This thesis describes a study of the influence of surface texturing on rolling contact fatigue of non-conformal contacts. The texture depth and density have been considered during experiments. It also presents the methodology and the procedure of creation of micro-dents on sample surfaces. Described results suggested that properly designed surface texturing should not necessarily increase the risk of fatigue failure of rubbing surfaces.

Ce travail de thèse concerne l’étude de différents revêtements type « Diamond-Like Carbon » élaborés par un procédé CVD assisté par un plasma basse fréquence (40 kHz). Deux revêtements de référence sont d’abord étudiés : des couches de carbone amorphe hydrogéné (a-C:H) et des couches de carbure de silicium amorphe hydrogéné (a-SiC:H). L’évolution de leurs propriétés mécaniques (dureté, module d’Young) et tribologiques (frottement, usure) est décrite en fonction des paramètres du procédé et corrélée à leur microstructure. Les résultats obtenus pour ces deux couches de référence sont ensuite exploités pour proposer deux systèmes complémentaires : des revêtements a-C:H dopées et des systèmes multicouche a-C:H/a-SiC:H. Ces deux solutions présentent des contraintes résiduelles réduites par rapport à un revêtement a-C:H monocouche ce qui permet d’envisager une augmentation importante des épaisseurs de dépôt tout en conservant des propriétés mécaniques et tribologiques intéressantes. Enfin, en vue d’une application industrielle de ces revêtements sur des pièces de moteur par exemple, l’optimisation de leur adhérence par insertion de sous-couches adaptées ainsi que de leurs performances tribologiques en conditions lubrifiées par l’intermédiaire de texturation de surface est alors envisagée / Hydrogenated amorphous carbon films (a-C:H) and hydrogenated silicon carbide films (a-SiC:H) are deposited by low frequency (40 kHz) plasma enhanced chemical vapour deposition (LF PECVD). Structural, mechanical and tribological properties of those single layers have been first studied in relation with process parameters. Then those results have been used to study two other systems. The first one corresponds to silicon doped a-C:H thin films and the second one to multilayered coatings consisting in a stack of a-C:H and a-SiC:H layers. Those coatings offer potential advantages such as lower residual stress level comparing to that of a-C:H stress level which gives the opportunity to deposit thicker films, and also attractive mechanical and tribological properties. Moreover, in case of applications like car engine parts for example, adhesion and tribological properties under lubrication have to be improved. Solutions as incorporating underlayer or texturing surface are thus also investigated in this study

Superfícies anisotrópicas lisas e rugosas foram usadas para avaliar o efeito da rugosidade e da direção de acabamento na formação de MoS2 a partir de MoDTC em ensaios tribologicos lubrificados com óleos de motor completamente formulados. Igualmente foi avaliada a resposta de atrito de lubrificantes de motor usados em carros de passageiros e em testes de dinamômetro abastecidos com etanol (E100) e gasolina (E22). Encontrou-se que tanto a direção de acabamento quanto a rugosidade foram fundamentais na reação MoDTC - MoS2. A direção de acabamento influenciou na medida que carregamentos tangenciais geram respostas diferentes nos ensaios quando são realizados paralelos e perpendiculares às linhas de acabamento, dado que para os últimos apresenta-se maior deformação plástica das asperezas, o qual favorece a obtenção de superfícies livres de óxidos, que tem sido indicada como uma condição necessário para que aconteça a reação MoDTC - MoS2. Por esta razão os valores de coeficiente de atrito próprios da formação de MoS2 foram obtidos somente nas superfícies rugosas ensaiadas perpendiculares às marcas de acabamento. Para superfícies com valores de índice de plasticidade superiores a 1 e nos quais não são formados filmes com boas capacidades redutoras de atrito, como é o caso de ensaios realizados com óleos base (livres de aditivos), o coeficiente de atrito não depende da rugosidade e da direção de acabamento. Nos ensaios lubrificados com óleos usado, encontraram-se valores de coeficiente de atrito similares aos obtidos nas condições de lubrificação com óleo livres de aditivos, devido provavelmente à redução do MoDTC no lubrificante como tem sido identificado por diferentes autores. Quando foram comparados os óleos usados contaminados com etanol com os óleos usados contaminados com gasolina, encontrou-se maior oxidação nestes últimos. Mesmo que estas diferenças de oxidação dos óleos não significaram diferenças em termos de atrito, estas podem ser importantes na medida em que óleos mais oxidados podem favorecer o desgaste oxidativo. / Smooth and rough anisotropic surfaces were used to evaluate the influence of surface roughnesss and lay direction on the in-situ formation of MoS2 from MoDTC in tribological tests. Also, this work evaluated the friction response of engine lubricants which were used in passenger cars and dynamometer tests fueled both with ethanol (E100) and gasoline (E22). It was found that both the lay direction as the surface roughness were critical for the MoDTC -MoS2 reaction. The lay direction influence due to tangential loads generate different responses when tests were conducted along and across the lay, since the latter showed higher asperities plastic deformation , which favors free oxides surfaces, which has been indicated as a condition for the sequence by MoDTC formed MoS2. For this reason the friction coefficient values related to MoS2 were obtained only for tests conducted on rough surfaces and across the lay. For surfaces with plasticity index values greater than 1 and which are not formed films with good friction-reducing capabilities, such as the tests lubricated with base oil (free aditives), the friction coefficient does not depends on the surface roughness and lay direction. For the tests conducted with used engine oils, the friction coefficient values were similar to those obtained on tests lubricated with free additives oils, this could be related by MoDTC depletion in the lubricants as have been identified by different authors. Comparing the used oils contaminated with ethanol with the used oils contaminated with gasoline, higher oxidation was founded in the latter. Even if these differences in oil oxidation not meant differences friction, these may be important as more oxidesed oils can promote oxidative wear.

