Sciences des matériaux

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Natural extract of Opuntia ficus indica as green inhibitor for corrosion ofXC52 steel in 1M H3PO4

Amel Oulabbas, Abd errahmane Sihem (2019)
Article de journal

The purpose of this study is to evaluate the anti-corrosive effect of natural extract of Opuntia Ficus Indica (O.F.I) for XC52steel in 1M H3PO4. Experimental work has been achieved by weight loss, potentiodynamic polarization and EISmeasurement, as well as SEM surface characterization. Among the results obtained, we can mention an inhibitory efficiencyof 90% by gravimetric method and 83.9% by electrochemical method at 10% (v/v) of O.F.I. Moreover, The O.F.I extract actsas a mixed inhibitor; however, adsorption free enthalpy indicates a physisorption. The adsorption obeys the Langmuirisotherm model. These results have been improved by SEM micrographsVoir les détails

Mots clés : corrosion, Opuntia ficus indica, EIS, green inhibitor, XC52 steel

Effect of welding heat input on microstructure and residual stresses of duplex stainless steel weldments

N. OUALI, K. Khenfer, B. BELKESSA, B. Cheniti (2019)
Article de conférence

In the present investigation, the influence of heat input on microstructure, residual stresses and corrosion resistance of lean duplex stainless steel welds are discussed. The weldments were made with different heat inputs through changes in welding current and travel speed, using tungsten inert gas process. The microstructural evolution was characterized using optical and scanning electron microscopy, while the residual stresses were measured on surface and thickness by X-ray diffraction technique. The experimental results show significant changes in microstructure and ferrite content with a large fraction of reformed austenite. Samples exhibit compressive residual stresses on the weld surface. Potentiodynamic polarization tests evaluated in 3.5% NaCl solution exhibit high corrosion resistance of the weld metal produced with the low heat input.Voir les détails

Mots clés : Lean duplex stainless steel, Welding TIG process, heat input, residual stresses, X-ray diffraction 1. Introduction:

Effect of filler metal on mechanical properties and corrosion behavior of dissimilar metals welds

B. BELKESSA, D. Miroud, B. Cheniti, N. OUALI (2019)
Article de conférence

This work purposes to investigate the microstructure and the mechanical behavior of dissimilar metals weld between 2205 duplex stainless steel (UNS 31803) and high strength low alloy steel API X52. The joining was produced by shielded metal arc welding process using two different filler metals, the duplex E2209 and austenitic E309 grade.The microstructures of the dissimilar welded joints have been investigated by optical microscopy, scanning electron microscopy and energy-dispersive spectroscopy (EDS). The EDS analysis performed at the API X52/weld metal interface showed an evident gradient of Cr and Ni between fusion and type II boundaries, where the highest Nano hardness value was recorded.Voir les détails

Mots clés : Dissimilar metals welding; 2205 duplex stainless steel; API X52 HSLA steel; Heat-affected zone.

Two dimensional heat transfer numerical model for secondary cooling in continuous casting process

H. Tayoub, H. Bendjama, K. Hamlaoui, K. SLIMANI, S. AOUABDI (2019)
Article de conférence

The continuous casting process is responsible by most of the steel manufacturing in the entire world while maximizing production output. Although the continuous casting of steel began almost 60 years ago, its production still suffers from several serious defects in the final product. Since the process is essentially a process of heat transfer between the metal and different cooling zones, the quality of slabs in the continuous casting can be strongly influenced by the temperature variation through the process of solidification. Therefore, the objective of the present work is to determine a 2D numerical model of solidification and heat transfer along different cooling zones of a secondary cooling during continuous casting process. Numerical model has been created and the obtained numerical results from the present model show that the optimal control of the cooling parameters in secondary cooling is inevitable in order to obtain high-quality final product and casting productivity. Numerical results were validated and the comparison shows that there is a good agreement with experimental measurements.Voir les détails

Mots clés : Continuous casting of steel, secondary cooling, Heat transfer, Defect, solidification

Effect of microstructure and precipitation phenomena on theMechanical behaviour of AA6061-T6 aluminum alloy weld.

M.HAKEM, S. Lebaili, S. Mathieu, D. Miroud, A. LEBAILI, B. Cheniti (2019)
Article de conférence

In the present study, the effect of microstructure and precipitation phenomenaon the micro hardness of Tungsten Inert Gas (TIG) welded AA6061-T6 aluminum alloyare investigated. The microstructure features showed mainly the grains of aluminum solid solution with the presence of some precipitates at the grain boundaries. Scanning electron microscope micrographs exhibited the presence of Fe-based intermetallic and B-equilibrium precipitates throughout a-Al grains. In the heat-affected zone (HAZ), the dissolution, over-aged and coalescence of precipitates are observed; their hardening effects disappear and a decrease in strength and hardness are noticed.Voir les détails

Mots clés : Aluminum alloys, TIG welding, precipitates, microstructure

Study of Inhibitory Efficacy of Natural Extract of Opuntia Ficus Indica as Green Inhibitor for Corrosion of Mild Steel in Drilling Water

OULABBAS Amel, Achouri Sihem1, Meddah Soumaya1, Remichi Nasser1, Ramoul Chems Eddine1, TLILI Samira (2019)
Article de conférence

