Métallurgie

Nombre total de résultats : 175
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Effets des éléments (vanadium et niobium) sur la structure et le comportement à la corrosion de l’acier inoxydable austénitique de type AISI309

Gharbi amel (2019)
Thèse de doctorat

Les aciers inoxydables austénitiques sont utilisés dans des environnements agressifs couvrant de larges domaines tels que le secteur alimentaire, chimique et nucléaire. Par ailleurs, ils doivent présenter des propriétés d’emploi adéquates et une durée de vie optimale. Ainsi, plusieurs méthodes sont employées afin d’améliorer ces propriétés à savoir l’addition des éléments chimiques, le traitement thermique et le traitement de surface. Cette étude porte sur l'influence de l'addition du vanadium et du niobium sur la variation de la microstructure, l’évolution des propriétés mécaniques et le comportement électrochimique d’un acier inoxydable austénitique de type AISI309.  Un traitement de mise en solution a été appliqué sur l’acier inoxydable de base et l’acier inoxydable allié au vanadium et au niobium à une température de 1100°C pendant trois heures suivi d’un refroidissement rapide à l’eau. Ce traitement a été suivi d’un revenu à différentes températures suivi d'un refroidissement à l’air. La caractérisation microstructurale a été effectuée par microscopie optique, MEB, EDS, DRX, DSC. Afin, d’évaluer la résistance à l’usure des matériaux étudiés, une caractérisation mécanique des échantillons étudiés a été réalisée au moyen des mesures de dureté et des essais d’usure par frottement. De plus, pour examiner le comportement à la corrosion, des tests potentiodynamiques et des mesures d’impédances électrochimiques (EIS) ont été réalisés dans deux milieux HCl et H2SO4.  L'inhibition à la corrosion de l'acier inoxydable austénitique de type AISI309 avec et sans ajout de vanadium et de niobium par 2,2’-Bipyridyl dans H2SO4 a été étudiée en utilisant la polarisation potentiodynamique (Tafel), la polarisation linéaire (LRP) et la spectroscopie d'impédance électrochimique (SIE). D’après les résultats expérimentaux il a été constaté la présence d’une précipitation des carbures de niobium et de vanadium de type MC (VC, NbC) au détriment d’une précipitation intergranulaire de carbures riches en chrome, ainsi qu’une amélioration des propriétés mécaniques tels que la résistance à l’usure et la dureté suite à l’ajout des éléments d’alliage (vanadium et du niobium) avec et sans traitements thermiques. Par conséquent, l’addition du vanadium et du niobium a contribué à l’amélioration du comportement à la corrosion dans les milieux envisagés ainsi que l’efficacité inhibitrice de l’acier étudié en présence d’inhibiteur (2,2’-Bipyridyl). Voir les détails

Mots clés : AISI309, Cr23C6, Vanadium, niobium, 2, 2'-bipyridyle, corrosion, microstructure, propriétés mécaniques, comportement électrochimique, dureté, usure par frottement

Contribution à la diminution des criques de rives qui apparaissent dans les bramesd’acier en coulée continue.

HAMLAOUI Katib (2016)
Mémoire de magister

En coulée continue, la qualité des produits et la productivité de l'installation sontfortement dépendantes du réglage du refroidissement secondaire adopté.Le problème de recherche concerne l’ACO1 (aciérie à oxygène numéro1) localiséeà Arcelor-Mittal/Annaba. Il concerne les brames présentant des défauts de criques derives.La rupture à chaud, ou crique à chaud est un défaut majeur en solidification, quiconduit au rebut de nombreuses pièces dans différents procédés industriels tels que lasolidification en lingotière, la coulée continue de brames.Les défauts les plus répandus au niveau de la coulée continue (Arcelor-Mittal -Annaba) sont les criques de rives : Elles sont petites et fines, sur les coins, longueurenviron 50 mm, profondeur 1 à 2 mm. Elles sont à cheval sur la face et sur la rive.L’élaboration d’un modèle thermomécanique permettant de prédire les profils detempérature sur les différentes faces de la brame en fonction de son passage d’unezone de refroidissement à une autre de la machine de coulée continue et notammentsur les bords.Cette étude confirme la nécessité de considérer les défauts de criques de rives vis-àvisde leur présence au niveau des brames lesquelles sont laminées à chaud ; leproduit final étant une bobine qui doit être saine. Voir les détails

