L’augmentation de la vitesse ferroviaire impose l’amélioration des performances de freinage liés aux matériaux de friction utilisés dans les freins à disques et à semelles. Cependant, l'usure reste un point limitant en terme de performance mais aussi de sécurité. Elle a pour conséquence de détériorer les matériaux (aspects mécano-thermiques) mais aussi de contaminer le contact entre roue et rail par des particules de semelles de frein pouvant isoler électriquement celui-ci (aspects mécano-électriques). Le procédé permettant de localiser les trains, ayant pour principe la conduction électrique entre roue et rail, est alors compromis.Ces problématiques sont gouvernées par les différents contacts (roue/rail, roue/semelle, ...) qui s'inscrivent dans le concept de triplet tribologique. Un triplet est composé des corps en contact (premiers corps), de l'interface (troisième corps) et du mécanisme qui les maintient en contact. Afin de comprendre les phénomènes se produisant au sein des contacts, une analyse multi-physique locale et un découplage des paramètres (mécaniques, thermiques, électriques) s'avèrent nécessaires. Toutefois, cela est difficile à établir expé- rimentalement, une modélisation numérique par éléments discrets est alors pertinente pour palier à ces besoins.L'écoulement dynamique d'un troisième corps constitué de particules de freinage et la dégradation d'un matériau de freinage réel (suite à des méthodes d'imageries) sont modélisés. Les résultats obtenus ont permis d'appréhender les compétitions existant entre paramètres physiques d'une part (mécanique, électrique, thermique) et paramètres d'éch-elles d'autre part (local, global). Ces compétitions tendent à minimiser la résistance élec- trique lorsque les constituants sont en proportion adéquat (meilleure conduction électrique entre roue et rail) mais aussi à équilibrer les débits du circuit tribologique, ce qui conduit à protéger les matériaux (usure contrôlée). En outre, les analyses numériques ont permis de mettre en évidence de nouveaux paramètres liés à ``l'étalement'' du troisième corps et d'appréhender les points clés permettant de se rapprocher d'un contact réel. / The increase of the rail speed imposes the improvement of the braking performances related to the friction materials used in brake pad and brakes shoes. However, wear remains a limiting point in terms of performance but also safety. It has the effect of damaging the materials (mechano-thermal aspects) but also to contaminate the contact between wheel and rail by particles of brake shoes that can electrically isolate it (mechanical-electrical aspects). The method for locating the trains, whose principle is the electrical conduction between wheel and rail, is then compromised.These issues are governed by the different contacts (wheel/rail, wheel/shoes, ...) that fit into the concept of tribological triplets. These are composed of the bodies in contact (first bodies), the interface (third body) and the mechanism that keeps them in contact. In order to understand the phenomena occurring within the contacts, a local multi-physics analysis and a decoupling of the parameters (mechanical, thermal, electrical) are necessary. However, this is difficult to establish experimentally, numerical modeling by discrete elements method is then relevant for these needs.The dynamic flow of a third body consisting of braking particles and the degradation of a real braking material (following imaging methods) are modeled. The results obtained made it possible to understand the competitions existing between physical parameters on the one hand (mechanical, electrical, thermal) and scale parameters on the other hand (local, global). These competitions tend to minimize the electrical resistance when the constituents are in adequate proportion (better electrical conduction between wheel and rail) but also to balance the flows of the tribological track, which leads to protect the materials (controlled wear). In addition, the numerical analyzes made it possible to highlight new parameters related to "spreading" of the third body and to apprehend the key points making it possible to approach a real contact.

