 stainless steel, this phenomenon was justified. Then, using diagrams related to real stress, real strain and strain rate, the onset point of dynamic recrystallization was determined under different conditions. Also, using the constitutive equations and Zener-Holloman parameter, hot deformation behaviour of 321 stainless steel was studied and the activation energy of hot deformation for this steel was determined as 422 (Kj/mol).
Sh. Tavakoli Dehaghi, S. Darvishi, Sh. Nemati, M. Kharaziha,
Volume 37, Issue 3 (12-2018)
Abstract
Abstract: With the advances in the development of biomaterials for tissue replacement, the attention of scientists has been focused on the improvement of clinical implant properties. In this regard, despite the appropriate properties of the stainless steel, the application of stainless steel as implants has been limited due to the weak corrosion resistivity. The purpose of this paper was preparation and characterization of hydrophobic polydimethylsiloxane (PDMS)-SiO2-CuO nanocomposite coating on the 316L stainless steel surface. The 316L stainless steel was coated by SiO2 nanoparticles (20 wt. %), CuO nanoparticles (0.5, 1 and 2 wt. %) and biocompatible PDMS. In this research, x-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied to characterize the coating. Moreover, the roughness and water contact angle of the coatings consisting of various amounts of CuO nanopowder were estimated. Finally, the effects of various amounts of the CuO nanopowder on the corrosion resistivity of nanocomposite coatings were investigated. XRD patterns confirmed the presence of crystalline CuO nanoparticles on the substrate. Due to the non-crystalline nature of silica nanoparticles and the semi-crystalline PDMS polymer, no peak confirming the presence of these phases was detected on the XRD pattern of the nanocomposite coating. SEM images showed the formation of a lotus leaf-like layer on the surface of the nanocomposite coating containing 1 and 2 wt. % CuO. Moreover, water contact angle evolution revealed that while contact angle was 81 degree without CuO nanoparticles, it was enhanced to 146 degree in the presence of 1 wt. % CuO. Moreover, the corrosion study showed the nanocomposite containing 2 wt.% CuO had the best corrosion resistance, the corrosion current density of 2.1E-7 A.cm-2, and the corrosion potential of 0.22 V.
M. Mahmoudi Saleh Abad, M. Zandrahimi, H. Ebrahimi Far,
Volume 37, Issue 3 (12-2018)
Abstract
In order to improve the oxidation and hot corrosion resistance of steels, various elements including aluminum, chromium, silicon, titanium or combination of these elements can be diffused on to the surface of steel. In this study, aluminum and titanium were simultaneously co-deposited onto the AISI 430 ferritic stainless steel substrate by the pack cementation process. Coating was examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The coating consised of two layers with the thickness of approximately 14 microns. The results obtained by XRD showed the existence of FeTi, TiO2, AlTi, Al3Ti and Al5Ti phases in the coating. Isothermal oxidation and cyclic oxidation were carried out at 1000○C. It was showed that the diffusional coating of aluminum-titanium led to the improvement of cycle and isothermal oxidation resistance.
M. Ghasemian Malakshah, F. Ashrafizadeh, A. Eslami, F. Fadaeifard,
Volume 38, Issue 2 (9-2019)
Abstract
Since martensitic precipitation hardened 17-4pH stainless steel has been widely used in corrosive environments, evaluation of its corrosion fatigue behavior is important. In this research, after microstructural studies, mechanical, corrosion, fatigue and corrosion fatigue tests were performed on 17-4pH specimens. Fatigue and corrosion fatigue tests were carried out at the stress ratio of -1 and the stress frequency of 0.42 Hz (to increase the effect of corrosive solution), and corrosion fatigue tests were conducted in 3.5% NaCl solution, an environment similar to corrosive sea water. Fatigue limit of 17-4pH stainless steel was 700 MPa in air and 415 MPa in corrosive environment. Comparing the S-N curves of this alloy at the optimal heat treatment cycle in two modes of fatigue and corrosion fatigue revealed the reduction of fatigue limit up to 40 % in the presence of corrosive environment. This reduction was due to the effect of observed corrosion pits on the surface and Damaged passive layer.