Mots clés : coulée continue, acier, brames, criques de rives

Thermal Treatment Effect on Tribological and Corrosion Performances of 13Cr5Ni2Mo Super- Martensitic Stainless Steel

S. TLILI, N.E. BELIARDOUH, C.E. RAMOUL, O . I . A bdullah, H . K aleli, M . A . S amad  (2018)
Publication

Wear behavior of 13Cr5Ni2Mo supermartensitic stainless steel (SMSS) were investigated in air and in argillaceous paste at room temperature. Prior to wear testing, the samples were subjected to two treatments, namely; quenching followed by double tempering. A pin-on- disc test rig was used to conduct the wear test with a tribo-pair consisting of supermartensitic stainless steel sliding against itself. It was observed that the microstructure of the thermally treated samples mainly consisted of tempered martensite and carbides. Wear results showed that oxidative and abrasive wear dominated the wear process of the treated samples in both dry conditions and in argillaceous paste. Additionally corrosion tests were performed in 5.0% NaCl solution via potentiodynamic polarization tests. It was found that the passive film formation provides a good corrosion resistance to the samples. Voir les détails

Mots clés : Martensitic Stainless Steel, Thermal Treatments, wear, corrosion

Frittage et nitruration liquide des comprimés de l’alliage Fe-Ni-Mo-Al-Ti

MEDDAH Soumaya (2008)
Mémoire de magister

One of the disadvantages of sintered materials obtained by solid phase sintering is the open residual porosity which limits the application of certain treatments such as thermochemical treatments in a liquid medium. Therefore, nitriding is not recommended for sintered materials because of risks of infiltration of the saturating liquid medium in the open porosity generating in the long term internal corrosion of the structure.Our study presents the results of the nitriding of sintered Fe-20% Ni-1% Mo-X% Al-Y% Ti alloy tablets (where X and Y vary from 1 to 6 and 1 to 4 respectively). . During sintering, these compositions cause the formation of an aluminum-based liquid phase which favors the partial elimination of the open porosity. Our interest was in the first place, in the study of the influence of aluminum additions on the character of diffusion, as well as on the evolution of porosity and on the formation of the structure of the sinter, and second, on the repercussions of nitriding on this new structure.The results of the micrographic analysis revealed a clear evolution of the character of the porosity, with a tendency to the elimination of open pores. Structurally, sintering has resulted in an array of intermetallics as a result of the interaction of liquid aluminum with other solid particles. The microhardness profiles showed that despite the selective nature of the diffusion of nitrogen and carbon during cyanidation, the saturation was at heart, with the formation of islands of AlN, TiC (C, N) . As for the properties, the appearance of Fe-Al, Ni-Al and Ti-Al intermetallics during sintering gave the material good resistance to hot oxidation. Cyanidation modifies the oxidation behavior of the material and significantly improves its hardness. Voir les détails

Mots clés : composite, Sintering, Porosity, liquid nitriding, Oxidation

Tribological behaviour of a continuous hot dip galvanized steel

A.Taleb, M. Labaiz, A. Iost, A. Montagne, A. Ourdjini, A. Grairia, S. Meddah  (2018)
Publication

The aim of this work is to investigate the tribological behaviour of a continuous hot dip galvanizedsteel. This paper presents a fundamental study of the characteristics of zinc coating in terms ofmorphology, surface roughness and tribological behavior according to process parameters typical ofindustrial processes continuous galvanization. The morphology of the zinc coating was observed byscanning electron microscope (SEM), optical microscopy, and the mechanical properties of thecoating layers were determined by nanoindentation. The tribological tests were carried out on arotating ball-disk tribometer under loads of 1, 2, 3Nwith a sliding distance of 15, 30 and 50 m. Theresults showed a marked increase of the coefficient of friction with increasing applied load. Under thesame conditions, wear slightly increased due to the hardness of intermetallic phases. The resultspresented show that heating promotes the diffusion of iron in the zinc coating giving shape to a binaryalloy Fe–Zn whose characteristics depend on the parameters; moreover, it is proved that thetribological characteristics of the surface of the metal blank in terms of coefficient of friction dependon the temperature of the contact pressure. Voir les détails

Mots clés : galvanized steel, wear, roughness, Nanoindentation, intermetallic phases

Tribological and Eelectrochemical Characterization of a Titanium Alloy in a Physiological Solution.