Les exigences actuelles en terme de lubrification automobile imposent des formulations extrêmement complexes. Parmi tous les additifs présents dans l’huile, on peut noter le dithiocarbamate de molybdène et le dithiophosphate de zinc, additifs à action tribologique, à base de soufre et de phosphore. Pour des raisons environnementales, il est important de diminuer nettement voire d’éliminer la présence de ces deux éléments dans les huiles. Les matériaux à base de carbone présentent des propriétés tribologiques intéressantes mais n’ont jamais été entièrement étudiés. Dans cette étude nous nous sommes intéressés aux propriétés lubrifiantes des nanotubes de carbone (NTCs). Des nanotubes multi-parois ont été dispersés dans l’huile puis les propriétés rhéologiques et tribologiques des « nanolubrifiants » ont été étudiées. Nous nous sommes intéressés à leurs propriétés tribologiques dans deux régimes de lubrification : le régime limite et le régime élastohydrodynamique. Nous nous sommes tout d’abord focalisés sur les propriétés rhéologiques du mélange huile/NTCs.Les nanotubes de carbone possèdent une tendance à s’agréger sous la forme d’un réseau de taille micrométrique ce qui résulte en une nette augmentation de viscosité de l’huile de base. Cet effet épaississant pourrait éventuellement permettre aux NTCs de remplacer une partie de l’Améliorant d’Indice de Viscosité (AVI) habituellement additionné à l’huile de base. Néanmoins, nous avons mis en évidence un effet antagoniste avec les autres additifs de lubrification, tel que le dispersant, qui pourrait être un problème pour une telle utilisation. Nous nous sommes ensuite intéressés aux propriétés des NTCs dans le régime limite de lubrification. Les NTCs présentent des propriétés réductrices de l’usure et du frottement intéressantes sous certaines conditions. Les analyses effectuées laissent supposer un rôle du catalyseur dans le mécanisme de lubrification. Les nanotubes de carbone semblent d’un grand intérêt car, ils possèdent également des propriétés tribologiques en régime élastohydrodynamique (EHD). Le mécanisme de formation des films lubrifiants a été étudié en fonction des paramètres concentrations et vitesses d’entraînement: la propagation des agrégats de NTCs à travers le contact résulte en une augmentation locale de l’épaisseur de film lubrifiant. De plus, une réduction de frottement et un décalage dans l’apparition des premières traces d’usure ont été observés à la suite d’essais tribologiques. Le mécanisme d’action des NTCs en régime de lubrification EHD est proposé dans cette partie. Cependant, les interactions entre les NTCs et les additifs présents dans les lubrifiants entièrement formulés doivent être étudiés pour optimiser la formulation de lubrifiant à base de nanotubes de carbone. / The current requirements in automotive lubrication impose extremely complex formulation. Among all the additives present in oil, one can note the presence of molybdenum dithiocarbamateand zinc dithiophosphate, both tribological additives containing sulfur and phosphorous. For environmental reasons, it is important to reduce or eliminate the presence of these two elements contained in oil. Carbon based materials are expected to present interesting tribological properties but were never really fully investigated. In this study, we are being interested on the lubricant properties of nanometric Carbon NanoTubes (CNT). Multi wall carbon nanotube MWNTs have been dispersed in oil and the behaviour of the blends has been studied in terms of rheology and tribology. We investigated their friction properties in two regims of lubrification : boundary lubrification and elastohydrodynamic (EHD) lubrification. At first, we focused in rheological properties of the blend. Carbon NanoTubes (CNT) present the tendency to aggregate to form micrometric network and this results in an increase in the blend viscosity. This thickening effect could make it possible to replace part of the ViscosityIndex Improver traditionally added to base oil. Nevertheless we reported an antagonist effect with other additives such as dispersant which may be a problem for this purpose. Then we investigated lubricant properties of CNT in boundary regim. CNTs show interesting friction reducing and anti-wear properties in some conditions. The results obtained let suppose a role of the catalyst in the lubrication mechanism. CNT are also of great interest in reason of their potential tribological properties in EHD lubrification regim. The lubricant film formation has been investigated as a function of the speed and the CNT concentration : the propagation of the CNT through the contact results in a local increase in the film thickness. Moreover, a reduction in friction and a drift in the wear onset have been observed under controlled contact kinematics. A potentiel mechanism of lubrification is explained in this last part. However, the interaction between the carbon nanotubes and the other additives present in the fully formulated lubricant need to be carrefully investigated in order to be able in the future to optimise the formulation of new carbon nanotubes based lubricants.