O principal objetivo deste trabalho foi estudar a influência do tratamento superficial com laser de femtossegundo em amostras de alumina e compósito de alumina-zircônia estabilizada com ítria para depósito e aderência de apatita. Os resultados obtidos mostraram que houve a formação de apatita sobre as superfícies das amostras que foram texturizadas com laser de femtossegundo e em seguida imersa em 1,5 SBF. Este método biomimético pôde, por conseguinte, tornar estas cerâmicas bioativas. Também houve a formação de apatita na superfície das amostras sem o tratamento a laser. Os efeitos da texturização na superfície para as diferentes cerâmicas e a influência do tempo de imersão em 1,5 SBF são discutidos, a fim de determinar a condição ótima para estimular a deposição e a adesão da apatita na superfície dos materiais. Finalmente, os resultados obtidos das diferentes análises são comparados. A adesão da hidroxiapatita é essencial para interação com o substrato e depende das propriedades das superfícies dos materiais. A qualidade desta adesão influenciará sua morfologia e a capacidade futura de osseointegração. As características de superfície dependem da química de superfície, energia de superfície e topografia de superfície. Geralmente, a reatividade de superfície e energia de superfície pode ser influenciada pelas características de molhabilidade, influenciando o desempenho de biomateriais. A adesão e crescimento da apatita depositada também é função da rugosidade superficial. O tratamento superficial com laser de femtossegundo melhora consideravelmente a adesão da apatita obtida pelo recobrimento biomimético nas superfícies dos materiais. / The main objective of this work was to study the influence of femtosecond laser surface treatment on samples of alumina and composite of zirconia-alumina yttria stabilized for deposit and adhesion of apatite. The results showed that there was apatite formation on the surfaces of the samples that have been textured with femtosecond laser and then immersed in SBF 1.5. This biomimetic method can therefore make these bioactive ceramics. There was also the formation of apatite in the samples without laser treatment. The effects of texturing surface for the different ceramics and the influence of immersion time in SBF 1.5 are discussed in order to determine the optimal conditions to promote the deposition and the adhesion of the apatite in the material`s surface. Finally, the results of the different analyzes are compared. The adhesion of hydroxyapatite is essential for interaction with the substrate and depends on the properties of material´s surface. The quality of this adhesion will influence their morphology and the future ability of osseointegration. The surface characteristics depend on the surface chemical, surface energy and surface topography. Generally, the reactivity of surface and the energy of surface can be affected by wetting characteristics influencing the performance of biomaterials. The adhesion and growth of apatite deposited is also a function of surface roughness. The femtosecond laser surface treatment greatly improves the adhesion of apatite obtained by biomimetic coating on the surfaces of materials.

