Sciences des matériaux

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Effect of Heat Treatment on Tribological Behavior of Forged Steel Balls

BOUHAMLA Khedidja, Bourebia Mounira, Gharbi amel, MAOUCHE Hichem, CHAOUR Mohamed, Belhadi Salim (2019)
Article de conférence

The grinding balls work under severe wear conditions. Different stresses taking place during the grinding operation may cause material wear whose rate differs from material type or manufacturing process. As a result, these numerous stresses can alter the life cycle of the material. In the grinding field, there are grinding bodies made of chromium cast iron and forged steel. In several aspects, chromium cast iron balls differ widely from the forged steel balls. Heat treatment is a recommended solution to improve the wear behavior of grinding balls. It promotes the precipitation of preferred microstructural phases and consequently better mechanical properties. The scope of this work is to study the effect of the austenitization temperature on the tribological behavior of forged steel balls intended for raw material grinding in cement industry. Three austenitization temperatures are used: 870°C, 950°C and 1150°C. A normal load of 10 N is applied to estimate the wear mechanism induced during a travel of 20 meter. Microhardness measurements, optical and SEM macrographs and 3D roughness views measurements are carried out on the generated wear grooves for each heat treatment test. The obtained results relate the effect of the heat treatment temperature and the applied force on the tribological behavior of the studied samples.Voir les détails

Mots clés : steel, forging, grinding balls

Characterization of DD1 Algerian Kaolin and the Effect of  Potassium Salts on Mullitisation of Kaolinite.

A. Grid, N. TOUATI, A. MEBEREK, H.REZZEG, S. BOUCHOUCHA (2019)
Article de conférence

Abstract. This work aims to characterize local Kaolin from Djebbal Dbagh (DD1), Guelma, Algeria, in raw state and after being sintered to improve its refractoriness by mullitisation of the main phase known as kaolinite in order to exploit DD1 as a basic material to elaborate refractory bricks. The characterization of DD1was carried out by different methods of analysis such as chemical analysis, XRD, DTA/TG analysis and scanning electron microscopy (SEM). Furthermore, the measurement of some physical properties such as apparent density, porosity and microhardness of sintered material was performed. The mullitisation was tested without and with addition of potassium salts such as K<sub>2</sub>CO<sub>3</sub>, KNO<sub>3</sub> and K<sub>2</sub>SO<sub>4</sub> as mineralizers to find out the effect of these salts on transition phase from kaolinite to mullite and the inhibition of cristobalite existence versus sintering temperature from 1300&deg;C to 1450&deg;C. The influence of these mineralizers at the cited temperatures was evaluated using XRD. The results show that the additives K<sub>2</sub>CO<sub>3</sub> and KNO<sub>3</sub> have an effective role to accelerate the formation of mullite which is considered as the most favorite phase for high refractoriness.Voir les détails

Mots clés : mullitisation, kaolinite, refractory bricks, characterization, Sintering

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

Elaboration et caractérisation de céramiques ZnO-TiO2.

Alima MEBREK (2018)
Thèse de doctorat

L'orthotitanate de zinc (Zn2TiO4) de structure spinelle inverse a été préparée par la méthode solide en deux étapes. La première étape consiste à broyer mécaniquement un mélange de poudres de ZnO et TiO2 avec un rapport molaire de 2:1 dans un broyeur planétaire à haute énergie sous atmosphère d'argon. Les poudres broyées ont été ensuite calcinées à 900°C pendant 2 heures, puis pressées en pastilles et frittées pendant 4 heures à 1100°C à l'air. La formation des phases, la microstructure, la morphologie de surface et les propriétés optiques ont été étudiées par diffraction des rayons X, spectroscopies Raman, infrarouge à transformée de Fourier (FT-IR), microscopie électronique à balayage couplée à la spectroscopie à rayons X à dispersion d'énergie (EDX), microscopie à force atomique et spectrophotométrie UV/visible. Les résultats des rayons X de la poudre broyée pendant 6 h révèlent la présence de Zn2TiO4 nanocristallin (15,5 %, = 13,2 nm), en plus de l'anatase a-TiO2, ZnO et le rutile r-TiO2. La fraction volumique de la phase Zn2TiO4 augmente avec le temps de broyage. Les pastilles présentent une structure composite dans laquelle une petite quantité de nanograins de rutile r-TiO2 est dispersée dans la matrice de titanate de zinc Zn2TiO4. Les résultats des spectroscopies FT-IR et Raman confirment le caractère biphasique des pastilles. La microstructure de la pastille 18 h est assez propre avec une répartition homogène de la taille des grains par rapport à celle de la pastille 6 h qui présente peu de pores. La rugosité de surface (r.m.s) des pastilles diminue avec l'augmentation du temps de broyage. L'énergie de la bande interdite des pastilles 6 h et 18 h est de l'ordre de 3,22 eV et 3,45 eV, respectivement. Voir les détails

Mots clés : Broyage mécanique, Système ZnO-TiO2, DRX, SEM

Preparation and characterization of spinel type Zn2TiO4 nanocomposite.

