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Nombre total de résultats : 666
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Surface performances of Ti-6Al-4V substrates coated PVD multilayered filmsin biological environments


Multilayered and nanostructured coatings of Ti based alloys (oxides and nitrides) are elaborated and tested for increasing protective properties such as corrosion and wear resistances. A pin-on-disc tribometer was used to evaluate the wear resistance in Hank's solution against bovine bone. Corrosion behavior in Hank's solution was determined by potentiodynamic and electrochemical impedance spectroscopy techniques. Besides, the specimen surfaces were characterized by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) microanalyses. The results showed that optimal tribological properties were obtained in the case of coatings having TiN as top layer. The main wear mechanism was abrasive third bodywear. In vitro corrosion tests at 37 °C showed that the better corrosion resistance was obtained when TiN was the top layer. However all of them exhibited good tribological properties, good corrosion resistance and then may be promising options for biomedical applications. Voir les détails

Mots clés : PVD coatings, oxides, Nitrides, Biomaterials, tribology, corrosion

Dry sliding wear performance of an annealed TiNi alloy with differentnickel contents

Soumaya MEDDAH, Hacene Chadli, Mounira Bourebia, Alex Montagne, Alain Iost, Mohamed Labaiz, Ahlem Taleb  (2020)

The wear behaviour of the TiNi alloy tested at different conditions (2 and 4Nas applied loads and 40,50 an 60 wt%as nickel contents) was investigated. For this purpose, two main experimentaltechniques consisting of wear and indentation tests were used. Scanning electron microscopy (SEM)and laser source profilometry were employed to reveal the wear mechanisms and the affected wornsurfaces. Furthermore, design of experiments planning introducing factorial design as well as responsesurface was adopted to attempt predicting the coefficient friction according to the planned testparameters. Nanoindentation results showed that all the TiNi alloys are harder than a TA6V4 alloywhich is commonly used in dental implant. Particularly, the TiNi60 alloy exhibited superiorsuperelasticity, characterized by a lower E/Hratio and a higher depth recovery ratio than the TA6V4alloy. Besides, the wear rates underwent a substantial increase with the increase of the applied load buta decrease with increasing the Ni content. The worn surfaces analyses revealed an enhanced resistanceto adhesive and abrasive wear with increasing nickel content. Voir les détails

Mots clés : TiNi alloy, factorial design, Wear Resistance, superplastic behaviour

Effect of ball burnishing process on mechanical propertiesand impact behavior of S355JR steel

Mounira Bourebia, Hamid Hamadache, Laouar Lakhdar, Zoheir MENTOURI, Djemili Kamila, Hazem Tarek, Taleb Ahlem  (2021)

Often, surface mechanical treatment (SMT) or heat (quenching, tempering) is used to improve the surface condition andmechanical characteristics such as impact resistance and tensile strength. Hence the objective of this experimental work, whereball burnishing (BB) as well as quenching and tempering were applied on S355 JR steel specimens, is to evaluate the surfacehardness Hv, the rupture strength Rm, the energy absorbed W during the impact test, and the work-hardened thickness e after theburnishing operation. Factorial designs were used for the test organization and mathematical models were established for theprediction of Hv, Rm, W, and “e” in function on treatment parameters considered: number of tool passes (i) and the pressure force(Py). The results show that the surface hardness increases by 30.46%. The high levels of Py and i were allowed to improve Rm by30.8% as well as an increase in tenacity of only 3.6%. Increasing the force to 20kgf promotes mixed rupture under the effect ofimpact to shock. The quenching and tempering improve the Rupture strength Rm by 183% and 119%, respectively, while theeffect of burnishing was limited to a rate of increase of this property of 28% compared to machining. Voir les détails

Mots clés : Tensile resistance . Burnishing . Heat treatment . Superficial hardness . Absorbed energy . Penetration depth . Ruptures facies

Experimental Study Of The Effect Of Shot Peening Parameters On The Surface Texture - Influence On The Adhesion Of A Paint Coating

M.Bourebia, S.Meddah, Z.Mentouri, A.Oulabbas, S.Achouri, L.Laouar  (2022)

