The aim of this study is focused on the experimental investigation of dynamic wear behavior of carbon black filled rubber compounds comprising pristine styrene butadiene rubber (SBR) together with incorporated SBR ground rubber (rubber powder). We also analyzed and described quantitatively the service conditions of some dynamically loaded rubber products, which are liable to wear (e.g. conveyor belts, tires). Beside the well-known standard test method to characterize wear resistance at steady-state conditions, we used an own developed testing equipment based on gravimetric determination of mass loss of rubber test specimen to investigate the influence of rubber powder content on dynamic wear depending on varying impact energy levels. Incorporation of SBR rubber powder in SBR rubber compounds increases wear. With increasing rubber powder content the wear at steady-state conditions progressively increases. However, the level of wear at dynamic loading conditions increases only once, but stays constant subsequently even with contents of incorporated rubber powder.

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

Made available in DSpace on 2016-12-08T17:19:34Z (GMT). No. of bitstreams: 1 1 Capa Elisangela.pdf: 88134 bytes, checksum: 928630a2b7c7c224aabda5bd1bfe3ecc (MD5) Previous issue date: 2009-12-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work, termochemical nitriding treatments (plasma nitriding, gas nitriding and solid nitriding) were performed in tool steels (AISI H13, AISI P20 and N-8550), with the objective to compare and evaluate the tribological performance and the acquired properties on these three processes and prove the solid nitriding efficiency. Wear tests were conducted in a convencional pin-on-disk apparatus, we obtained the friction coefficient and the amount of wear, with the use of a profiling equipment. The samples were transversally cut after the wear test, and then analysed through microhardness and scanning electron microscopy to verify the formation of nitriding typical layers (white layer and diffusion layer). X- Ray Difratometry proved the presence of the fases Fe4N - _´ and Fe2,3N _. The results showed that solid nitriding presented good performance, promoting the formation of a nitriding layer with compatible microhardness when compared with the other processes and the best results of wear. The higher disadvantage faced was the irregularity in the thickness of the formed layer. / Neste trabalho, tratamentos termoquímicos de nitretação (nitretação a plasma, nitretação gasosa e nitretação sólida) foram aplicados em aços ferramenta (AISI H13, AISI P20 e N-8550), com o objetivo de comparar e avaliar o desempenho tribológico e as propriedades adquiridas nos três processos e comprovar a eficiência da nitretação sólida. Testes de desgaste foram conduzidos em equipamento convencional de pino sobre disco, foram levantados o coeficiente de atrito e o volume de desgaste, esta avaliada com o auxílio de um perfilômetro. As amostras foram cortadas tranversalmente após o teste de desgaste, sendo posteriormente analisadas através de microdureza e microscopia eletrônica de varredura, para verificar a formação das camadas típicas de nitretação (camada branca e de difusão). Difratometrias de Raios X comprovaram a presença das fases Fe4N - _´ e Fe2,3N - _. Os resultados mostraram que a nitretação sólida apresentou boa performance, proporcionando a formação de uma camada nitretada com microdureza compatível à obtida nos outros processos e os melhores resultados de desgaste. A maior desvantagem encontrada foi a irregularidade da espessura da camada formada.

The aim of this study is focused on the experimental investigation of dynamic wear behavior of carbon black filled rubber compounds comprising pristine styrene butadiene rubber (SBR) together with incorporated SBR ground rubber (rubber powder). We also analyzed and described quantitatively the service conditions of some dynamically loaded rubber products, which are liable to wear (e.g. conveyor belts, tires). Beside the well-known standard test method to characterize wear resistance at steady-state conditions, we used an own developed testing equipment based on gravimetric determination of mass loss of rubber test specimen to investigate the influence of rubber powder content on dynamic wear depending on varying impact energy levels. Incorporation of SBR rubber powder in SBR rubber compounds increases wear. With increasing rubber powder content the wear at steady-state conditions progressively increases. However, the level of wear at dynamic loading conditions increases only once, but stays constant subsequently even with contents of incorporated rubber powder.

Le remplacement des alliages durs à base cobalt par des alliages à base fer suscite un intérêt croissant pour la protection anti-usure des pièces métalliques fonctionnant dans le circuit primaire d’une centrale nucléaire. Dans le cadre de cette thèse, une étude métallurgique détaillée a été effectuée sur des dépôts épais en Norem 02™ élaborés par le procédé de projection laser.Un affinement significatif de la microstructure du Norem 02™ a été obtenu après optimisation des paramètres du procédé (puissance laser, vitesse de balayage et débit de poudre), par rapport à un procédé concurrent par Plasma à Arc Transféré. Les essais tribologiques montrent que l’amélioration de la microstructure n’empêche cependant pas l’apparition du grippage à 300°C.La deuxième partie de cette étude a été consacrée à l’amélioration du Norem 02™ avec ajout de différents éléments chimiques. Le choix de ces ajouts adéquats a été validé grâce aux tests de frottement réalisés sur des échantillons en Norem 02™ modifié, sous haute contrainte mécanique (1 GPa) et à haute température (300°C). Parmi une dizaine d’éléments d’ajouts testés, l’ajout de titane a permis une transformation complète de la microstructure du Norem 02™. Cette transformation métallurgique a amélioré son comportement tribologique avec un faible coefficient de frottement (<0.3) à 300°C.L’origine de cette amélioration du comportement mécanique du Norem 02-Ti a été étudiée et expliquée par différentes analyses microstructurales (MO, MEB, EDS, EBSD) ainsi que des essais de traction sur des éprouvettes extraites des revêtements épais. / This study aims to substitute the cobalt-based hardfacing alloys with iron-based hardfacing alloys to protect mechanical parts operating in the primary circuit of a pressurized water reactor (PWR)Firstly, a detailed metallurgical study was carried out to characterize a thick deposit on Norem 02™ produced by the laser process (Direct Metal Deposition - DMD). Compared with a classical PTA process, a microstructure refinement was achieved after an optimization of process parameters (laser power, scanning speed and powder flow-rate). However, wear tests show that the improvement of the microstructure does not prevent the occurrence of galling at 300 ° C.The second part of this study is dedicated to Norem 02™ improvement with the addition of various chemical elements. The appropriate additions to this application have been validated by wear tests under high mechanical stress (1 GPa) and at high temperature (300°C). Among a dozen samples of modified Norem 02 ™, the addition of titanium was shown to provide a complete transformation of the initial Norem 02™’s microstructure. This metallurgical transformation improved its tribological behavior with a low friction coefficient (<0.3) obtained at 300 °C.Last, the origin of the mechanical behavior improvement of Norem 02-Ti was studied and explained by microstructural analysis (MO, MEB, EDS, EBSD) and tensile tests on specimens extracted from thick coatings.