Showing 58 results for Steel
M. Soltanieh, M. Kiani, M. Hasheminiasari,
Volume 14, Issue 2 (6-2017)
Abstract
- The mechanism of diffusion layer growth in plasma nitrided coatings applied on a St52 steel using an active screen is investigated. The nitriding was performed at 450,500 and 550 ◦C temperature nitriding times of 5, 10 and 15 h, in a gas mixture containing 20 vol. % H2: 80 vol. % N2 and DC-pulsed plasma nitriding unit.
The surface, cross section and the thickness of diffusion of specimens was studied in terms of optical and scanning electron microscopy. According to the measurements of diffusion layer thickness, values of Q and D0 for nitrogen diffusion in substrate were calculated as 50585 (j/mol) and 4.11×10-10 (m2/s)respectively. The variations of depth of hardness during nitriding period was determined
H. Torkamani, H. Rashvand, Sh. Raygan, J. Rassizadehghani, Y. Palizdar, C. Garcia Mateo, D. San Martin,
Volume 14, Issue 3 (9-2017)
Abstract
In industry, the cost of production is an important factor and it is preferred to use conventional and low cost procedures for producing the parts. Heat treatment cycles and alloying additions are the key factors affecting the microstructure and mechanical properties of the cast steels. In this study an attempt was made to evaluate the influence of minor Mo addition on the microstructure and mechanical properties of conventionally heat treated cast micro-alloyed steels. The results of Jominy and dilatometry tests and also microstructural examinations revealed that Mo could effectively increase the hardenability of the investigated steel and change the microstructure features of the air-cooled samples. Acicular microstructure was the consequence of increasing the hardenability in Mo-added steel. Besides, it was found that Mo could greatly affect the isothermal bainitic transformation and higher fraction of martensite after cooling (from isothermal temperature) was due to the Mo addition. The results of impact test indicated that the microstructure obtained in air-cooled Mo-added steel led to better impact toughness (28J) in comparison with the base steel (23J). Moreover, Mo-added steel possessed higher hardness (291HV), yield (524MPa) and tensile (1108MPa) strengths compared to the base one.
A. Jafari Tadi, S.r. Hosseini, M. Naderi Semiromi,
Volume 14, Issue 3 (9-2017)
Abstract
Influence of formation of surface nano/ultrafine structure using deep rolling on plasma nitriding and tribological properties of the AISI 316L stainless steel was investigated. Initially, the deep rolling process was carried out on the bar-shaped specimens at 15 cycles with 0.2 mm/s longitudinal rate and 22.4 rpm bar rotation. Then, plasma nitriding treatment was applied on the as-received and deep rolled kinds at 450 °C and H2-25% Vol. N2 gas mixture for 5 h. Surface micro-hardness and un-lubricated pin-on-ring sliding wear tests were carried out on the as-received, deep rolled, plasma nitrided and deep rolled-plasma nitrided kinds. Results revealed that deep rolled-plasma nitrided kind is shown the highest wear resistance than the others, due to the further increased surface hardness achieved via the combined process.
M. Arockia Jaswin, D.m. Mohan Lal,
Volume 15, Issue 1 (3-2018)
Abstract
The behaviour of the cryogenically treated En52 martensitic valve steel has been experimentally analyzed in this paper. Material samples are subjected to deep cryogenic treatment after completing the regular heat treatment. The critical properties of the valve steel like wear resistance, hardness, tensile strength and impact strength are evaluated for the cryo treated En52 valve steel samples as per the ASTM standards. The microstructural changes and the mechanism behind the enhancement of the properties are examined and reported. The precipitation of fine carbides, transformation of retained austenite and refinement of carbides were the reasons behind the improvement of the mechanical properties. Deep cryogenic treatment process parameters are optimized for better wear resistance, hardness and tensile strength using grey Taguchi technique. Deep cryogenic treatment process greatly influences the wear resistance, a maximum enhancement of 54% is observed
R. Jafari, Sh. Mirdamadi, Sh. Kheirandish, H. Guim,
Volume 15, Issue 3 (9-2018)
Abstract
In this research, the objective was to investigate the stabilized retained austenite in the microstructure resulting from the Q&P heat treatment since the primary goal in Q&P is to create a microstructure consists of stabilized retained austenite and martensite. For this purpose, a low-alloy steel with 0.4wt. % carbon was treated by quench and partitioning (Q&P) process. The Q&P was conducted at different quench temperatures to obtain a considerable amount of retained austenite, while partitioning temperature and time were kept constant. Through analysis of the XRD profiles, volume percent, carbon concentration, and lattice parameters of retained austenite and martensite were calculated. At quench temperature equal to 160°C, 12vol.% austenite was stabilized to the room temperature, which was the highest amount achieved. The microstructural observations carried out on selected samples, revealed that retained austenite has a nanoscale particle size, about 200nm. Distinguishing retained austenite in the SEM micrographs became possible by utilizing SE2 signals via the difference in phases contrast. Two types of morphology, film-like and blocky type, were identified by means of TEM and TKD and a schematic model was proposed in order to explain these morphologies
S. Gholami Shiri, Y. Palizdar, . A. Jenabali Jahromi, Eduardo F. de Monlevade,
Volume 15, Issue 3 (9-2018)
Abstract
The relation between microstructure and the fracture mechanisms of δ-TRIP steel with different Nb-content has been investigated using complementary methods of light microscopy, SEM, EDS, EBSD, X-ray phase analysis and tensile test. The results revealed a close dependency between the presences of constitutive phases i.e. ferrite, bainite, retained austenite and martensite and the mode and characteristics of fracture. All samples revealed almost different fractography pattern which could be associated to the effect of Nb microalloying element. The different fractography patterns were consisted of dimple rupture, riverside and Wallner lines pattern. The proportion of the cleavage fracture in comparison of dimple rapture increased by increasing the Nb-content due to the increase of primary martensite in the microstructure.
