Sciences et génie des matériaux
EVALUATION OF MECHANICAL STRESS EFFECT ON THE PROPERTIES OFSTAINLESS STEEL SURFACES BY SECM, SKP, SVET AND LEIS
Mechanical stress or fatigue cracks originate from varioussurface imperfections, such as inclusions, pits, or residualstress. It is very important to use a method to predict thelikelihood of environment-assisted cracking or pitting corrosion.The austenitic stainless steel shows high corrosionresistance level. It knows that plastic deformation decreaseit's resistance. The corrosion form in case of this steel is veryspecial and the corrosion tests are difficult. The investigationof Scanning Kelvin Probe (SKP), s canning vibrationelectrode technique (SVET) and localized electrochemicalimpedance spectroscopy (LEIS) to evaluate the influence ofmechanical stress on the electrochemical properties ofaustenitic stainless steel 316L.We tested the selected steel about its corrosion behaviour afterhigh rate deformation. We wanted to find a relationshipbetween the corrosion resistance decreasing and the rate ofthe plastic deformation. Plastic deformation effect of thecorrosion resistance in case of austenitic stainless steel Voir les détails
Mots clés : SKP, SVET, LIES, corrosion, austenitic, plastic deformation 316
Extraction of green inhibitor and study of their antioxidant effectiveness of ecologicalcorrosion
Several methods are available to prevent or retard corrosion ofmetallic materials, the use of inhibitors is one of the besttechnique to ensure their protection in contact with aggressivemedia such as hydrochloric acid medium. The environmentaltoxicity of organic corrosion inhibitors has prompted thesearch for green corrosion inhibitors as they are biodegradable,do not contain heavy metals or other toxic compounds. As inaddition to being environmentally friendly and ecologicallyacceptable, plant products are inexpensive, readily availableand renewable. The objective of this work is the extraction oflimonene from orange peels and study their effectiveness onthe corrosion of X42 steel in HCl medium. The analysis ofinhibitor was evaluated by chemical methods, and theelectrochemical study shows that the addition of limonene tothe medium induces a reduction in the corrosion rate of thesteel in HCl medium. Other parameters may influence itsinhibitory activity such as immersion time, concentration ofinhibitor, the nature of media (acidic or basic). Voir les détails
Mots clés : Metal and alloys; Acid medium; corrosion inhibitors; Green inhibitors; limonene
Valuation of mill scale as iron pigments for painting anticorrosive.
The mill scale is a steelmaking byproduct. This work focuses on the valuation of the steel waste and its transformation to a usable product in the field of anti-corrosion paints. These iron oxides have been examined as a pigment and corrosion inhibitor in two types of paints with different concentrations (1 %, 3 %, 7 %, and 15 %) to determine the best formulation. Their properties were compared to that of an anticorrosion paint trademark based on iron oxide. For this purpose various techniques of mechanical and physical-chemical analysis were used; grinding is applied to pieces of mill scale for very fine powders (< 32 μm); the particle size of the milled scale analysis, to determine their particle size distribution; a primary electrochemical method used to evaluate the performance and scale vis-à-vis the phenomenon of corrosion behavior, and a UV-Visible spectroscopic method for determining the concentration of total dissolved iron. The experimental results showed that the anti-corrosion properties or rather inhibition efficiency increases with increasing concentration of the mill scale in the tested paints. Voir les détails
Mots clés : mill scale, corrosion inhibitor, spectroscopic, electrochemical analysis
Effect of brazing current on microstructure and mechanical behavior of WC-Co/AISI 1020 steel TIG brazed joint
In this work, the WC-Co carbide/1020 steel brazed joints which were prepared by Tungsten Inert Gas (TIG) process using different brazing currents have been studied. The peak temperature reached by increasing the brazing current caused remarkable inter-diffusion of Ni, Mn, Cu and Co elements between the braze and the base materials. The higher the brazing current was, the larger the diffusion extent of these elements became and the greater the WC rearrangement occured. As the diffusion rate of Ni towards the WC-Co was enhanced through increasing brazing current, a short range diffusion of Co element towards the braze was recorded. A Special Shear Test (SST) conducted at room temperature revealed the best bonding strength for the current of 80A. Besides, hardness (HIT) and elastic modulus (EIT) values of the interfaces were situated between those of the braze and the base materials. Voir les détails
Mots clés : WC-Co cemented carbide, TIG brazing, inter-diffusion, Interface, Nano-indentation
Etude du comportement tribologique des alliages de fonderie
Le présent travail, fait l’objet de l’étude de comportement tribologique de deux alliages de fonderie : un acier austénitique au manganèse Fe-14%Mn-1.2%C et un inoxydable austénitique de type AISI309. Ces deux aciers sont élaborés au niveau de la société de fonderie ALFET (Tiaret) dans un four électrique de capacité de 6 tonnes.Les échantillons ont subi après maintient à 1100°C pendant 4heures, un traitement d’hypertrempe suivi d’un refroidissement rapide à l’eau. Les essais d’usure sont réalisés à l'aide d’un tribomètre pion/disque de type Tribometer 4.4U dont les paramètres pris en considération sont: la force normale est 5 N, la bille est en acier trempé 100C6 et la vitesse linéaire est 10,05 cm/s.L’observation par MEB montre que la structure de l’acier AISI309 est composée d’une matrice constituée de gros grains austénitiques et un réseau interdendritique continu de carbures de chrome.La structure de l’acier au manganèse Fe-14%Mn-1.2%C présente deux zones austénitiques : une zone foncée riche en manganèse et l’autre claire appauvrie en manganèse.L’addition du vanadium dans l’acier austénitique au manganèse augmente sa résistance à l’usure au frottement par la diminution de coefficient de frottement de 0.45 à 0.35L’acier Fe-14%Mn-1.2%C présente une bonne résistance à l’usure par rapport à l’acier inoxydable AISI309, ceci est expliqué par la présence des précipités très fins et durs dans l’acier austénitique au manganèse. Voir les détails
Mots clés : AISI309, Acier au manganèse, tribologie, austénite.
