Sciences des matériaux

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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

damage analysis of composite materials

FACI Youcef 1, A.Mebtouche2, B.Berdjene B.Maalem, H.DEHDOUH  (2019)
Article de conférence

Fiber reinforced composite materials have been increasingly used as structural material in airplanes and in space applications because of their high specific stiffness and strength. This work presents the results of the damage kinetic of carbon fiber reinforced polymer using the acoustic emission under solicitations. The correlations between acoustic emission parameters and damage mechanism are identified, and then confirmed by microscopic observations. This review will emphasize the roles that AE can play as a tool for the composite materials, damage mechanisms, and characterization of damage evolution with increasing time or stress, the localization and origin of damage, quantification of crack size based on energy release from concrete structures in the field and reduction in the numbers of test specimens required in various studies. Voir les détails

Mots clés : kinetic, damage, simulation, energy, acoustic emission.

Preparation, structural and functional properties of PbTiO3-δ ceramics

Khiat Abd elmadjid, Felicia Gheorghiu, Mokhtar Zerdali, Mohammed Kadri, Saad Hamzaoui  (2019)
Publication

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

Effect of zinc/cadmium proportion in CdS layers deposited by CBD method

R. Zellagui, H. Dehdouh, F. Boufelgha, A. Boughelout, T. Sahraoui, D. Chaumont, M. Adnane  (2019)
Publication

Cadmium poisoning and the cost of panel recovery which is very expensive and difficult in the buffer layers of CdS in solar cell, for these two drawbacks, we do a search on the effect of proportion of zinc/cadmium in the properties layers of CdS. For this, our studies study the properties of CdxZn1-xS layers deposited by chemical bath (CBD). CdZnS thin films were synthesized by chemical bath deposition (CBD) with different deposition protocols to optimize deposition parameters such as temperature, deposition time, ion concentrations and pH. The surface morphology, structural, optical and chemical properties of the CdZnS thin films were studied by SEM, XRD, Raman and UV-visible spectrophotometer. The transmittance is 80% in the visible region 300 nm - 800 nm; the crystalline structure is hexagonal and cubic, the grain size is between 9.95 to 25.82 nm. It is observed that the transmittance and the shape change with the concentration of zinc in the solution; this result favors the application of these films in solar cells application. Voir les détails

Mots clés : CdZnS, chemical bath, SEM, Raman, solar cells, Thin films

Effet du niobium sur la résistance à l’usured’une fonte au chrome traitée thermiquement

K. BOUHAMLA, A. HADJI, H. MAOUCHE, H. MERRADI  (2011)
Publication

Chromium cast irons are well known for their wear properties. They are widelyused in engineering practices such as mining, cement industries and many others. Theirwear properties are mainly due to their microstructure which is constituted by netted M7C3type eutectic carbide held in an austenitic or martensitic matrix. Several researchers investigatedthe possibility of improving the wear properties of these cast irons by acting onthe microstructure, the morphology of the microstructural constituents as well as on theirdistribution. The present work consists in studying the effect of the niobium on the wearbehaviour of a heat treated chromium cast iron. Characterizations by optical microscopy,abrasion and friction tests are realized in order to establish the wear resistance of this castiron and also the type of microstructure having been at the origin of this improvement. Theobtained results show that the studied material is a 15% chromium white cast iron. Niobiumaddition had an effect on the microstructure as well as on the abrasion and frictionresistances of the heat treated high chromium white cast iron samples. The wear resistanceincreases with the increase of the niobium content. Voir les détails

Mots clés : Chromium cast iron, wear, eutectic carbides, alloying elements

Etude de l’influence de la composition chimique sur laformation de la structure et la tenue à l’usure des fontes auchrome

BOUHAMLA Khedidja (2015)
Thèse de doctorat

The use properties modification of chromium cast iron can be insured by severalmethods as chemical composition variation, carbide former alloying, by heat treatment and bymechanical processing. Alloying elements have been used in many research works usinghypoeutectic, eutectic, hypereutectic compositions of weakly and high alloyed chromium castirons. The target is to obtain a cast iron with respect of services requirementsCement, mining and steel making industries, in their daily practices of grinding andcrushing, require parts having high wear resistance. These operations take place in a veryaggressive environment because the grinding and the crushing of raw materials take placeunder the influence of the requests of abrasion and of the friction.The object of the present work is aimed on « Study of the chemical compositioninfluence on the structure formation the wear behavior of a chromium cast iron". The usedmethodology consisted of forming element addition. It is about manganese, niobium,vanadium, molybdenum and titanium. At first the manganese was only added to the melt thencombined with one, two and three elements. The chemical analysis, optical and SEMmicroscopy was used to characterize the microstructure of the studied compositions. TheDRX was much more used to define the type and the proportion of the formed phases as wellas the effect brought by the carbide former addition the crystalline parameters of the formedphases. The DSC technique gave thermal behavior of studied compositions, the wear testsdefined the wear behavior and shown the effect of the addition of alloying elements Voir les détails