S. Meddah, H. Chadli, S. TLILI, C. Ramoul, S. Challi, F. Sehab, A. Oulabbas  (2017)
Article de conférence

Titanium alloys are used primarily for biomedical and / or dental applications. They are characterized by a better mechanical compatibility with the tissues and a good biocompatibility in the body fluids. The alloy TA6V4 used in orthodontics is subject to degradation by wear and corrosion. In this context, we are primarily interested in the study of the dry friction wear of the TA6V4 / Al2O3 torque by means of a rotating Ball / Disc tribometer. In order to evaluate the biocompatibility of this alloy, an electrochemical study in a physiological solution was carried out using conventional electrochemical measurement methods (time-dependent monitoring of the corrosion potential, potentiodynamic curve) as well as Electrochemical impedance spectroscopy. The results of tribology, the friction of the torque TA6V4 / Al2O3 against each other, revealed a friction coefficient of 0.2 and a wear volume of the order of 22.579.10-12 mm3/N.mm. The wear mechanism studied by scanning electron microscopy revealed abrasive and adhesive degradation. From the electrochemical point of view, the TA6V4 alloy in Hank's solution exhibited good corrosion resistance with a polarization resistance of 44 540 Ω. Analysis by electrochemical impedance spectroscopy indicated that this alloy is passive in nature, following the formation of a surface-stable two-phase oxide layer composed of an internal compact layer which has good corrosion resistance And an external porous layer which is favorable to osteointegration. Voir les détails

Mots clés : Alloy TA6V4, Corrosion behavior, friction

ETUDE DES PROPRIETES MECANIQUES DES VERRESOXYGENES ET OXYHALOGENES

BACHIRI Abdalkader (2012)
Mémoire de magister

The rapid development of photonics technology requires increasingly efficient materials,suitable for photonic devices such as amplifiers and materials for high power lasers. Theoptical amplification based on the principle of the laser effect can be obtained in crystalline orglassy matrix through radiative emission of rare earth ions.The glasses are among the interesting matrices for transparency in a wide optical region andtheir ability to receive large amounts of rare earth ions. For this purpose, a new family ofglasses stable oxide and halide in the ternary systems Sb2O3-PbCl2-As2O3 and Sb2O3-PbCl2-AgCl has been developed. Several characterizations were made on two ternary systems. Allproperties changes almost linearly with the variation of the composition. The results obtainedare similar to those of other work. It appears that the structure of these glasses is more openwhere the low values of mechanical properties. Because of these glasses good candidates innonlinear optics. Differential scanning calorimetry has shown that certain compositions do notexhibit crystallization peaks where their high thermal stability.In this work, we also find the study of the devitrification of glasses in the ternary systemoxyhalogenated Sb2O3-PbCl2-AgCl has been studied by differential scanning calorimetry.A single exothermic peak of recrystallization is observed beyond the glass transitiontemperature, which allows the application of relations Mehl-Avrami-Kolmogorov-Johnson.The use of non-isothermal procedures for determining the values of the Avrami exponent nand activation energy E.The mechanism of crystal decay is discussed in relation to the observations in scanningelectron microscopy Voir les détails

Mots clés : transparency, ternary systems, glasses, Differential scanning calorimetry, Thermal stability

Contribution à la modélisation du processus de refroidissement secondaire d’acier coulée en continue

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

Dans l’industrie sidérurgique, la coulée continue est le procédé qui se situe entre l’élaboration d’acier et le laminage. Ce procédé a pris, depuis 30 ans, une place de plus en plus importante dans la filière de production en raison des avantages par rapport à la technique traditionnelle de coulée en lingots ; économie d’énergie et de main d’œuvre, meilleur rendement et amélioration de la qualité du produit, ainsi l’amélioration du rendement métallique de la coulée et la possibilité de couler des produits de plus faible section, directement adaptés aux laminoirs finisseurs. La coulée continue permet de transformer le métal liquide en métal solide en des formes simples, et de façon continue. Un des soucis majeurs dans l’industrie de l’acier est l’amélioration de la qualité finale du produit. Certes, le produit final présente parfois des défauts, qui sont difficiles à détecter pendant la fabrication ; la plupart du temps, ils ne sont détectés que dans les phases finales de fabrication. L’objectif de ce travail consiste à fournir un modèle numérique du refroidissement secondaire permettant de prédire l’évolution du débit de refroidissement secondaire en fonction de la vitesse de coulée dans chaque zone des nuances de l’acier. Voir les détails

Mots clés : Modélisation thermomécanique, coulée continue, refroidissement secondaire, acier, Défaut.