The purpose of this study is to evaluate the anti-corrosive effect of natural extract of Opuntia Ficus Indica (O.F.I) for X60 mild steel in drilling water environment used in petroleum engineering. Experimental work has been achieved by weight loss, potentiodynamic polarization and EIS measurement, as well as SEM surface characterization. Among the results obtained, we can mention an inhibitory efficientcy of 90% by gravimetric method and 80% by electrochemical method at 20% (v/v) of O.F.I.  Moreover, The O.F.I extract acts as a mixed inhibitor; however, adsorption free enthalpy indicates a physisorption. The adsorption obeys the Langmuir isotherm model.Voir les détails

Mots clés : corrosion, Mild steel, green inhibitor, Opuntia Ficus Indica and Electrochemical Impedance spectroscopy

The corrosion resistance ofsupermartensitic steels compared to martensitic steels in different corrosion media

A.Oulabbas S. Tlili, C.E. RAMOUL, S. Meddah, F. Sehab (2017)
Article de conférence

The supermartensitic stainless steels deduced from the refinement of the compositionof martensitic steels, have a low carbon content with 13% of chromium, 5% of nickel and 2%of molybdenum, this new generation of steel has an improved ductility with a good resistancemechanical and excellent resistance to corrosion. In this work, a comparative study of thecorrosion behavior of these two stainless steels in different aggressive chlorinated andsulphurized media was carried out. Stationary (polarization curves) and transient(electrochemical impedance) electrochemical methods have been applied. The rate ofcorrosion as a function of time was determined by the mass loss method and thecharacterization of the surface condition was studied by optical microscopy. Two types ofcorrosion were observed: uniform corrosion in which the half-reactions are homogeneouslydistributed in 0.5M H2SO4, followed by localized corrosion observed in 0.5M NaCl for bothsteels. According to the polarization curves, the corrosion potential differs betweenmartensitic steel and supermartensitic steel where it has a higher potential with -0.342 V / Ag/ AgCl in 0.5M H2SO4 and -0.339 V / Ag / AgCl in 0.5M NaCl. In parallel, the polarizationresistance given by EIS shows that in both media, supermartensitic steel is more resistant thanmartensitic steel where it has an Rp equal to 7200 Ohm in 0.5M H2SO4 and 8340 Ohm 0.5MNaCl. These results are confirmed by the optical microscope microstructure.Voir les détails

Mots clés : corrosion, martensitique stainless steel, supermartensitique stainless steel

L’Etude du comportement à la corrosiondes aciers inoxydables supermartensitiques et martensitiques dans deux milieux corrosifs

A. Oulabbas, S.Tlili, C.E. RAMOUL, S.Meddah (2018)
Article de conférence

l'objectif de notre travail est d'étudier la résistance que les aciers inoxydable martensitique et supermartensitique présentent lors d'une attaque à la corrosion chimique. pour cela deux milieux d'attaque le premier chloruré et le second sulfaté, sont utilisés comme électrolytes. la premiere approche éttant la technique de perte de masse suivit par l'étude du comportement électrochimique ( courbe de polarisation et impédance) d'aprés les courbes de polarisations , le potentiel de corrosion différe entre l'acier martensitique et supermartensitique, ou ce dernier présente un potentiel plus noble et cela dans les deux milieux. Voir les détails

Mots clés : acier martensitique, acier supermartensitique, impédance, corrosion

CONTRIBUTION TO CHARACTERIZATION OF NATURAL DIATOMITE

Hazem MERADI, kotbia LABIOD, Wafia GHABECHE (2019)
Article de conférence

With the complex examination of raw material from a Sig deposit in Algeria in the region of Mascara area, physical, chemical and mineralogical properties of diatomite have been defined. It has been found that it is a dominantly amorphous material, sedimentary rock of the type silica-diatomite. The raw material consists of approximately 60% SiO2. Of the physical properties, more significant is porosity, which is higher than 60%. The raw material has a wide spectrum of possibilities for practical application: intensive absorbent for several types of liquids and chemical properties of the soil, natural insecticide, and filter water etc. For determination of the chemical contents, properties and origin of the raw material the following methods have been used, such as, chemical analysis, XRD analysis, optical microscopy and thermal analysis.Voir les détails

Mots clés : diatomite, X-ray, XRD, Sig.

Preparation, structural and functional properties of PbTiO3-δ ceramics

Khiat Abd elmadjid, Felicia Gheorghiu, Mokhtar Zerdali, Mohammed Kadri, Saad Hamzaoui (2019)
Article de journal

In the present study, oxygen deficient PbTiO3-δ ceramics were prepared by solid state-reaction method. The formation of the pure perovskite phase with tetragonal structure was confirmed for the 800 °C/2 h calcined sample by using X-ray diffraction analysis at room temperature. Energy dispersive X-ray spectroscopy analyses confirm the creation of oxygen vacancies in the system for charge compensations, as demonstrated by the percentage of O atoms of ∼53%. The complex impedance data reveals important contributions of the oxygen vacancies to the total dielectric response that are homogeneous distributed within the sample. The room temperature magnetic properties show a weak ferromagnetic character in all the samples that might be attributed to the oxygen vacancies defects and to surface effects.Voir les détails

Mots clés : Ceramics, oxygen vacancies, EDX spectra, Dielectric properties, Magnetic Properties