H. Ebrahimifar, M. Zandrahimi, F. Ekhlaspour,
Volume 38, Issue 3 (12-2019)
Abstract
One of the most effective ways to improve oxidation resistance of interconnects used in solid oxide fuel cells (SOFCs) is to apply a layer of conductive protective coating. In this study, Crofer 22APU ferritic steel was coated in a titanium- based powder mixture by pack cementation method. The powder composition for titanium coating was Ti 20 wt.%, NH4Cl 5 wt.% (activator) and Al2O3 75 wt.%. The optimum temperature and time to obtain the best coating quality in terms of adhesion and porosity were 800 °C and 7 hours, respectivly. The obtained titanized coating consisted of TiFe, TiFe2 and TiCr2 phases. The results of isothermal and cyclic oxidation tests carried out at 900 °C, showed that titanium-coated samples had better oxidation resistance than non-coated samples. Microstructural and phase studies of coated and oxidized samples were performed by scanning electron macroscopy (SEM) and X-ray diffraction analysis (XRD). During oxidation process, the coating layer was converted into TiFe, TiFe2, TiFe2O5, TiO2 and TiCr2O4 phases. The coated specimens had lower weight gains relative to uncoated samples showing that coating effectively protects the substrate against oxidation. Moreover, coated samples had higher electrical resistance than uncoated ones.
M. H. Musazadeh, R. Vafaei, E. Mohammad Sharifi, Kh. Farmanesh,
Volume 38, Issue 3 (12-2019)
Abstract
Finite element (FE) simulations in conjunction with experimental analysis were carried out to characterize the deformation behavior of an AISI 321 austenitic stainless steel (ASS) during cold pilgering process. The effect of process parameters including feed rate (4 and 8 mm) and turn angle (15, 30 and 60°) on damage build-up were also evaluated. The Johnson-cook model was used to simulate the flow behavior of material. By considering compressive stresses, a new revised Latham-Cockcraft damage was calculated and used to determine the optimum process parameters. It was found that the radial and hoop strains in all friction conditions were compressive, while the axial strains were observed to be tensile. The amount of strain (whether it is compressive or tensile strain) was also higher on the outside of the tube compared to its inside. By considering fatigue cycles of a tube element during the process, the feed rate of 8mm, turn angle of 60° and the lowest coefficient of friction were determined as optimum parameters.
M. Jafari, M. Rafiei, H. Mostaan,
Volume 39, Issue 2 (8-2020)
Abstract
In this research, the effect of temperature and time on the properties of AISI420/SAF2507 dissimilar joint produced by transient liquid phase bonding process was investigated. A BNi-2 interlayer with 25 μm thickness was inserted between two dissimilar steel samples. The bonding process was performed at 1050 oC and 1100 oC for different bonding times. The microstructures of the joints were studied using optical microscope, scanning electron microscope and energy dispersive X-ray spectroscopy. Microhardness and tensile shear strength of bonded samples were investigated. Isothermal solidification was completed for the joints bonded at 1050 oC and 1100 oC for 45 min and 30 min, respectively. ASZ and ISZ areas of the bonding zone at the bonding temperature of 1050 oC indicated the highest (520 HV) and the lowest (300 HV) microhardness values, respectively. Sample bonded at 1050 oC for 1 min indicated the lowest tensile strength (196 MPa) and sample bonded at 1100 oC for 60 min indicated the highest tensile strength (517 MPa).
S. Asghari, A. M. Eslami, A. Taheri Zadeh, N. Saeidi,
Volume 39, Issue 3 (12-2020)
Abstract
In this study, the effect of welding heat input on microstructure and mechanical properties of dissimilar joints of API-X42 and API-B pipeline steels was investigated. Evaluation of the microstructures showed that increasing the welding heat input decreased acicular ferrite in weld metal microstructure, while amount of Widmanstatten ferrite, polygonal ferrite and grain boundary ferrite increased. Also, results of microhardness test showed that by increasing the heat input, hardness of weld metal and the heat affected zone decreased. Tensile test results showed that as the heat input increased, fracture transferred from base metal of API-B to the heat affected zone. Impact test results also showed that increasing the welding heat input could sharply drop the impact energy of the heat affected zone for both base metals due to extensive grain growth.
