Métallurgie
Caractérisation microstructurale et micromécanique d’unassemblage X60/316L, réalisé par Cladding, après déformation par laminage à chaud.
The objective of this work is to study the behavior of an assembly composed of a high yield strength steel and an austenitic stainless steel made by the cladding process under the effect of hot working followed by recrystallization annealing. Microstructural and micromechanical characterizations were performed on the whole multi-material and at the interface. In the present work, we have highlighted the importance of understanding and mastering the aspects of phase transformation and recrystallization mechanisms in order to optimize the mechanical properties by thermal and/or thermomechanical treatment. Voir les détails
Mots clés : Cladding, HSLA steel, stainless steel, thermomechanical treatment, recrystallization, phase transformation, Microhardness, annealing.
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
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
Heat Treatment Effect on the Microstructural, Hardness and TribologicalBehavior of A105 Medium Carbon Steel
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
Study of The Structure and Corrosion Behavior of Al-15%MoAlloy
The influence of the addition of molybdenum on the structure and corrosion behaviour of aluminium was studied using optical microscopy, scanning electron microscope (SEM),potentiodynamic polarization and electrochemical impedance spectroscopy. The results showthat the addition of 15%wt molybdenum causes the precipitation of the Al12Mo intermetallic phase which appears in plate form on the αAl matrix. The results of the electrochemical tests show that the addition of molybdenum displaces the corrosion potential of aluminium towards positive values from -699 mV/ECS to -633 mV/ECS and increases the charge transfer resistance from to 4752 Ω.cm2 to 6608 Ω.cm2. Voir les détails
Mots clés : corrosion, Al-15%MoAlloy, Electrochemical behavior
Synthesis and tribocorrosion performances of multilayer (Ta/ZrN)n coatings
Multilayer thin coatings (~3 µm in thickness) were deposited using reactive radio frequency magnetron sputteringon Ti-6Al-4 V substrate for biomaterial applications. Films are a combination of hard zirconium nitride with pure tantalum, used to manage interfacial stress and to avoid crack growth. Alternating hard/ductile material is a biomimetic design inspired by nature(nacre-inspired materials). Tribocorrosion tests were performed in Hank’s solution at 37 C, under open circuit potential by using a ball-on-disk reciprocating tribometer. A tendency to high resistance against corrosion was found for all the samples. Coatings with a top 100 nm thick ZrN layer showed more noble potential as well as a reduction of both the friction coefficient and the wear rate during the sliding phase. The principal wear mechanism is related to a tribocorrosion layer formation. Voir les détails
Mots clés : Multilayer coating, Biomaterial, Tribocorrosion, Tantalum, Zirconium nitride, Magnetron sputtering
Mechanical properties and bio‑tribological performance of PVD (Ta/ZrN)n multilayer coatings on UHMWPE in bovine serum lubrication
This work investigated the tribological performance of (Ta/ZrN)n multilayer coatings against ultrahigh molecular weight polyethylene (UHMWPE) material. Three multilayer coatings with different designs were deposited on Ti-6Al-4V substrate and subjected to wear testing under lubrication of diluted bovine calf serum. The results revealed an improvement in wear resistance of (Ta/ZrN) multilayer coatings and low coefficient of friction under an applied load of 1 N. High hardness, excellent biotribological properties, and low residual stresses were obtained in the multilayer coating with the thinnest ZrN as the topmost layer of 100 nm. This work demonstrates that Ta/ZrN multilayers can be promising coatings for prosthesis applications. Voir les détails
Mots clés : PVD coating, Ta/ZrN, UHMWPE, wear
Surface peformances of PVD ZrN coatings in biological environments
Zirconium nitride (ZrN) thin films were deposited by reactive RF magnetron sputtering on Ti-6Al-4V and Si (100) substrates for potential use in biomedical applications. The tribological behaviour was evaluated against bovine bone in dry condition using a pin-on-disc apparatus. Abrasion is the primary wear mechanism observed in ZrN/bone contact. The corrosion properties were determined through two electrochemical techniques: potentiodynamic polarization and electrochemical impedance spectroscopy. The coatings with reduced oxygen content provided: (i) good resistance against corrosion when exposed to physiological solution and (ii) better anti-bioadhesion against Staphylococcus aureus bacteria. Voir les détails
Mots clés : PVD coating, ZrN, wear, corrosion, bioadhesion
Effect of erosion parameters on the surface direction texture-Study by experimental plans
The aim of this work is to study the effect of solid particle impact erosion parameters of sand on the isotropy parameter "Std" which presents the direction of surface texture. The experimental methodology adopted for this experimental work is the Box Behnken plan with three factors, each at three levels (-1, 0 and +1), the parameters considered are: time "t", pressure "P" and angle of impact "θ". 3D roughness measurements were carried out using a laser source profilometer type Cyper-Technologie-CT100, in order to characterize the different surfaces after erosion test. The statistical analysis was carried out using the Mini Tab software, where a mathematical model was established showing the relationship between the input parameters (t, P, θ) and the output parameter "Std". This model predicts the "Std" response in the field of study as well as the parameters of the sandblasting regime. The results show the significant effect of the impact angle on "Std" and the interaction between the different parameters in the study domain, of which the highest value of "Std" is equal to 130 ° for an average time combined with low pressure and impact angle. Voir les détails
Mots clés : erosion, topography, roughness surface, Mathematical model, Box plans