Dans ce travail de thèse, une amélioration aussi bien à l’échelle globale qu’à l’échelle locale a été apportée sur la compréhension des mécanismes tribologiques aux interfaces outil-pièce-copeau durant l’usinage à sec de l’acier C45 avec des outils en carbure de tungstène revêtus en TIN. Dans une première partie expérimentale, des essais de frottement ont permis d’étudier la sensibilité des paramètres de frottement sur le comportement tribologique aux interfaces pion-pièce. Ainsi, l’évolution du coefficient de frottement, du flux de chaleur et du coefficient de partage de chaleur aux interfaces outil-pièce-copeau ont été identifiés pour le couple de matériau frottant et frotté. Pour mieux comprendre ces phénomènes, une étude métallographique a été effectuée sur des échantillons. Elle a notamment permis l’obtention des transformations métallurgiques au niveau de la surface superficielle de la pièce : des affinements des grains (déformation plastique) aux basses vitesses de frottement et des couches blanches (durcissement thermique) pour les grandes vitesses. Pour avoir plus de détails, un modèle numérique simulant l’essai de frottement a été développé en se basant sur l’approche Arbitraire Lagrangienne Eulérienne (A.L.E). Ce modèle nous a permis d’avoir plus d’informations sur les grandeurs locales de frottement (pression de contact, température de contact, vitesse locale de glissement, déformation plastique). Un modèle de frottement et un modèle de coefficient de partage de chaleur ont été identifiés à travers cette étude numérique. Dans la deuxième partie expérimentale, deux types d’essais d’usure ont été effectués dans des conditions similaires sur des pions et sur des plaquettes d’outils de coupe de même nuance. Des analyses microscopiques et au MEB couplés à une analyse EDS ont été faites afin de mieux analyser les mécanismes tribologiques durant les essais d’usure. Des similitudes de faciès d’usure ont été observées à différentes échelles d’analyse, sur les pions ainsi que sur les plaquettes d’outils de coupe. Ces similitudes ont permis d’aboutir à une corrélation des phénomènes tribologiques observés sur les pions et ceux observés sur les plaquettes. / In this work, improved both global and local levels has been made on understanding the tribological mechanisms at the chip-tool-workpiece interface in dry machining of a AISI 1045 steel with a TiN coated carbide tool. In the first part, several friction tests have been performed to study the sensitivity of friction parameters on the tribological behavior at pin-workpiece interface. Thus, evolutions of the apparent friction coefficient, of heat flux and of heat flux partition ratio have been identified. To better understand these phenomena, a metallographic study was performed on the samples of the workpiece.It has enabled the achievement of metallurgical transformations in terms of surface area of the room : the refinement of grains (plastic deformation) friction at low speeds and white layers (thermal curing)for high speeds. These results show that the initial state of the steel (ferritic-pearlitic microstructure) has been changed, In fact, two phenomena have been observed. The first phenomenon has been observed for low sliding velocities. In this range of the sliding velocities, the grains have been crushed because of the large plastic deformations. The second phenomenon has been observed by increasing the friction velocity. In fact, the white zones have been identified at the surface layer and which have presented a different structure compared to the initial state of the steel. A 3D A.L.E. numerical model, simulating the friction test, enables to extract local information from the contact area, especially the contact pressure, the contact temperature and the average local sliding velocity. An adhesive friction model and a heat partition coefficient model depending on average local sliding velocity have been identified. These friction models can be utilized in a FEM of the cutting process in order to improve the understanding of the material flow and temperature distribution around cutting tools. In the second part, pin wear in the friction tests and tool wear in machining tests have been performed. To compare the phenomena observed at the tool-chip interfaces during the wear tests in machining with the phenomena observed at the pin-workpiece during the wear tests of friction, similarities of faces have been observed at different scales of analysis on the pins and on the cutting tool inserts.