F. Mostafaee Heydarloo, M. Morakabati, H. Badri ,
Volume 39, Issue 3 (12-2020)
Abstract
The aim of this study was to investigate the suitable temperature range for hot deformation of three medium carbon Ni-Cr-Mo low alloy steels by hot tensile and hot torsion tests. Hot tensile tests were carried out in the te,prature range of 850-1150°C at a constant strain rate of 0.1 s-1 until fracture. Then, the tensile flow behavior, hot ductility and microstructural evolution of the steels were studied. Hot torsion tests were performed in the temperature range of 1200-780°C at strain of 0.1 with strain rate of 1s-1. The effect of titanium and niobium on the mean flow stress and the non-recrystallization temperature were investigated. The tensile test results showed that dynamic recrystallization was the dominant mechanism at temperatures above 950°C in the base steel and temperatures above 1050°C in the microalloyed steels. The results of hot torsion tests showed that the non-recrystallization temperatures of the base, Ti containing and Nb containing steels were 1070°C, 1069°C and 1116°C, respectively. Finally, the suitable hot deformation temperature range to achieve optimum mechanical properties in the base and Ti containing steels obtained as 950-1070°C and that of Nb containing steel obtained as 950-1100°C.
R. Moradi, M. Roshanaee, H. Mostaan, F. Nematzadeh, M. Safari,
Volume 40, Issue 1 (5-2021)
Abstract
In this research, microstructure and mechanical properties of laser welded joints between 2304 duplex stainless steel and Inconel 718 nickel-based super alloy were investigated. Microstructural evolution in the various areas of welded joints and also the effect of welding parameters on the mechanical properties of dissimilar joints were studied. Response surface methodology based on the central composite design was used in order to find the optimum welding parameters. Effective parameters of the welding process including laser power, travel speed and defocusing distance were set in the range of 1000 to 1900 W, 1 to 5 mm/s and -1 to 1 mm, respectively. Uniaxial tensile test was used to evaluate the fracture force of weld joints. The microstructural observations and phase evolutions were studied using optical microscope. It was found that the fracture force of the weld joints firstly increased by travel speed and defocusing distance and then decreased by further increase. The maximum fracture force was obtained when laser power, travel speed and defocusing distance were 1900 W, 3 mm/s and 0 mm, respectively. The center line of weld metal was mainly consisted of equiaxed grains where, columnar grains were formed in the fusion line. The obtained results from the hardness measurement showed that the hardness of Inconel 718 was decreased due to dissolution of TiC and NbC particles.
R. Amirarsalani, M. Morakabati, R. Mahdavi,
Volume 40, Issue 1 (5-2021)
Abstract
In this research, the hot deformation behavior of W360 tool steel was investigated using hot compression test at 1000-1200°C and strain rates of 0.001, 0.01, 0.1, and 1 s-1. According to the results, dynamic recrystallization was found the most important restoration factor of this alloy during hot deformation. Recrystallization was enhanced with an increase in temperature and strain rate. Also, the hot working process was optimized by drawing the processing map of this steel. Microstructural images obtained from the hot compression test showed that recrystallization started at 1000°C and the strain rate of 0.01 s-1 and developed with increasing temperature and strain rate due to an increase in the stored energy and suitable regions for nucleation. The results of drawing the processing map showed that the best hot deformation region was the temperature range of 1050-1150°C and strain rates of 0.1-1 s-1.
M. Khosravi , M. Mansouri, A. Gholami, Y. Yaghoubinezhad,
Volume 40, Issue 1 (5-2021)
Abstract
In this research, the effect of graphene oxide (GO) and reduced graphene oxide (RGO) nanosheets on the mechanical and microstructural properties of AISI 304 stainless steel welded joints produced by the flux-cored arc welding (FCAW) method was investigated. Light microscope, field emission scanning electron microscope (FE-SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), Raman spectroscopy, and tensile strength test were used to characterize the samples. GO was synthesized by modified Hummers’ method and reduced by hydrazine. Accordingly, the pastes of GO and RGO in different concentrations of 1, 3, and 10 mg/ml were applied in the groove. The results demonstrated that increasing the RGO concentration up to 10 mg/ml improves the tensile strength and hardness values of welded joints up to 23% and 43%, respectively. It seems that RGO nanosheets have a significant effect on the mechanical properties of the welded joints by pinning of dislocations.