M. Karimi Sahnesarayi, H. Sarpoolaky, S. Rastegari,
Volume 16, Issue 2 (6-2019)
Abstract
In this study nanosized TiO2coatings on the 316L stainless steel substrate were prepared by means of dip-coating technique in which thickness of the coating layer increased byrepeating the coating cycles in two different routes: (I) dipping and drying,respectively, were repeated one, three and five times and finally the dried coated sample was heat treated (single); (II) multiple heat treatment performed after each dipping and drying cycle, respectively.The structural, morphological and optical characterizations of coatings as well as thickness of coatings were systematically studied.The photocatalytic activity of the various TiO2 coatings was investigated based on the degradation of an aqueous solution of Methyl orange.Moreover, thecorrosion protective properties of coatings were evaluated in both dark and UV illumination conditions based on the obtained polarization curves. The results indicated 1.75 times improvement in photocatalytic reaction rate constant, a two orders of magnitude decrease in corrosion current density in dark condition and about 140 mV electrode potential reduction under UV illumination with optimum coating preparation procedure, repeating the cycle from dipping to heat treatment three times, than the sample prepared with one time coating and heat treatment since this procedure provided not only high thickness and defect-free coating but also transparent one.
H. Fathi, B. Mohammad Sadeghi, E. Emadoddin, H. Mohammadian Semnani,
Volume 16, Issue 3 (9-2019)
Abstract
Abstract
In the present research, the behavior of 304L austenitic stainless steel in the deep drawing process has been studied at the room temperature through experimental and finite element simulation method. Magnetic method calibrated by XRD was used to measure induced-martensite. Martensite volume fraction in the various portion of the deep drawn cup under optimum Blank Holder Force (BHF) and in the rupture location was evaluated. Findings of the present study indicated that higher martensite volume fraction occurred in the flange portion in the drawn cup due to higher strain and stress concentration in this area. Also, rupture happened at the arc portion of the wall of drawn cup with higher blank diameter due to higher strain, work hardening and martensitic transformation. Both experimental and simulation results showed that maximum LDR of 2 obtained in the forming process. All experimental procedures were simulated by LS-DYNA software, employing MAT_TRIP, and experimental results were in good agreement with the FE simulation.
M. Demouche, E. H. Ouakdi, R. Louahdi,
Volume 16, Issue 3 (9-2019)
Abstract
In this study, high-carbon, chromium alloy steel (100Cr6) having the initial spheroidized microstructure was welded using the rotary friction welding method. The effects of process parameters such as friction time and friction force were experimentally investigated. The friction welded joints were produced of two 100Cr6 steel rods. In order to examine the microstructure and mechanical properties of the friction welded 100cr6 steel joints, tensile and hardness tests were conducted. The microstructure of weld zone was examined by optical microscopy. It was found that after cooling, martensitic structure is obtained at the core and periphery of the weld joint. It was found that the tensile strength of friction welded samples is increased with increasing time and force of friction up to a certain level and then decreases again. Hardness measurements show a higher hardness at the centre of the weld joint in comparison with its periphery.