Friction and wear have been observed m mechanical systems when there is a relative motion between two solid bodies Friction mainly results in loss of energy and wear results in matenal loss The proper understanding of friction and wear mechanisms provides practical solutions to tribological related problems Various models are available m tribology literature to calculate function coefficient and wear rate of matenals However, expenments suggest that these models are incomplete and fortuitous as the tnbological response is system dependent The objective of present investigation is to understand the tribological lesponse of commercially puie titanium and OFHC copper pins sliding on polyciystallme alumina discs Di\ shdm% tests were conducted in air, and vacuum (1 5 x 10~2Pa) at room tempeiatuie under different experimental conditions The normal load was vaned from 15 3 N to 76 0 N, sliding speed was vaned from 0 01 ms"1 to 1 4 ms"1, and tempeiatuie was varied from 293 K to 793 K It is found that the haidness of metals do not have any effect on their tribological response The experimental obseivations indicate that tribological response of metals mainly depends up on miciostructural evolution, oxygen activity and relative shear strength of metals and ceramics Chapter 1 starts with the background and concepts of tribology A brief literature survey is given with published work in relation with the present work In Chapter 2, the experimental proceduies of the dry sliding test and compression test are given Chapter 3 explains the tribological response of titanium during shdmg against alumina Different wear mechanisms such as oxidation, deformation and adhesion were identified Deformation wear mechanism is explained using strain rate response approach Chapter 4 explains the tribological response of copper during sliding against alumina The influence of environment and microstructural evolution on its tribological behavior are studied Chaptei 5 explains the dependence of tribological response of metals on micro structural evolution, oxygen activity and relative shear strength of metals and ceramics This thesis ends with the conclusions of the present investigation

Selective laser melting (SLM) is a powder-based additive manufacturing technique consisting of the exact reproduction of a three dimensional computer model (generally a computer-aided design CAD file or a computer tomography CT scan) through an additive layer-by-layer strategy. Because of the high degree of freedom offered by the additive manufacturing, parts having almost any possible geometry can be produced by SLM. More specifically, with this process it is possible to build parts with extremely complex shapes and geometries that would otherwise be difficult or impossible to produce using conventional subtractive manufacturing processes. Another major advantage of SLM compared to conventional techniques is the fast cooling rate during the process. This permits the production of bulk materials with very fine microstructures and improved mechanical properties or even bulk metallic glasses. In addition, this technology gives the opportunity to produce ready-to-use parts with minimized need for post-processing (only surface polishing might be required). Recently, significant research activity has been focused on SLM processing of different metallic materials, including steels, Ti-, Ni- and Al-based alloys. However, most of the research is devoted to the parameters optimization or to feasibility studies on the production of complex structures with no detailed investigations of the structure-property correlation. Accordingly, this thesis focuses on the production and structure-property correlation of Al-12Si samples produced by SLM from gas atomized powders. The microstructure of the as-prepared SLM samples consists of supersaturated primary Al with an extremely fine cellular structure along with the residual free Si situated at the cellular boundaries. This microstructure leads to a remarkable mechanical behavior: the yield and tensile strengths of the SLM samples are respectively four and two times higher than their cast counterparts. However, the ductility is significantly reduced compared with the cast samples. The effect of annealing at different temperatures on the microstructure and resulting mechanical properties of the SLM parts has been systematically studied by analyzing the size, morphology and distribution of the phases. In addition, the mechanical properties of the SLM samples have been modeled using micro- structural features, such as the crystallite and matrix ligament sizes. The results demonstrate that the mechanical behavior of the Al-12Si SLM samples can be tuned within a wide range of strength and ductility through the use of the proper annealing treatment. The Al-Si alloys are generally used as pistons or cylinder liners in automotive applications. This requires good wear resistance and sufficient strength at the operating temperature, which ranges between 373 – 473 K. Accordingly, the tensile properties of the SLM samples were also tested at these temperatures. Changing the hatch style during SLM processing vary the texture in the material. Hence, samples with different hatch styles were produced and the effect of texture on their mechanical behavior was evaluated. The results show that the hatch style strongly influences both the mechanical properties and the texture of the samples; however no direct correlation was observed between texture and mechanical properties. The wear properties of the Al-12Si material was evaluated using pin-on-disc and fretting wear experiments. These experiments show that the as-prepared SLM samples exhibit better wear resistance than their cast counterparts and the SLM heat-treated samples. Finally, the corrosion investigations reveal that the SLM samples have similar corrosion behavior as the cast specimens under acidic conditions. A major drawback for the wide application of SLM as an industrial processing route is the limited size of the products. This is a direct consequence of the limited dimensions of the available building chambers, which allow for the production of samples with volumes of about 0.02 m3. A possible way to overcome this problem would be the use of the welding processes to join the small SLM objects to form parts with no dimensional limitations. In order to verify this possibility, friction welding was employed to join Al-12Si SLM parts. The results indicate that friction welding not only successfully permits the join materials manufactured by SLM, but also helps to significantly improve their ductility. This work clearly demonstrates that SLM can be successfully used for the production of Al-12Si parts with an overall superior performance of the mechanical and physical properties with respect to the conventional cast samples. Moreover, the mechanical properties of the SLM samples can be widely tuned in-situ by employing suitable hatch styles or ex-situ by the proper heat treatment. This might help the development of SLM for the production of innovative high-performance Al-based materials and structures with controlled properties for automotive and aerospace applications.

