Métallurgie
Influence of dry friction on the wear behavior of X52steel—experimental study and simulation using response surfacesmethod
Friction and wear phenomena alter the behavior of the material surface, where certain relevant parameters which characterizethe surface are influenced. Therefore, the objective of this work is to identify the parameters most influencing the frictioncoefficient (f), the wear rate (Ws), and the volume parameters (Vmc and Vvv) during the friction test. The friction tests werecarried out by adopting the methodology of 23complete planes with three factors (D, V, and Py), at two levels each. Theresults show a decrease in the wear rate when all three factors are at their highest level and a decrease in the friction coefficientwhen using minimum load on speed long distances. In addition, the mathematical models developed allow to reveala correlation between the test parameters (D, V, and Py), and the responses studied (f, Ws) in their study field. Moreover,the volume parameters Vmc and Vvv were evaluated during the tests, and the morphology of the worn surface shows thatthe friction under a load of 1 N leads to the predominance of an abrasive wear mechanism, while a load of 10 N promotesan adhesive wear mechanism. Voir les détails
Mots clés : Complete plans, modeling, friction coefficient, Wear rate, volume parameters
On the evolution of microstructure, texture and corrosion behavior of ahot-rolled and annealed AZ31 alloy
The microstructure and texture evolution of an AZ31 alloy were investigated after hot rolling and subsequentannealing using electron backscatter diffraction (EBSD). First, the alloy was hot-rolled at 350 ? C up to low,medium and high strain (20, 50 and 85% of thickness reduction, respectively). The alloy samples where thenannealed at 350 ? C for 2, 10 and 60 min. The effect of strain level and annealing on corrosion behavior inseawater was also evaluated using electrochemical tests. At low strain, the microstructure was characterised bythe absence of twinning, mainly due to the prior thermo-mechanical history of the as-received alloy. However,various modes of twinning were observed at medium strain. At high strain, the dynamic recrystallization processresulted in a microstructure with a typical basal texture. The results demonstrate that twins are responsible forthe deviation of {0002} basal poles from normal towards the transversal direction. Annealing at 350 ? C for up to60 min led to normal grain growth in all the samples. In medium and highly strained samples, the deformationtexture was retained, while the low strain sample underwent noticeable changes due to the absence of dynamicrecrystallization. A synergetic effect of grain refinement and texture weakening was responsible for the alloy’senhanced corrosion resistance.AZ31 alloyCorrosionDynamic recrystallizationStatic recrystallizationRolling Voir les détails
Mots clés : AZ31 alloy, corrosion, Dynamic recrystallization, Static recrystallisation, rolling
Dissimilar welding of aluminum alloys 2024 T3 and 7075 T6 by TIG process with double tungsten electrodes
The aim of this work is to study the metallurgical and mechanical properties of dissimilar assemblies of 2024 T3 and 7075 T6 structural hardening aluminum alloy by the TIG twine electrode arc welding process. It will include a weld performed according to optimized welding parameters followed by a study of the macroscopic and microscopic evolution of the dissimilar assembly (2024-7075) using optical and scanning electron microscopy (SEM); in addition, the phase compositions were analyzed with an energy dispersive spectrometer (EDS). Tensile and microhardness tests were performed. The tensile fracture was observed by SEM. This paper suggests that when the double tungsten electrode TIG welding is used, a stable arc has been formed with a good bead appearance. The heat dissipated by the arc generates several zones (molten zone (WZ), bonding zones (LZ), heat-affected zones (HAZ)) with different microstructures or precipitates of the type θ (Al2 Cu), S (Al2 Cu, Mg) and η (Mg Zn2), S (Al2 Cu Mg) are formed in the heat-affected zone (HAZ) of base metals 2024 and 7075 respectively. The microhardness is lower in the molten zone and higher in the heat-affected zone of 7075 T6 alloy, which cried out an embrittlement and a 44% and 37% drop in the tensile strength of 7075 T6 and 2024 T3 base metals respectively. Voir les détails
Mots clés : 2024 and 7075 aluminum alloy, Aluminum with structural hardening, microstructure, Double electrode TIG processing, Dissimilar welding
Plastic Deformation Effect on Wear and Corrosion resistance of Super Martensitic Stainless Steel
The microstructure and the mechanical properties of a super martensitic stainless steel (SMSS) were investigated in this study. Test specimens were taken from seamless tube generally used in oil and gas industries. The specimens were plasti- cally deformed by tension from its as-received state to different levels of elongation at 2%, 10%, and 15%, respectively. The focus was to study the influence of plastic deformation on the tribological behavior against alumina balls in dry conditions and the corrosion resistance in 3.5% NaCl solution. Analysis results showed an abrasive wear as the main wear mechanism. Plastic deformation prior to sliding wear test increases wear resistance as the deformation rate increases. Based on the elec- trochemical experiments, all of the specimens showed an increase in their corrosion resistance i.e., the corrosion potential Ecorr (vs. Ag/AgCl) tends to move toward more noble values with respect to the initial potential. The greatest polarization resistance was displayed by the specimen with 10% of deformation rate. Voir les détails
Mots clés : Super Martensitic Stainless Steel, • Cold deformation, • Wear, • Corrosion
Investigation ?n Dry Sliding Wear Performance and Corrosion Resistance of 13Cr5Ni2Mo Supermartensitic Stainless Steel