F. Hosseinabadi, A. Rezaee-Bazzaz, M. Mazinani, B. Mohammad Sadeghi,
Volume 17, Issue 1 (3-2020)
Abstract
An experimental–numerical methodology was used in order to study the microstructural effects on stress state dependency of martensitic transformation kinetics in two different TRIP800 low alloy multiphase steels. Representative volume elements extracted from actual microstructure have been utilized for simulating the mechanical behavior of mentioned steels. The mechanical behavior for each constituent phases required in the model has been taken out from those reported in the literature. A stress invariant based transformation kinetics law has been used to predict the martensitic phase transformation during deformation. Crystallographic and thermodynamic theories of martensitic phase transformation have been utilized for estimating the constant parameters of the kinetics law, in a recently performed investigation, but the sensitivity of the transformation to the stress state remained as an adjusting parameter. The results of the current work show that the stress state sensitivity of martensitic phase transformation in the investigated steels is microstructure-dependent and the value of this parameter is almost equal to half of the bainite volume fraction. Therefore, the volume fraction of bainite in the low-alloy multiphase TRIP800 steels can be used as a first postulation for the value of the martensitic phase transformation sensitivity to the stress state and the microstructure based model previously developed for calculating the mechanical behavior of the TRIP800 steels can be utilized as a virtual design tool for development of TRIP steels having specific mechanical properties.
M. Azadi, M. Ferdosi, H. Shahin,
Volume 17, Issue 1 (3-2020)
Abstract
In this paper, the effects of solutioning and various aging heat treatment processes on the microstructure, the hardness and electrochemical properties of a duplex stainless steel (DSS) were studied. The evaluation of the microstructure and phase compositions were carried out by the optical microscopy (OM) and the X-ray diffraction (XRD), respectively. Electrochemical behaviors of specimens were evaluated by both potentiodynamic polarization and electrochemical impedance spectra (EIS) tests at temperatures of 25 and 60 ºC. The obtained results showed that the solutioning heat treatment increased corrosion rates with respect to the blank specimen. The aging process at 490 ºC for 20 hrs increased the volume percent of the carbide phase to the highest value (25.1%) which resulted in an increase of the hardness value to 170 VHN. The specimen which was aged at 540 ºC for 10 hrs with the Cr7C3 size of 22.8 µm, exhibited the higher corrosion resistance at both temperatures of 25 and 60 ºC with respect to other aged specimens. In addition, the temperature of 60 ºC promoted the anodic reactions in 3.5 wt% NaCl solution which decreased impedance modulus values significantly. Consequently, the carbide size was more effective parameter than the carbide content in predicting electrochemical behaviors of such alloys.
S. Mortezaei, H. Arabi, H. Seyedein, A. Momeny, M. Soltanalinezhad,
Volume 17, Issue 3 (9-2020)
Abstract
Dynamic Recrystallization (DRX) is one of the likely mechanisms for fine-graining in metals and alloys. The dynamic recrystallization (DRX) phenomena occurs in different thermo-mechanical processing (TMP) conditions for various metallic materials. DRX depends on various materials and thermo-mechanical parameters such as temperature, strain rate, strain, stress and initial microstructure. in the present study, the restoration mechanism of the 17-7PH stainless steel has been investigated using a hot compression test under different conditions of thermo-mechanical treatment. The microstructural characteristics and the behavior of the hot deformation of the under study steel are investigated using flow curves and microstructure images obtained from optical microscopy. The results show that the maximum and steady state stresses are significantly affected by the strain rate and the deformation temperature. So that, the flow stress increases with decrease in the deformation temperature and increase in the strain rate. Microstructural studies confirm the occurrence of DRX as a restoration mechanism in the microstructure for the two phases of austenite and ferrite.
S. Karimzadeh, F. Mahboubi, G. Daviran,
Volume 17, Issue 4 (12-2020)
Abstract
In the present investigation effects of time and temperature on plasma nitriding behavior of DIN 1.2344 (AISI H13) steel are studied. Pulsed plasma nitriding process with a gas mixture of N2 = 25% + H2 = 75% and duty cycle of 70% is applied to cylindrical samples of DIN 1.2344 hot work tool steel. X-ray diffraction, surface roughness, microhardness and ball on disc wear test are performed and behavior of plasma nitrided samples are compared. Scanning electron microscopy and optical microscopy are used in order to observe the microstructure of samples after nitriding. XRD results showed that the compound layer is dual phase. Hardness near the surface dropped by rising the process temperature and it rose in longer process durations. The comparison of µ results showed frictional properties in longer durations with lower temperatures is approximately the same in higher temperatures with shorter durations.