The investigation presented in this paper focuses on the effect of surface texture on the adhesion of a paint coating as well as the influence of shot peening regime parameters on the surface isotropy indicator "Str" and on the fractal dimension "Df". The tests have been organized according to full factorial designs 23, where three parameters have been examined, at their two levels (min, max), namely the pressure (P), the angle of attack (θ) and the time (t). 3D roughness measurements have been carried out to characterize the different surfaces after a shot peening operation. A mathematical model linking the input parameters (P, θ, t) and the output parameter "Str", in the study area has been established, and the fractal dimension (Df) has been used for the surface characterization. Paint deposit has been applied to surfaces and adhesion tests have been carried out. The results show the significant effect of the impact angle on "Str", and the interaction between the different parameters in the studied area. Furthermore, the greatest bond strength has been obtained with the sample 3 (F = 4.25 N / mm2), whose the isotropy indicator "Str" is equal to 0.6438 and the fractal dimension Df = is about 1.768. Voir les détails

Mots clés : surface texture, fractal dimension, shot peening, Adhesion

Inhibition Effect of 2,2’-bipyridyl on the Corrosion of Austenitic Stainless Steel in 0.5M H2SO4


The corrosion inhibition of AISI309 austenitic stainless steel by 2,2'-Bipyridyl in 0.5MH2SO4 at 298K was studied using the mass loss’ method, the potentiodynamic polarization (Tafel), the linear polarization (LRP), and the electrochemical impedance spectroscopy (EIS). The results showed a mixed inhibition mode and an increase in the charge transfer resistance, due to inhibitor molecules' adsorption at steel surface. This latter obeys to Langmuir isotherm. The observation by scanning electron microscopy (SEM) and the analysis by energy dispersion spectrometry(EDS) confirm an inhibitor film’s presence. The calculated inhibition efficiencies are in accordance with 87.78% maximum value. Voir les détails

Mots clés : AISI309, 2, 2'-Bipyridyl, EIS, Tafel, corrosion, inhibition

Heat Treatment Effect on the Microstructural, Hardness and TribologicalBehavior of A105 Medium Carbon Steel

Amel GHARBI, Khédidja BOUHAMLA, Oualid GHELLOUDJ, Chems Eddine RAMOUL, Djamel BERDJANE, Samia CHETTOUH, Saleh REMILI  (2021)

The present work is a contribution in investigating the effect of heat treatment on microstructure, hardness, and friction wear of A105N steel. Samples of 25x25 mm² cross-section and15mm thickness have been prepared from the as-received material and then heat-treated. The samples were austenitized at 1050°C for 60 minutes followed by water quenching, then tempered at 500 and700°C for 120 minutes. Microstructural changes and their effect on the wear resistance and hardness were investigated according to the applied heat treatments. The main results show that after quenching the structure is mostly composed of quenched martensite, which confers high hardness and friction resistance to the steel. While the tempered structure is composed of tempered martensite and ferrite.As the temperature rises to 700°C, the tempered martensite decreases and is fully transformed to ferrite and cementite. A good wear resistance is expressed by a low friction coefficient and a low wear rate is achieved by tempering at 500°C. Voir les détails

Mots clés : tempering, Quenching, friction, A105, hardness, heat treatment, wear

Tribological behavior and microstructural characterization ofaustenitic stainless steel stabilized with Nb and V


This study deals with the influence of the addition of vanadium and niobium with concentrations of 1.2% and 0.14%, respectively, on the variation of the microstructure, and the tribological behavior of an AISI309 austenitic stainless steel. The studied specimens were structurally characterized by optical microscopy, scanning electron microscopy (SEM) X-ray diffraction and differential scanning calorimetry (DSC). These samples were also subjected to a tribological study using the friction wear test. The results show that the addition of vanadium and niobium causes precipitation of stable carbides (VC, NbC) which in turn causes a decrease of the chromium carbide precipitation rate. Tribological test results have also shown that the addition of these two elements improves the wear resistance of AISI309 austenitic stainless steel by decreasing the coefficient of friction from 0.824 to 0.554. Voir les détails

