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Artykuły w czasopismach na temat "Carbure de tungstène – Teneur en cobalt"
Liao, H., i C. Coddet. "Relations entre la microstructure et le comportement à l’abrasion des cermets carbure de tungstène-cobalt." Revue de Métallurgie 91, nr 9 (wrzesień 1994): 1366. http://dx.doi.org/10.1051/metal/199491091366.
Pełny tekst źródłaRozprawy doktorskie na temat "Carbure de tungstène – Teneur en cobalt"
Agode, Kofi Edoh. "Analyse et modélisation du comportement à l’usure des outils de coupe en carbure de tungstène pour différentes teneurs en cobalt lors de l’usinage de l’alliage de titane Ti-6Al-4V". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0141.
Pełny tekst źródłaDue to their high hardness and wear resistance, cemented carbide (WC-Co) is the main material used to manufacture machining tools and forming tooling, as well as wear parts requiring high hardness and high precision. The modification of tungsten carbide microstructure, and more particularly its cobalt content, is currently attracting the greatest interest from manufacturers to develop new grades tools with high performance, and then expand new markets.This thesis aims to study the effect of the cobalt content of carbide tools on the measured values and wear mechanisms when machining hard superalloys such as the aeronautical titanium alloys Ti-6Al-4V. Both experimental and numerical research work are devoted on one hand to the understanding of the microscopic damage mechanisms leading to the macroscopic wear of the WC-Co composite and on the other hand, to the influence of the cobalt content on the behavior of the WC-Co taking into account the mechanical-microstructure-damage coupling.On the basis of an experimental analysis, the identification of the macroscopic and microscopic physical phenomena involved at the tool/chip and tool/workpiece contact interfaces was conducted. Machining tests were firstly carried out on the tool-material couple WC-Co/Ti-6Al-4V with different cobalt contents for the tools (from 6 to 15%). In a second step, a tribological characterization of the same tool-material couple was carried out to evaluate the influence of the cobalt content and the contact conditions (sliding speed, applied force) on the friction coefficient and wear. However, the inaccessibility of the contact zones during machining and the tribological tests did not allow a complete description of the wear mechanisms observed, whether macroscopic mechanisms (adhesion, abrasion, deformation, ...), or microscopic mechanisms (cracking, damage of the WC and Co phases). The numerical simulation using finite elements (FE) proved to be a very interesting complementary tool for the analysis of these wear mechanisms.Our modeling strategy focused on the response of WC-Co at the microstructure scale for the thermomechanical loading close to that obtained by machining. The proposed model takes into account the behavior of the WC and Co phases separately and that of the interfaces WC-WC and WC-Co of the composite. This strategy allowed to study and identify parameters influencing the behavior of the microstructure from the elastic stage to the damage initiation. A good agreement was obtained between the results of the numerical behavior at the initiation of damage in the microstructure and those of the experimental observations in terms of the effects of the cobalt content in the tungsten carbide and of the applied machining conditions
Barré, Thierry. "Modification des propriétés de surface du carbure de tungstène fritté cobalt en vue du dépôt de diamant par CVD". Toulouse, INPT, 2000. http://www.theses.fr/2000INPTA17C.
Pełny tekst źródłaMoche, Hélène. "Utilisation du carbure de tungstène-cobalt (WC-Co) comme témoin positif génotoxique nanoparticulaire et étude de la génotoxicité de candidats nanovecteurs de médicaments". Thesis, Lille 2, 2014. http://www.theses.fr/2014LIL2S024/document.