Made available in DSpace on 2014-06-11T19:34:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2005Bitstream added on 2014-06-13T19:04:58Z : No. of bitstreams: 1 souza_jvc_dr_guara.pdf: 3439864 bytes, checksum: 8f665815b08c108458b7f10749c5f6bb (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Nesse trabalho foram desenvolvidas três composições à base de Si3N4 com quantidades e tipos de aditivos diferentes, com objetivos de desenvolver cerâmicas densas de altas resistências, para posteriores testes como ferramentas de corte na usinagem de torneamento do ferro fundido cinzento, ferro fundido vermicular e a liga Ti-6Al-4V. As composições utilizaram aditivos Y2O3/Al2O3 (10%) e AlN/Y2O3 (15 e 20%), e foram sinterizadas pelo processo de sinterização normal. Em seguida foram caracterizadas quanto as propriedades físicas e mecânicas, apresentando bons resultados. Posteriormente a composição de melhores propriedades (SNYA20), foi transformada em inserto para usinagem de corte de acordo com a norma ISO 1832. Os testes de torneamento foram realizados no ferro fundido cinzento com variações de parâmentros, onde para Vc=300m/min, f=0,32mm/rot e ap=1,00mm, alcançou um comprimento de corte de 6533m, superior aos encontrados em literatura, com diminuição dos desgastes, para maiores Vc e ap. O torneamento da liga Ti-6Al-4V em alta velocidade (Vc=180m/min, f=0,10mm/rot e ap=0,50mm), alcançou comprimento de corte de Lc=466m, para um desgaste VBmax=2,20mm. No torneamento do ferro fundido vermicular, com variações de parâmetros, alcançou resultados superiores aos encontrados na literatura com ferramentas cerâmicas comercial, utilizando Vc=200mm/min, f=0,20mm/rot e ap= 0,50mm, obteve-se comprimento de corte Lc=1658m. Os resultados de usinagem obtidos nesse trabalho estão relacionados com as propriedades e fases obtidas. Entretanto alem dos resultados obtidos essas ferramentas apresentam custo em torno de 50% das comerciais e redução de 17- 20% de custo no processo, devido ao uso de fluido refrigerante e proteção ao meio ambiente. / In this work three compositions to base Si3N4 with amounts and types of different additives had been developed, with objective to develop dense ceramics of high strength to possible test as cutting tools in turning of gray cast iron, compacted graphite iron and titanium alloy (Ti-6Al-4V). The compositions had used additives Y2O3/Al2O3 (10%) and AlN/Y2O3 (15 and 20%), and were sinterized by process normal sintering. After sintering the physical and mechanical properties had been characterized, showing interesting results. Posterior the composition the best properties (SNYA20), was transformed into cutting tools to machining in the stand norm ISO 1832. The turning tests had been carried in gray cast iron with different parameters, where to Vc=300m/min, f=0,32mm/rev and ap=1,00mm, obtained a cut length of 6533m, achieving value superior at found in literature, with important reduction to larger cutting speed and cut depth. The turning of the Ti-6Al-4V alloy in high cutting speed (Vc=180m/min, f=0,10mm/rev and ap=0,50mm), obtained cutting length of Lc=466m, to VBmax=2,20mm. In turning compacted graphite iron, with different parameters, obtained value superior at found in literature, when utilize cutting tools ceramics of commercial materials, using for this Vc=200mm/min, f=0,20mm/rev and ap = 0,50mm. These condition obtained cut length of Lc=1658m. The results achieved in this work have been associated with the important physical and mechanical proprieties and phase of cutting tools. However the results obtained with these cutting tools present lower cost (50%) when compared with commercial cutting tools of similar material e reduction of cost in around 17-20%, because the do not use coolant, beside of protection at environment.