Jonas Fernando Macedo, Igor Alexandre Fioravante, Roberto Zenhei Nakazato, Heloisa Andréa Acciari, Eduardo Norberto Codaro,
Volume 18, Issue 1 (3-2021)
Abstract
As we all know, corrosion of pipelines by hydrogen sulfide is the most worrying factor in the production and transport of oil and gas. In this work the corrosion behavior of API 5L X70MS and X70MO low carbon steels in hydrogen sulfide environments was investigated. Hydrogen induced cracking and sulfide stress cracking tests were carried out according to NACE TM0177 standard. After testing, blisters and cracks were observed only in X70MO steel, probably due to its lower grain refinement and banded microstructure. Internal cracks seem to be initiated in elongated MnS inclusions. Corrosion process was studied by obtaining potentiodynamic polarization curves, which were registered after open circuit potential measurements, at room temperature. Both steels showed general corrosion in NACE 177A solutions, but the corrosion rate values in H2S-saturated solution were about an order of magnitude higher than those ones in deaerated solution. Hydrogen permeation w::as char::acterized in accordance with ASTM G148 standard. In deaerated H2SO4 solution, permeation measurements were similar for both steels. In H2S-saturated solution, X70 MO exhibited higher hydrogen oxidation current values than X70 MS. H2S seems to promote the reduction of protons and increase the concentration of hydrogen atoms in the solution/steel interface, favoring the diffusion process. As X70MO has a coarse microstructure, it offers more pathways for hydrogen diffusion.
Rabah Bobaaya, Omar Allaoui, Mokhtar Djendel, Samir Benaniba,
Volume 18, Issue 3 (9-2021)
Abstract
Coatings based on chromium borides and chromium carbides are commonly employed in applications requiring mechanical performance, such as high hardness and low friction coefficient, as well as corrosion resistance. In this work, we made layers of chromium borides and chromium carbides on the surface of low carbon steel through some specific treatments. For chromium borides, the boriding treatment in a solid medium at 900 °C for 4 hours followed by chromium electroplating on the steel surface and finally the application of annealing treatment at temperatures at 950 °C for 1 and 2 hours. For chromium carbides, the cementation in a solid medium followed by electroplating of chromium on the surface and finally the application of annealing treatment at temperatures between 500 and 1100 °C for 1 hour. The obtained results show that, in the first case, boron diffusion and chromium deposition lead to chromium borides on the treated surface. Similarly, for the second case, the cemented layer and the chromium deposited on the surface combine to form chromium carbides on the treated surface after annealing. The characteristics of the chromium borides and chromium carbides obtained are very similar to those of chromium borides and chromium carbides obtained by other processes.
Mojtaba Hosseini, Ali Allahverdi, Mohammad Jaafar Soltanian Fard,
Volume 19, Issue 1 (3-2022)
Abstract
The aim of the present research work is to evaluate the feasibility of processing and utilizing steel slag
in binary and ternary cement blends with limestone. The physical and microstructural properties of binary and
ternary composite cements produced by inter-grinding mixtures of ordinary Portland cement clinker, processed
steel slag and limestone in a laboratory ball mill with replacement levels varying from 0 wt.% to 30 wt.% were
studied. The effects of processed steel slag and limestone incorporation on density of dry cement mixes and water
consistency, setting time and volume stability of fresh and hardened cement pastes were investigated. Also,
density, water absorption, total open pore volume (%) and compressive strength of cement mortars were measured.
The mix with 15 wt.% limestone and 15 wt.% processed steel slag was selected as a typical ternary cement mix
for complementary studies including X-ray diffractometry, thermal gravimetry, Fourier-transform infrared
spectroscopy, and scanning electron microscopy analyses. The results show that removal of relatively high
metallic content of steel slag increases its grindability for mechanical activation and improves its hydraulic
properties effectively and makes it suitable for being recycled in cement industry. The results show that
mechanical activation of the cement mixes enhances the poor hydraulic activity of the processed steel slag and
compensates the strength loss to some extent. The physical and chemical properties of all studied composite
cement mixes comply with ASTM standard specifications, except the compressive strength of the cement mixes
at 28-days containing 20 wt.% or higher amounts of limestone ground to the relatively low Blaine specific surface
area of about 3000 cm2/g.