Mots clés : fonte au chrome, microstructure, usure, Eléments d'addition

EFFECT OF HEAT TREATMENT ON WEAR BEHAVIOUR OF FORGEDSTEEL BALLS

K. BOUHAMLA, H. MAOUCHE, A. KETTACHE, S. TLILI, S.E. BOUTEBBA  (2018)
Article de conférence

The raw material preparation sector such as cementworks, the steel and mining sector is beginning to pay attention toforged balls as an alternative to the cast balls for their best usecharacteristics. The forging materials are stronger than thecasting material because of their fiber structure. The forgingtechnique, in contrast to the casting process, contributes to asignificant improvement of ball wear behavior during thegrinding process.The wear behavior depends on several factors including thechemical composition of the alloy, the type of microstructure andthe applied heat treatment. In this work we focus on the effect ofaustenitizing temperature on the type of the producedmicrostructure. Al the heat treatment parameters were fixed forall the samples except the austenitizing temperature. Threeaustenitizing temperatures are selected and a tempering at 250°C with a holding time of one hour followed by cooling has beencarried out. The study is carried out on medium micro-alloyedcarbon steel intended for heat treatment.To make clear the effect of the temperature on themicrostructural transformation, several investigations wereachieved. Optical and SEM microscopy was carried out toqualitatively characterize the phases A microstructural analysisusing the Rietveld method was conducted to access, for eachtemperature, the type and proportion of phases as well as thecrystallites size. Voir les détails

Mots clés : grinding balls, forging, heat treatment, characterization, XRD analysis, Rietveld refinement

Effect of heat treatment temperature on thestructural evolution of hot forged steel balls used forgrinding raw material in cement industry

K. BOUHAMLA, M. BOUREBIA, M. CHAOUR, A. GHARBI, H. MAOUCHE  (2018)
Article de conférence

The raw material preparation sector such as cementworks, the steel and mining sector is beginning to pay attention toforged balls as an alternative to the cast balls for their best usecharacteristics. The forging materials are stronger than thecasting material because of their fiber structure. The forgingtechnique, in contrast to the casting process, contributes to asignificant improvement of ball wear behavior during thegrinding process.The wear behavior depends on several factors including thechemical composition of the alloy, the type of microstructure andthe applied heat treatment. In this work we focus on the effect ofaustenitizing temperature on the type of the producedmicrostructure. Al the heat treatment parameters were fixed forall the samples except the austenitizing temperature. Threeaustenitizing temperatures are selected and a tempering at 250°C with a holding time of one hour followed by cooling has beencarried out. The study is carried out on medium micro-alloyedcarbon steel intended for heat treatment.To make clear the effect of the temperature on themicrostructural transformation, several investigations wereachieved. Optical and SEM microscopy was carried out toqualitatively characterize the phases A microstructural analysisusing the Rietveld method was conducted to access, for eachtemperature, the type and proportion of phases as well as thecrystallites size. Voir les détails

Mots clés : grinding balls, forging, heat treatment, characterization, XRD analysis, Rietveld refinement

Approche expérimentale des causes d’endommagement des marteaux de concassage

K. BOUHAMLA, S. Boudebane, A. SAKER, M. BOUREBIA, A. GHARBI  (2018)
Article de conférence

Les matériaux résistant à l’usure sont fortement demandés par divers secteurs industriels (industries minières, métallurgiques et autres). Ils constituent des pièces maîtresses des concasseurs et des broyeurs utilisés pour la préparation des matières. Plusieurs nuances d’aciers sont produites pour répondre aux besoins de divers secteurs industriels. D’autres aciers martensitiques à haute teneur en carbone et en chrome sont aussi produits pour répondre à des sollicitations nécessitant une résistance à l’usure élevée.Dans ce travail nous nous intéressons aux causes de dégradation prématurée des marteaux de concassage. Ces marteaux, à leur entrée en service, cassent au niveau de la bride de fixation en libérant la majeure partie de la pièce dans le concasseur. Le matériau étudié est un acier à haute teneur en chrome. Plusieurs techniques ont été employées pour caractériser ce matériau et détecter les causes qui sont à l’origine de ce problème. Les échantillons ont été analysés par spectrométrie X. La microscopie a contribué à la révélation de la microstructure et aussi à faire ressortir les éventuels défauts micro et macroscopiques existants. La diffraction des rayons X a aidé à détecter le type et la proportion des phases microstructurales. Voir les détails

Mots clés : Acier moulé, endommagement, marteau de concassage, usure, microstructure, défauts