Made available in DSpace on 2016-12-08T17:19:17Z (GMT). No. of bitstreams: 1 Anael Krelling.pdf: 4334549 bytes, checksum: 5f6d37933553590fff7bc05b902644dc (MD5) Previous issue date: 2012-06-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work, solid boriding thermochemical treatment was carried out using Ekabor® 1-V2 and one blend as boriding agents and heat treatment of quenching and tempering of AISI H13 tool steel in order to compare and evaluate the tribological behavior and the properties acquired for four studied conditions, that were: Ekabor® powder boriding, Ekabor® powder boriding followed by quenching and tempering, boriding with a blend as boriding agent and quenched and tempered condition. Sliding wear tests were performed in pin-on-disc apparatus in order to evaluate the friction coefficient and the volume of material removed (measured with the aid of a profiling equipment). After the wear tests the samples were transversally cut for metallographic evaluation by optical and scanning electron microscopy. X-ray diffraction was used to confirm the formation of borided layer. The results showed that the boriding treatments, regardless the boriding agent used, are effective in increasing wear resistance. The thickness of borided layer was greater for boriding with Ekabor® powder than the blend agent, this one, nevertheless, showed significant improvement in wear resistance compared to the quenched and tempered condition. There are several wear mechanisms that take place in the sliding wear test but the adhesive wear mechanism was reduced by boriding treatment. / Neste trabalho foram realizados tratamentos termoquímicos de boretação por via sólida com pó comercial Ekabor® 1-V2 e mistura boretante, além de tratamentos térmicos de têmpera e revenimento em aço ferramenta AISI H13 com o intuito de comparar e avaliar o comportamento tribológico e as propriedades adquiridas para quatro condições estudadas, sendo elas: boretação com pó Ekabor®, boretação com pó Ekabor® seguida de têmpera e revenimento, boretação com uma mistura como agente boretante e condição apenas temperada e revenida. Testes de desgaste por deslizamento foram realizados em tribômetro de pino-sobre-disco para avaliação do coeficiente de atrito e volume de material removido (avaliado com o auxílio de perfilômetro). Após os ensaios de desgaste as amostras foram cortadas transversalmente para avaliação metalográfica através de microscopia óptica, microscopia eletrônica de varredura e microdureza. Os mecanismos de desgaste foram analisados por microscopia eletrônica de varredura. Difratometria de raios-X foi utilizada para a comprovação da formação da camada de boretos. Os resultados mostraram que o tratamento de boretação, independentemente do agente boretante utilizado, é eficaz no aumento da resistência ao desgaste. A espessura das camadas de boretos foi maior para boretação realizada com pó Ekabor® em comparação com a mistura boretante, esta última, apesar disto, apresentou melhoria significativa em comparação com a condição de têmpera e revenimento. Vários são os mecanismos de desgaste que ocorrem no ensaio por deslizamento sendo que o mecanismo de desgaste por adesão foi reduzido com a realização dos tratamentos de boretação.

Made available in DSpace on 2016-12-08T17:19:20Z (GMT). No. of bitstreams: 1 Lucas Selonke Klaas.pdf: 5855700 bytes, checksum: f10fd37619590a5b128a3aec7c9e878c (MD5) Previous issue date: 2013-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / With the purpose of reduce wear in plain bearings, in initial turning periods, was evaluated tribologically the sintered metal patent in relation to the cast which is used in commercial bearings. In the present study have been conducted experiments using the dilatometer to determine the optimal temperature and time for sintering the white metal. In the sintered specimens was measured by scanning electron microscopy the sinterability. The need for this preliminary study is due to the difficulty in sintering of this alloy is as much difference in melting temperature between the three elements. Sliding wear tests were performed in tribometer pin-on-disc for evaluating the coefficient of friction and volume of material removed (as measured with the aid of profilometer) and compared with the white metal obtained by melting and bronze obtained by sintering. The wear mechanisms were analyzed by scanning electron microscopy. Of all configurations evaluated, the sintered bronze lubricated showed lower wear and sintered white metal lubricated had the lowest coefficient of friction. / Com o objetivo de reduzir o desgaste em mancais de deslizamento nos períodos iniciais de giro, foi avaliado tribologicamente