M. Kamali Ardakani , M. Morakabati,
Volume 40, Issue 2 (9-2021)
Abstract
The aim of this study was to investigate the behavior of hot deformation and occurrence of restoration phenomena during the deformation of AISI H10 hot work tool steel. For this purpose, hot tensile test was performed on the steel in the temperature range of 900-1150 ºC with a temperature interval of 50 ºC and at a constant strain rate of 0.1s-1. The microstructures were examined and the curves of hot flow and ductility were drawn. According to the curves and microstructures, ductility was lower at temperatures of 900 ºC and 950 ºC due to inactivity of repair processes and the presence of carbides. Ductility increased in the temperature range of 1000-1100 ºC due to the occurrence of dynamic recrystallization. Finally, ductility decreased in the temperature of 1150 ºC due to the dissolution of carbide particles and grain growth. The results obtained from hot tensile test and microstructural studies at a constant strain rate of 0.1s-1 revealed that the appropriate temperature range for deformation of AISI H10 hot work tool steel was 1000-1100 ºC.
M. Salehi, M. Eskandari, M. Yeganeh,
Volume 40, Issue 2 (9-2021)
Abstract
In this study, microstructural changes in the thermomechanical processing and its effect on the corrosion behavior of 321 austenitic stainless steel were investigated. EDS analysis and optical microscopy were used to identify precipitates and microstructure, respectively. To evaluate the corrosion properties, potentiodynamic polarization test and electrochemical impedance spectroscopy were performed. First, the as-received sample was subjected to cold rolling with a 90% thickness reduction at liquid nitrogen temperature, and then annealing was performed at temperatures of 750, 850, and 1050 °C for 10 min. The results showed that severe cold rolling slightly improved the corrosion properties and in annealed samples, the corrosion resistance increased with more uniform microstructure, more reversion of martensite phase to austenite, and reduction of grain size. Annealed samples at 850 °C and 1050 °C with polarization resistance values of 8.200 kΩ.cm2 and 3.800 kΩ.cm2 depicted the highest and lowest corrosion resistance compared to other samples, respectively.
M. H. Rezvani, M. Yeganeh, S. M. Lari Baghal,
Volume 41, Issue 1 (8-2022)
Abstract
In this study, the addition of organic methionine inhibitor (as an eco-friendly inhibitor) to 0.1 M sulfuric acid media on corrosion resistance of 316L austenitic stainless steel (fabricated by rolling method and three-dimensional (3D) printing method) was investigated. Open-circuit potential electrochemical test and impedance, and structural tests such as optical and electron microscopy and x-ray photoelectron spectroscopy were conducted. The results showed that the corrosion resistance in the presence of inhibitor was higher than the sample without inhibitor and the inhibitory efficiency of methionine was increased up to 64% and the resistance to surface transfer between metal oxide and electrolyte was improved up to 2.77 times. The addition of methionine reduced the surface roughness and accumulation of the surface cavities. The chemical and physical adsorption mechanism of the inhibitor (negatively charged side adsorption of the methionine molecule with positively charged anodic regions of the metal surface) occurred at all points on the surface of the sample with the inhibitor. Also, the amount of oxygen in the cavities was reduced and the distribution of sulfur was uniform. The thickness of the passivator oxide layers was calculated more than the sample without inhibition due to the addition of inhibitor.
M. Ghalambaz, M. Shamanian, A. M. Eslami, M. Abdollahi, E. Abdoulvand,
Volume 41, Issue 1 (8-2022)
Abstract
This research investigated the bonding properties of AISI 321 austenitic stainless steel from microstructural, mechanical, and corrosion points of view. To obtain the optimal parameters of pulsed current gas tungsten arc welding (PCGTAW), the Taguchi method was used. A cyclic potentiodynamic polarization test evaluated the corrosion resistance of the welded samples. The optimal conditions were achieved when the background current, the pulse current, the frequency, and the percentage of the pulse on time were 50 amps, 140 amps, 5 Hz, and 50, respectively. On the other hand, the analysis of variance showed that the percentage of pulse on time equal to 36 and the background current equal to 46 amperes were the most influential factors on the surface current density of the austenitic stainless steel 321 connection using the PCGTAW process. The mechanical properties were assessed using punch shear testing. In the optimal condition, the maximum shear force and strength were 3200 N and 612 MPa, respectively. The results showed that the most critical factor affecting the bonding properties of 321 steel was the heat input.