Sravanthi Gudikandula, Ambuj Sharma,
Volume 19, Issue 4 (12-2022)
Abstract
The lean duplex stainless steels (LDSS) have excellent features due to the microstructural phase
combination of austenite and ferrite grains. These steels have low Ni and Mo contents which can reduce the cost
and stabilize the austenite fraction in the microstructure. In recent years, welding is used to enhance the
microstructural behaviour of LDSS. In this paper, Gas tungsten arc welding (GTAW) was performed on LDSS
S32101 with different heat energy inputs and varying welding currents. The influence of heat inputs (0.85 and 1.3
kJ/mm) on welded samples was investigated to study the microstructural behaviour, phase balance, and mechanical
& corrosion performance. The microstructures studies were carried out using an optical microscope, scanning
electron microscope and X-ray diffraction. The effect of Heat input led to the significant microstructural evolution
in weld metals with high austenite reformation. The microstructure of weldments consisted of inter-granular
austenite (IGA), grain boundary austenite (GBA) and Widmanstatten austenite (WA). Important mechanical
properties such as tensile strength and micro-hardness were investigated to understand the performance of
weldments. The polarization method was used to understand the corrosion behaviour of weldment in a 3.5% NaCl
solution. The experimental results showed enhanced properties of welds that could be suitable for industrial
applications.
Ali Ebrahimpour, Amir Mostafapour, Naeimeh Hagi,
Volume 20, Issue 1 (3-2023)
Abstract
In this research, the effect of RSW parameters including current intensity, welding time and welding force (coded by A, B and C) on the radius, thickness and area of the nugget and the radius of the HAZ of TRIP steel joints was investigated by DOE and RSM. A 3D coupled thermal-electrical-structural FEM was used to model RSW. To validate the FE model, two TRIP steel sheets were welded experimentally. During welding, the temperature was measured and the results were compared with the FE results and a good agreement was obtained. The boundaries of the welding zones were determined according to the critical temperatures and the responses in all samples were calculated. Using analysis of variance, direct, quadratic and interaction effects of parameters on the responses were studied and a mathematical model was obtained for each response. The direct linear effects of all parameters on all responses were significant. But among the interaction effects, the effect of B×C on the nugget radius, the effect of A×B on the nugget thickness, the effect of A×B on the nugget area and the effects of A×B and B×C on the HAZ radius were significant. Also, current intensity had the greatest effect on all responses.
Mohammad Abankar, Hossein Arabi, Mohammad Taghi Salehi, Majid Abbasi,
Volume 20, Issue 1 (3-2023)
Abstract
The aims of this research were to evaluate the effects of different thermomechanical treatments on the microstructure and investigate some of the mechanical properties of a TWIP steel rich in Mn & Al. So, a block of a TWIP steel with nominal composition Fe-17.5Mn-1.36Al-0.8C was cast and then subjected to hot rolling followed by cold rolling and heat treatment. Cold rolling was performed before heat treatment in order to reduce the grain size and improve the tensile and fatigue properties. X-ray diffraction technique was used before and after the heat treatment to evaluate the possibility of any phase formation. No sign of martensitic transformation after cold deformation was observed. However, by increasing the amount of cold deformation, the number of mechanical twins and slip band increased resulted to an increase in hardness and strength. The best tensile and fatigue result were obtained after 47% thickness reduction and annealing at 715˚C for 10 min. Under these conditions, the mean grain size reduced from 138 to 9 μm resulted to an increase in yield strength from 395 to 510 MPa, and the fatigue life improvement from the mean life of 10200 for the cast sample to 21500 cycles for the treated sample, when these samples underwent fatigue tests at a stress range of 650 MPa and R=0. In addition, the diameter and depth of dimples in fracture surfaces decreased by reducing the grain size but the fracture mode was remained ductile and adequate plastic deformation occurred before failure.
Mohammad Javad Sohrabi, Hamed Mirzadeh, Saeed Sadeghpour, Reza Mahmudi,
Volume 20, Issue 4 (12-2023)
Abstract
Deformation-induced α΄-martensite generally forms at shear bands in the coarse-grained austenite, while it nucleates at grain boundaries in the ultrafine-grained (UFG) austenite. The available kinetics models are related to the nucleation on the shear band intersections, and hence, their application to investigating the kinetics of α΄-martensite formation for the UFG regime cannot be justified. Accordingly, in the present work, the general Johnson–Mehl–Avrami–Kolmogorov (JMAK-type) model was implemented for comparing the kinetics of α΄-martensite formation in the UFG and coarse-grained regimes using an AISI 304L stainless steel. On the experimental front, the X-ray diffraction (XRD) patterns and the electron backscattered diffraction (EBSD) maps were used for phase and microstructural analyses, respectively. It was revealed that the simple JMAK-type model, by considering the dependency of the volume fraction of α΄-martensite on the strain, is useful for modeling the experimental data, predicting the nucleation sites based on the theoretical Avrami exponents, and characterizing the transformation kinetics at low and high strains.