o metal patente sinterizado como opção do fundido que é utilizado em mancais comerciais. No presente trabalho foram realizados experimentos com o dilatômetro para determinar a melhor temperatura e o tempo de sinterização para o metal patente. Nos corpos de prova sinterizados avaliou-se por meio do microscópio eletrônico de varredura a sinterabilidade. A necessidade desse estudo prévio dá-se pela dificuldade da liga na sinterização, pois há grande diferença de temperatura de fusão entre os três elementos. Aconteceram testes de desgaste por deslizamento com tribômetro de pino sobre disco para a análise do coeficiente de atrito e do volume de material removido (verificado com o auxílio de perfilômetro), além de depois terem sido comparados com o metal patente obtido por fundição e com o bronze oriundo da sinterização. Os mecanismos de desgaste foram observados por microscopia eletrônica de varredura. De todas as configurações examinadas, o bronze sinterizado lubrificado apresentou menor desgaste, e o metal patente sinterizado lubrificado teve o menor coeficiente de atrito

Made available in DSpace on 2016-12-08T17:19:21Z (GMT). No. of bitstreams: 1 Mario Augusto Morozo.pdf: 3275631 bytes, checksum: 146bb363d630204d1f0a795658dce502 (MD5) Previous issue date: 2013-08-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work, solid boriding thermochemical treatment was carried out using Ekabor® 1-V2 and heat treatment for hardening and tempering hot work tool steel AISI H13 in order to compare and evaluate the tribological behavior and properties acquired for four conditions studied, namely: boriding with Ekabor used powder ® 1-V2, boriding with Ekabor new powder ® 1-V2, quenched and tempered, and as supplied (annealed). Fixed-ball Microabrasive wear tests were performed to evaluate the steady-state wear, wear coefficient, wear volume and friction coefficient. After wear tests, the samples were transversally cut for metallographic evaluations by optical microscopy and microhardness. The wear mechanisms were analyzed by scanning electron microscopy. X-ray diffraction was used to confirm the formation of a borided layer. The results showed that the layer formed after the boriding with Ekabor ® 1-V2 used powder had become quite uneven, which may directly influence in reducing the wear resistance. The same irregularity was detected after boriding with Ekabor® 1-V2 new powder. However, for this second condition, in all áreas, thicker layer was noted. The quenched and tempered condition had the highest average wear coefficient, followed by the annealed condition and boride powder Ekabor ® 1-V2 used, whose coefficients were virtually identical. The boride with Ekabor new powder ® 1-V2 had the lowest average wear coefficient. / Neste trabalho foi realizado tratamento termoquímico de boretação por via sólida com pó comercial Ekabor® 1-V2 e tratamento térmico de têmpera e revenimento em aço ferramenta para trabalho a quente AISI H13 com o intuito de comparar e avaliar o comportamento tribológico e as propriedades adquiridas para quatro condições estudadas, sendo elas: boretação com pó Ekabor® 1-V2 usado, boretação com pó Ekabor® 1-V2 novo, condição temperada e revenida e condição como fornecida (recozida). Ensaios de desgaste microabrasivo foram realizados em equipamento de microabrasão do tipo esfera fixa para avaliação da obtenção do regime permanente de desgaste, coeficiente de desgaste, volume de desgaste e coeficiente de atrito. Após os ensaios de desgaste as amostras foram cortadas transversalmente para avaliação metalográfica através de microscopia óptica e microdureza. Os mecanismos de desgaste foram analisados por microscopia eletrônica de varredura. Difratometria de raios-X foi utilizada para a comprovação da formação da camada de boretos. Os resultados mostraram que a camada formada após a boretação com pó Ekabor® 1-V2 usado apresentou-se bastante irregular, o que pode ter influenciado diretamente na redução da resistência ao desgaste. A mesma irregularidade foi verificada após a boretação com pó Ekabor® 1-V2 novo. Entretanto, para esta segunda condição, em todas as regiões se observou uma espessura de camada maior. A condição temperada e revenida apresentou o maior coeficiente de desgaste médio, sendo seguida pelas condições recozida e boretada com pó Ekabor® 1-V2 usado, cujos coeficientes foram praticamente idênticos. A condição boretada com pó Ekabor® 1-V2 novo apresentou o menor coeficiente de desgaste médio.

These Graduation Theses solve effects of tribological behaviour of materials pairs on the basic of the SIGMA GROUP a.s. requirements. For available materials there was a target to design tribological pairs and check their behaviour.