Influence of vanadium on the corrosion behavior of high manganese steel in 0.5M H2SO4 solution
The effect of vanadium on the corrosion behavior of high manganese steel in 0.5MH2SO4 solution has been investigated using potentiodynamic polarization, linear polarization and impedance spectroscopy.The results showed that the addition of vanadium in high manganese steel decreases the corrosion current density from2.1mA.cm-2 to1.29mA.cm-2. The impedance diagrams show the existence of a single capacitive loop that is attributed to the charge transfer reaction and time constant of the electric double layer. Voir les détails
Mots clés : Vanadium, corrosion, Manganese, Impedance.
Modélisation simplifié d’un procédé de mise en forme
La prédiction de l’effort et du couple, des contraintes et des vitesses est indispensable pour conduire de façon optimale une opération industrielle comme celle de laminage. La connaissance préalable de ses grandeurs mécaniques permet la bonne mise au point d’un programme de laminage pour prévoir le bombé des cylindres, le cèdage et une consommation optimale de l’énergie. De grands progrès ont été réalisés ces dernières années dans la mise au point de codes de calculs permettant le développement de cette aspect. La méthode des éléments finis est aujourd’hui la plus utilisée, mais elle demeure lourde et demande un temps de calcul important, ce qui la rend désagréable et peu recommandable pour les industriels qui cherchent des modèles on-line pour piloter leurs opérations. Ce travail présente une contribution répondant à cette dernière exigence. Nous avons commencé par mettre au point un modèle basé sur la méthode des tranches sous environnement MATLAB. Dans la seconde étape, nous avons introduit dans ce modèle l’élasticité des cylindres et la comparaison des résultats obtenus avec ceux tirés de la littérature basée sur la méthode des éléments finis. Voir les détails
Mots clés : modélisation, simulation, Laminage, Matlab, LAM3
Fatigue properties estimation based on hardnessmeasurements and tensile properties of a dissimilar weldjoint
This work aims to estimate the high cycle fatigue properties of a dissimilar weld joint madeof 2205 duplex and 13% Cr supermartensitic stainless steels. The filler metal used is the2507 superduplex stainless steel. Two methods were used; one is a direct method thatconsists of experimental fatigue tests conducted under rotating bending conditions. Theother method is an indirect method where the fatigue properties are estimated by means ofempirical expressions based on hardness measurements and tensile properties such asYoung modulus and tensile strength. Results show that for high cycle fatigue regime, theoverall behavior of the dissimilar weld joint is controlled by the weld metal that has thelowest fatigue limit. The two base materials have the same level of fatigue limit which isslightly higher than that of the weld metal. A good agreement was obtained between thetwo used methods for the two base materials in contrast with the weld metal. Voir les détails
Mots clés : Dissimilar weld joint, fatigue, duplex, Supermartensitique, superduplex
Simulation of the propagation of cracking by finite element code calculation of a supermartensitic stainless steel pipe
The biggest concern of industrial manufacturers is the sustainability of their equipment and facilities. In the oil sector, for example, cylindrical pipe for the energy transportation to suffer corrosion damage or corrosion stress cracking is a complex problem since it requires to follow the geometry of the crack over time. Many numerical methods are applied to the propagation of fatigue cracks that require conditions to correct limitations in loading term to get results close to reality.The method of Finite Elements is a way to simulate crack propagation. However, it presents two major difficulties, the first is the use of a very fine mesh around the crack tip and the second difficulty is the explicit representation of the crack that the problem of cracking path during the simulation of propagation. Indeed, let the mesh is constructed with a priori knowledge of the route or it is changed every time the crack advance.In this context, we studied law cracking of internal pressure pipe of super martensitic stainless steel 13% Cr and 5% Ni 2% Mo by a simulation using a finite element code "ANSYS " with a calculation of the stress intensity factor and prediction of the lifetime. Voir les détails
Mots clés : simulation, Finite Elements, Crack, Pipe, Super Martensitic Stainless Steel.
Study of structural and thermal properties of SiO2 and Al2O3 in the Diatomite
Diatomite is a light colored rock formed entirely or substantially of "backbones" of diatoms. These unicellular algae are surrounded by a "shell" in silica, frustule, the accumulation of the substance can lead to the formation of a rock.In this work we determine the structural and thermal properties of SiO2 and Al2O3 in the diatomite using the plane wave method and linearized augmented (LAPW) in the functional theory of density (DFT).The potential for exchange and correlation is calculated by the generalized gradient approximation (GGA).Regarding thermal properties, we calculated the free enthalpy G, S entropy, specific heat C, thermal conductivity λ ..... etc of SiO2 and Al2O3 component. The temperatures used in this work are 1400, 1450 and 1500 respectively;The results are in good agreement with some experimental data. Voir les détails
Mots clés : DFT1, diatomite, thermal proprieties