Pełny tekst źródłaNanomaterials are used in many industrial sectors, and many nanomaterial-containing consumer products are already available. In this context of increasing human exposure to nanomaterials, the evaluation of their genotoxicity is of significant importance. However, the relevance of routinely used genotoxicity assays, developed for non-nanoparticular products, is often questioned for the evaluation of nanomaterials. A nanoparticulate reference positive control would therefore constitute an important step to a better testing of nanomaterials genotoxicity, ensuring that test systems are actually appropriate and/or allowing the validation of new ones.Firstly, we studied the possibility of using commercially-available tungsten carbide-cobalt (WC-Co) nanoparticles, previously characterized for physicochemical properties (size distribution and charge in used media), as positive control in three in vitro genotoxicity assays. The mouse lymphoma thymidine kinase gene mutation assay, the micronucleus assay studying chromosomal aberrations and the comet assay detecting primary DNA damage were performed. The last two assays were realized in two cell types, the mouse lymphoma cell line L5178Y and primary cultures of human lymphocytes. Our results show that WC-Co nanoparticles could be used as positive control in these in vitro genotoxicity assays, according to cell type and treatment schedule.Secondly, we investigated the mechanisms of action involved in WC-Co nanoparticles genotoxicity. Detection of centromeres in micronuclei using fluorescence in situ hybridization (FISH) show the involvement of both clastogenic and aneugenic activities. This was correlated with the results of a chromosome aberration assay on human lymphocytes blocked in metaphase, showing chromatid breaks and polyploid cells. Moreover, as oxidative mechanisms are the most described for nanomaterials, we studied oxidative DNA damage using the modified in vitro comet assay with the DNA repair enzyme formamidopyrimidine DNA glycosylase (FPG). We also detected a production of hydroxyl radicals using electron paramagnetic resonance in suspensions of WC-Co nanoparticles with and without cells. While performing high-throughput assays on WC-Co nanoparticles in three human cell lines corresponding to the main target organs for nanomaterials (A549 lung cell line, Hep3B liver cell line and Caki-1 kidney cell line) it was confirmed that oxidative stress play a significant role in the toxicity of WC-Co nanoparticles. Indeed, the production of reactive oxygen species in cells exposed to WC-Co nanoparticles was correlated to the observation of cytotoxicity and genotoxicity, studied using the detection of γH2AX foci.Finally, we carried out the most relevant genotoxicity assays to study nanodiamonds and lipid nanocapsules, which constitute promising nanovectors for drug delivery. The in vitro comet and micronucleus assays were performed on other cell types mimicking target organs: the T84 intestinal epithelial cell line and the 16-HBE bronchial epithelial cell line exposed to nanodiamonds of three different sizes, and human lymphocytes exposed to lipid nanocapsules of three different sizes and three different charges
Marou, Alzouma Ousseini. "Durabilité tribologique de matériaux pour insert de dents de tunnelier". Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0042.
Pełny tekst źródłaThe frequency of maintenance operations during the excavation of the ground by the tunnel boring machines (TBM) is problematic for civil engineering companies. These maintenance operations provoke expensive timeouts and they bring in excavation operators in risky hyperbaric work conditions. One of the reasons which leads to the numerous human interventions for the maintenance is the damage of drag bits located on the cutting wheel of the TBM. These drag bits undergo wear due to the abrasiveness of the various media they meet. The purpose of this thesis is to contribute to increase by 20 % at least the lifetime of the materials of the dag bits, in order to reduce the various maintenance operations which expose the operators to important risks. To achieve this goal, the investigations led in this work concerned several axes. At first, an expertise is led to identify the wear modes prevailing on the carbide inserts located on the drag bits; then, new materials with enhanced mechanical properties and optimized microstructures, developed in the framework of the European project NeTTUN, are characterized on representative lab testing devices. These tests allowed us to understand well the wear mechanisms of the newly developed grades of tungsten carbides. The results of this work can lead to new strategies for the selection of materials to reinforce the drag bits
Pellan, Maxime. "Développement des joints de grain et des joints de phase dans les carbures cémentés WC-CO". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI121/document.
Pełny tekst źródłaWC-Co cemented carbide is a two phase system constituted of a cobalt based binder matrix embedding hard tungsten carbide grains. This material is especially used in fields such as metal cutting or mining, where high mechanical properties are required. Therefore, the microstructure is a key parameter to control to optimize the mechanical properties of the alloy.This work aims at understanding the mechanisms of grain boundary and phase boundary development during sintering, and how they may influence the final microstructure. The effect of the binder content, carbon content and sintering time was especially investigated.Electron BackScattered Diffraction characterization was chosen to conduct this study. First because the precise separation of grains in the resulting images makes possible automation of the measurements, and thus allows a statistical analysis of several microstructural parameters (as grain size, contiguity) on numerous samples. Secondly because orientation data collected by this way make possible the analysis of grain boundary and phase boundary texture. To this end, an automated method was developed for analysis of grain boundaries and estimation of remarkable boundary planes fraction from 2D EBSD measurements.The study of contiguity shows that it does not depend on sintering time or carbon content in the binder, but essentially of the carbide grain volume fraction. This result implies that impingement is the first order parameter in the evolution of contiguity. Grains appear to grow faster and in a larger extent in samples with a carbon rich binder, as well as in high binder content samples. Abnormal grain growth seems to be favored by high binder content in carbon rich samples. All grain boundaries were characterized by a couple of rotation axis and misorientation angle. Three particular rotation axes were identified: [101 ̅0], [21 ̅1 ̅0] and [0001]. They represent around 30% of the total grain boundary surface area. In addition, specific rotations were found to be particularly abundant in the microstructure: [101 ̅0]/90°, [21 ̅1 ̅0] / (48°- 60°- 90°) and [0001]/90°.A study of their geometry suggests that their stability would be due to a particularly coherent boundary plane. A statistical analysis shows that most grain boundaries and phase boundaries have a habit plane parallel to a basal or prismatic plane (about 70% of the total grain boundary surface area and 50% of the total phase boundary area. Finally, a scenario is proposed for the microstructure development model during sintering of cemented carbides on the basis of the results