Mots clés : Vanadium, niobium, tribological, wear, friction, AISI309

Effect of Environmental Media on the ElectrochemicalBehavior of API X70 Pipeline Steel

A. GHARBI, B. Benayad, O. Assala, K. BOUHAMLA, O. GHELLOUDJ, S. Chettouh, S. REMILI, A. Bachiri  (2021)

This work investigates the corrosion behavior of X70 steel in different environments: sea sand, desert sand, mud, and seawater. The principle of extracting solutions from these media consisted of mixing a soil material with distilled water, and the mixture was agitated using an automatic agitator, which resulted in the extraction of the solution. Potentiodynamic polarization and electrochemical impedance tests are used to characterize the samples in both media. The results show that the pipeline steel X70 has an excellent corrosion resistance in the sea sand solution, resulting in a low corrosion current density compared to other media. The impedance diagrams for both media are characterized by two capacitive loops, the first loop is attributed to charge transfer processes and the second loop is related to diffusion phenomena. The observation of corroded surfaces shows that the corrosion mechanism in different media is by pitting. Voir les détails

Mots clés : pitting, sea sand, seawater, corrosion

A probabilistic approach to estimate the remaining life and reliability of corroded pipelines

Zelmati Djamel, BOULEDROUA Omar, GHELLOUDJ Oualid, AMIRAT Oualid, Milos B. Djukic  (2022)

Considering corrosion rate during the remaining life assessment of aging pipelines is fundamental to calculate the interval between two consecutive inspections. A total of 798 internal and external corrosion defects have been detected, using the Magnetic Flux Leakage intelligent inspection tool, over 48 km of a pipeline length located in the west region of Algeria. The statistical analysis has shown that there is a strong correlation between the corrosion defect length and the corrosion defect circumferential width, with a significant correlation coefficient equal to 82.87%. A probabilistic methodology is presented for the assessment of the remaining life of a corroded pipeline transporting gas, and a finite element method (FEM) was used to assess the pipeline failure pressure. The numerical FEM modeling results were compared with the commonly used codes-models for calculating limit pressure to establish a more realistic and accurate engineering model. The reliability analysis of an API 5L X60 steel made Algerian natural gas pipeline, in service for thirty years, and exposed to active corrosion attack, is presented. The sensitivity analysis of the basic random variables within the nonlinear limit state function was carried out to bring out the relative contribution of each variable affecting the remaining life of corroded pipelines. The reliability analysis is carried out by using Breitung’s formula, based on the second-order reliability method (SORM). The reliability assessment of the corroded pipeline is based on the usage of the notched failure assessment diagram (NFAD), different codes for the calculation of the failure pressure, and the numerical results using the finite element analyses (FEA) software ANSYS. Voir les détails

Mots clés : Corrosion defects, pipelines, Remaining life, Probability of failure, Reliability, Probabilistic approach

Reliability Estimation of Cracked API 5L X70 Pipeline Steel


The aim of this paper is to estimate the reliability of cracked pipeline steel grade API5L X70 used for hydrocarbon transportation, by coupling a developed mechanical model, basedin one hand on the simulation of cracked specimen, and an experimental result of tensile and Charpy test, and in the other hand, based on a reliability model by using a first-order reliability method (FORM). These pipes are produced by the Algerian company of manufacture of welded pipes (ALFAPIPE Annaba). The experimental task such as resilience and tensile test were carried out on specimens taken from a pipe in the longitudinal and the transversal directions. The resilience tests are carried out at different temperatures in order to estimate the fracture toughness of the material, basing on a global correlation. Besides, tensile tests are performed to bring out the mechanical characteristics of the material. After, the stress intensity factor is assessed using the analytical model of IRWIN. In the reliability analysis, the limit state function is attributed to the moment when the stress intensity factor estimated by Irwin mechanical model, is equal tothe fracture toughness of the steel pipe. The basic random variables within the limit state function are assumed to follow a normal distribution in order to simplify the assessment. Then, the evaluation of the reliability index and the parameters sensitivities of the cracked pipelines steel are assessed. Voir les détails

Mots clés : Reliability, Cracked API 5L X70, Pipeline Steel