ETUDE ÉLECTROCHIMIQUE COMPARATIVE D’UN ALLIAGE (TiNi) ÉLABORÉ, AVEC UN IMPLANT DENTAIRE EN MILIEU SIMULÉ

Soumaya MEDDAH (2018)
Thèse de doctorat

Good mechanical compatibility with cellular tissue and corrosion resistance, as well as excellent biocompatibility in body fluids, are required for titanium-based alloys to be materials of choice for biomedical applications such as orthopedic implants and dental. The present thesis aims to obtain TiNi binary alloys developed by vacuum induction, as a possible alternative for dental applications. The TiNi alloys developed as part of this thesis work contain Ni contents ranging from 40 to 60%. The choice of this composition was made, first to check the influence of the Ni content on the formation of the structure and the morphology of the phases and secondly the repercussions of this structure on the final properties of the alloy to know; the mechanical properties, tribological and electrochemical and bioactivity. TA6V4 alloy is used for comparison.For this purpose, the chemical composition of the TiNi alloys and the microstructural evolution was determined by scanning electron microscopy (SEM) coupled to the EDS. The formation and growth of the phases was followed by X-ray diffraction. Instrumented hardness measurements were made to assess the hardness and Young's modulus of the alloys. The coefficient of friction of the TiNi alloys and the wear rate were determined by dry sliding at different loads. The electrochemical characterization in Hank's solution and artificial saliva has been studied by stationary techniques and by EIS at different immersion times. The tribocorrosion behavior was performed in artificial saliva to understand the tribocorrosion mechanisms of TiNi and TA6V4 alloys. The bioactivity tests were performed in the SBF solution after 21 days of immersion. The SEM / EDS and RX results show that the two alloys Ti50Ni50 and Ti40Ni60 have a TiNi type matrix (NiTi), and Ti2Ni and Ni2Ti type precipitated phases. The revealed microstructure for the Ti60Ni40 alloy is a Ti2Ni-based matrix comprising the NiTi intermetallic. This same alloy had the lowest Young's modulus, while the Ti40Ni60 alloy had superior superelasticity, than the other titanium alloys (Ti50Ni50, Ti60Ni40 and TA6V4).All TiNi alloys exhibit better tribological behavior compared to the TA6V4 alloy which results in high wear resistance and low wear. Abrasive and adhesive wear mechanisms have been identified as degradation mechanisms for TiNi and TA6V4 alloys, with the predominant adhesive mechanism for TiNi alloys. The Nyquist and Bode impedance diagrams for all TiNi and TA6V4 alloys show capacitive loops with two time constants, indicating that the passive film is formed of two layers namely, a compact passive internal barrier layer and a porous outer layer. The electrochemical study revealed that all alloys have a passive character. The corrosion resistance of the TA6V4 alloy is greater than that exhibited by the various TiNi alloys. TiNi alloys showed hydroxyapatite formation under in vitro bioactivity conditions of SBF. Voir les détails

Mots clés : Titanium alloys, Young module, superelasticity, wear behavior, corrosion resistance, impedance, bioactivity.

Simulation and Modeling of Uncertainties in the Calibration of a Fluorescence Chemical Spectrometer (FRX)

S. Djemili, A. HAMOUDA, D. BERDJANE, B. Maalem  (2018)
Article de conférence

Sensitivity analysis and uncertainty estimation are of major importance for the declaration of conformity of finished products. Models must be sought to analyze the test data. The main objective of this work is to establish reliable models to analyze our experimental data and validate them. So we have studied and used the Monte Carlo and Bootstrap simulation methods, we have been able to realize programs that calculate the uncertainty according to the ISO 8466 standard on X-ray fluorescence spectrometer samples from the URASM CRTI chemical analysis laboratory. Programs and interfaces are made with Matlab (GUI). Voir les détails

Mots clés : Simulation; uncertainties; Monte carlo; Bootstrap; calibration