Alima MEBREK, Safia ALLEG, Sihem BENAYACHE, Mohamed BENABDSLEM (2018)
Article de journal

Zinc orthotitanate Zn2TiO4 spinel structures have been prepared by solid state reaction in two stages. First, a mixture of ZnO and TiO2 (67% anatase+33% rutile) in a molar ratio of 2:1 was mechanically milled for 6 and 18 h, at room temperature, in a high energy planetary ball mill under argon atmosphere. Next, the ball milled powders were calcined at 900°C for 2 h, pressed into pellets and then sintered for 4 h at 1100°C in air. Phase formation, microstructure, surface morphology and optical properties were characterized by X-ray di?raction, Raman scattering spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, atomic force microscopy and UV–visible spectro- photometery. The mechanical milling process for 6 h gives rise to the formation of nanocrystalline orthotitanate Zn2TiO4 (15.5%, =13.2 nm) in addition to unreacted rutile TiO2, anatase TiO2 and ZnO structures. As the milling process progresses up to 18 h, the volume fraction of Zn2TiO4 increases to about 44.5%. The sintered pellets exhibit a composite structure where about a small amount of rutile nanograins are dispersed into the Zn2TiO4 matrix. FT-IR and Raman results con?rm the biphasic character of the sintered pellets. The band gap energy is milling time dependent. It varies from 3.22 for pellet 6 h to 3.45 for pellet 18 h.Voir les détails

Mots clés : Mechanical Alloying, ZnO−TiO2 system, XRD, Raman spectroscopy, SEM

Puzzle of c-WN phase stabilization

W. RICHI, D. ZANATI (2018)
Article de conférence

In this paper, we present first-principles calculationsthat compare structural and electronic properties of WN inthe NaCl and NbO phases. Our results predict that the NbOstructure of WN is more stable than the NaCl structure withoutdefects, where the enthalpy of formation per formula unit Hf =-0.872eV and 0.616eV for NbO and NaCl structures, respectively.Moreover, the calculated lattice parameters of c-WN are a=4.35A°and a=4.11A° for NaCl and NbO phases, respectively. It is veryclear that the lattice parameter obtained for c-WN in NbO is invery good concordance with that reported experimentally of a =4.14A° . Although the formation energy calculations support thehypothesis of the stability of the NbO phase, the experimental xrayphotoelectron spectroscopy (XPS) electron density of statesfor valence band spectra corresponds to that density of statescalculated for c-WN in NaCl phase. Based on this comparison,more consideration must be taken into account to elucidate thisissue.Voir les détails

Mots clés : Cubic Tungsten nitride ceramics, Firstprinciples calculations, Formation energy

DEVELOPMENT AND CHARACTERIZATION OF HYDROXYAPATITE FOR BONE USE

A. Azzi, L. Bahloul, L. Alimi, S. Guerfi, S. Bouyeg, M. Boulkra, A. Grairia (2018)
Article de conférence

The objective of this work is the elaboration of a biomaterial Hydroxyapatite (Ca10 (PO4)6 (OH)2), by a synthetic method of precipitation, (CaCl2, 2H2O) as source of calcium and (Na2HPO4, 12 H2O) as a source of phosphate. After preparation, the powder was calcined at 900 °C for 90 minutes at a speed of 10 °C / min and compacted into pellets 12 mm in diameter and 2 mm thick. Sintered powder at different temperatures (1000 °C, 1100 °C, 1200 °C, and 1300 °C). In order to study the effect of sintering temperature on the microstructure, the physical and morphological properties of the elaborated hydroxyapatite, the density, the porosity, X-ray diffraction (DRX) and the scanning electron microscopy (SEM) were used for the characterization of the powder. The density decreases with the increase of the porosity, in fact the sample densifies easily when the porosity is lowerVoir les détails

Mots clés : hydroxyapatite, SEM, DRX, Porosity, Density

INVESTIGATION OF THE EFFECT OF ALUMINUM ALLOY POSITION ON RESIDUAL STRESSES IN DISSIMILAR FSW WELD BY USING THE ULTRASONIC METHOD

I HADJI, R Badji, M Gaceb, N KHARROUBA, L RABAHIL (2018)
Article de conférence

The main goal of this study is to show the effect of the advancing side (AD) and the retreating side (RT) position on the Residual stresses and local mechanical behavior of dissimilar friction stir welds of aluminum alloys AA2024-T3 and AA7075-T6. Different samples were produced by varying the rotational speed of the tool (1200 and 1400 rpm) and the alloy position regarding the advancing side of the tool. Ultrasonic Method has been used to evaluate Residual Stresses. Method ultrasonic is based on the acoustoelastic effect, which measures the velocity variation of the elastic waves according to the stress state of the material. This can be achieved through a calibration test, which permits the determination of the acoustoelastic coefficient (K). A tensile stress show in heat affected zone (HAZ) and a compression stress in the base metal (BM). Increasing the rotational speed reduces the amplitude of the longitudinal residual stresses with a high reduction in the case where AA7075 - T6 is in the advancing side whit 1400 rpm. This has been directly associated to the increase in the heat input and the reduction of the thermal mismatch between different areas of the weld. The microstructure effect of aluminum alloy position acts on the acoustoelastic constant K. The choice of t0 corrects the overestimated residual stresses in the (HAZ) and (N).Voir les détails

Mots clés : residual stresses, FSW, Aluminum alloy, Dissimilar welding