This work aimed to study the microstructure, wear and corrosion resistance of supermartensitic stainless steel (SMSS). Heat treatment applied to samples consists of quenching after austenitization at elevated temperature (1250 °C) followed by a double tempering at 650 °C. Conventional mechanical properties, scanning electron microscopy (SEM/EDS) analysis and X-ray diffraction methods (XRD) are used to analyze the microstructure and to evaluate the wear mechanisms. The potentiodynamic polarisation and the electrochemical impedance spectroscoopy (EIS) methods are used to evaluate the corrosion resistance in both the 0.5M H2SO4 and 0.5M NaCl aggressive media. The microstructure is mainly composed with tempered lath martensite, small quantity of retained austenite and carbides. Oxidative and abrasive wear dominated the wear process in dry condition. During the corrosion process, the same mechanism of degradation was found in both the 0.5M NaCl and 0.5M H2SO4. Voir les détails
Mots clés : Supermartensitic steel, microstructure, friction, Wear Corrosion
Élaboration par pulvérisation cathodique magnétron de couches minces en vue de leur utilisation comme biomatériaux. Caractérisation à l’usure et à la corrosion
The design and development of biomaterials with multifunctional surfaces by magnetron sputtering is the final objective of this work. Different mechanical and structural properties of the films obtained in monolayers (ZrN and Ta) and in multilayers (Ta / ZrN) were determined and analyzed. Investigative tools were X-ray diffraction (DRX), optical microscopy (OM) and scanning electron microscopy (MEB) and atomic force microscopy (AFM).Mechanical properties such as nanoindentation, stress measurements and adhesion tests were also carried out. The tribological and electrochemical performances of the different coatings were analyzed and compared. The Ar / N2 + O2 ratio in the plasma shows a negative influence of the O2 on the performances in wear and corrosion of ZrN Less oxygen leads to better results. The results obtained on multilayer ZrN/Ta coatings with different thicknesses show that they have intermediate properties to those of the monolayers that constitute them. Mechanical and tribological properties, low coefficient of friction of the Ta layer and good wear resistance of the ZrN layer. The M2 multilayer coating (ZrN/Ta) having the thickness of the layers which decreases with the increase in the number of periods has the best mechanical characteristics highlighted by scratch test and nanoindentation. Voir les détails
Mots clés : Biomaterials, PVD, tribology, corrosion
Caractérisation morphologique et mécanique deu polyéthylène semi cristallin extrudé
La tuyauterie en polyéthylène a haute densité (PEHD) sont utilisés pour la conduite d'eau potable marqué par un trait bleu, et la conduite du gaz naturel de ville marqué par un trait jaune. Le but de cette étude et de caractérisé ces matériaux morphologiquement et surtout mécaniquement, due a un taux de crisallinté remarquable, qui sera quantifié par plusieurs méthodes de caractérisations. cette cristallinité est causé par son historique de fabrication qui est l'extrusion. Voir les détails
Mots clés : Polymere, PEHD, extrusion, Cristallinité, DSC
CARACTERISATION DE LA GROSSEUR DES GRAINS DANSLES MATERIAUX SOLIDES PAR ONDES ACOUSTIQUES
Les ultrasons ont prouvé leur efficacité dans le domaine de lacaractérisation non destructive des matériaux. Leur application se diversifie dejour en jour. Outre leur application dans le domaine industriel. Les ultrasons offrentune fiabilité certaine dans la caractérisation non destructive des propriétésphysiques, mécaniques et chimiques Voir les détails
Mots clés : taille de graine
Correlation Between the Pitting Potential Evolution and σσ Phase Precipitation Kinetics in the 2205 Duplex Stainless Steel
The aim of this work is to correlate the pitting potential (Epit) evolution with the kinetics ofrphaseprecipitation in the 2205 duplex stainless steel aged at 850°C after solution treatment at 1150°C. Thepotentiodynamic polarization curves indicate a reduction of the pitting corrosion resistance with the agingtime, which is revealed by a decrease in theEpitvalues from 0.65 to 0.40 VSCE. Thus,Epitvalues are used todetermine the kinetics parameters of therphase precipitation. The experimental transformed fractionagrees well with the one calculated by using the modified Kolmogorov–Johnson–Mehl–Avrami equationwith an impingement parameterc= 0.6. Voir les détails
Mots clés : kinetic, KJMA, Pitting corrosion, otentiodynamic polarization, r phase precipitation
Isothermal and non-isothermal precipitation kinetics in Al–Mg–Si-(Ag) alloy
In the present work, isothermal and non-isothermal precipitation kinetics in a 6063 aluminium alloy containing a small silver (Ag) addition have been investigated using Vickers microhardness and Differential Scanning Calorimetry (DSC) measurements respectively. Isothermal kinetics analysis showed that β'' phase precipitation obeyed the Johnson-Mehl-Avrami (JMA) model. The DSC analysis revealed that Ag addition modified the precipitation sequence in the investigated 6063 aluminium alloy through the formation of an additional metastable pre-β'' phase. An approach based on the additivity concept has been applied to the heating DSC diagrams to investigate the β'' phase precipitation. The obtained Avrami exponent values from this approach led to suggest that the β'' phase precipitation proceeded through two processes during continuous heating. The Avrami exponent value obtained at the final stage of the transformation was consistent with that obtained from the isothermal analysis, whereas the corresponding activation energy was higher than the one calculated from the isothermal analysis and Kissinger's method. It was also established that the precipitation kinetics of the β'' phase was enhanced by the formation of the precursor phase pre-β''. Voir les détails
Mots clés : 6063 aluminium alloy, Ag addition, Precipitation kinetics, JMA model, Additivity concept