O principal objetivo deste trabalho foi estudar a influência do tratamento superficial com laser de femtossegundo em amostras de alumina e compósito de alumina-zircônia estabilizada com ítria para depósito e aderência de apatita. Os resultados obtidos mostraram que houve a formação de apatita sobre as superfícies das amostras que foram texturizadas com laser de femtossegundo e em seguida imersa em 1,5 SBF. Este método biomimético pôde, por conseguinte, tornar estas cerâmicas bioativas. Também houve a formação de apatita na superfície das amostras sem o tratamento a laser. Os efeitos da texturização na superfície para as diferentes cerâmicas e a influência do tempo de imersão em 1,5 SBF são discutidos, a fim de determinar a condição ótima para estimular a deposição e a adesão da apatita na superfície dos materiais. Finalmente, os resultados obtidos das diferentes análises são comparados. A adesão da hidroxiapatita é essencial para interação com o substrato e depende das propriedades das superfícies dos materiais. A qualidade desta adesão influenciará sua morfologia e a capacidade futura de osseointegração. As características de superfície dependem da química de superfície, energia de superfície e topografia de superfície. Geralmente, a reatividade de superfície e energia de superfície pode ser influenciada pelas características de molhabilidade, influenciando o desempenho de biomateriais. A adesão e crescimento da apatita depositada também é função da rugosidade superficial. O tratamento superficial com laser de femtossegundo melhora consideravelmente a adesão da apatita obtida pelo recobrimento biomimético nas superfícies dos materiais. / The main objective of this work was to study the influence of femtosecond laser surface treatment on samples of alumina and composite of zirconia-alumina yttria stabilized for deposit and adhesion of apatite. The results showed that there was apatite formation on the surfaces of the samples that have been textured with femtosecond laser and then immersed in SBF 1.5. This biomimetic method can therefore make these bioactive ceramics. There was also the formation of apatite in the samples without laser treatment. The effects of texturing surface for the different ceramics and the influence of immersion time in SBF 1.5 are discussed in order to determine the optimal conditions to promote the deposition and the adhesion of the apatite in the material`s surface. Finally, the results of the different analyzes are compared. The adhesion of hydroxyapatite is essential for interaction with the substrate and depends on the properties of material´s surface. The quality of this adhesion will influence their morphology and the future ability of osseointegration. The surface characteristics depend on the surface chemical, surface energy and surface topography. Generally, the reactivity of surface and the energy of surface can be affected by wetting characteristics influencing the performance of biomaterials. The adhesion and growth of apatite deposited is also a function of surface roughness. The femtosecond laser surface treatment greatly improves the adhesion of apatite obtained by biomimetic coating on the surfaces of materials.

Superfícies anisotrópicas lisas e rugosas foram usadas para avaliar o efeito da rugosidade e da direção de acabamento na formação de MoS2 a partir de MoDTC em ensaios tribologicos lubrificados com óleos de motor completamente formulados. Igualmente foi avaliada a resposta de atrito de lubrificantes de motor usados em carros de passageiros e em testes de dinamômetro abastecidos com etanol (E100) e gasolina (E22). Encontrou-se que tanto a direção de acabamento quanto a rugosidade foram fundamentais na reação MoDTC - MoS2. A direção de acabamento influenciou na medida que carregamentos tangenciais geram respostas diferentes nos ensaios quando são realizados paralelos e perpendiculares às linhas de acabamento, dado que para os últimos apresenta-se maior deformação plástica das asperezas, o qual favorece a obtenção de superfícies livres de óxidos, que tem sido indicada como uma condição necessário para que aconteça a reação MoDTC - MoS2. Por esta razão os valores de coeficiente de atrito próprios da formação de MoS2 foram obtidos somente nas superfícies rugosas ensaiadas perpendiculares às marcas de acabamento. Para superfícies com valores de índice de plasticidade superiores a 1 e nos quais não são formados filmes com boas capacidades redutoras de atrito, como é o caso de ensaios realizados com óleos base (livres de aditivos), o coeficiente de atrito não depende da rugosidade e da direção de acabamento. Nos ensaios lubrificados com óleos usado, encontraram-se valores de coeficiente de atrito similares aos obtidos nas condições de lubrificação com óleo livres de aditivos, devido provavelmente à redução do MoDTC no lubrificante como tem sido identificado por diferentes autores. Quando foram comparados os óleos usados contaminados com etanol com os óleos usados contaminados com gasolina, encontrou-se maior oxidação nestes últimos. Mesmo que estas diferenças de oxidação dos óleos não significaram diferenças em termos de atrito, estas podem ser importantes na medida em que óleos mais oxidados podem favorecer o desgaste oxidativo. / Smooth and rough anisotropic surfaces were used to evaluate the influence of surface roughnesss and lay direction on the in-situ formation of MoS2 from MoDTC in tribological tests. Also, this work evaluated the friction response of engine lubricants which were used in passenger cars and dynamometer tests fueled both with ethanol (E100) and gasoline (E22). It was found that both the lay direction as the surface roughness were critical for the MoDTC -MoS2 reaction. The lay direction influence due to tangential loads generate different responses when tests were conducted along and across the lay, since the latter showed higher asperities plastic deformation , which favors free oxides surfaces, which has been indicated as a condition for the sequence by MoDTC formed MoS2. For this reason the friction coefficient values related to MoS2 were obtained only for tests conducted on rough surfaces and across the lay. For surfaces with plasticity index values greater than 1 and which are not formed films with good friction-reducing capabilities, such as the tests lubricated with base oil (free aditives), the friction coefficient does not depends on the surface roughness and lay direction. For the tests conducted with used engine oils, the friction coefficient values were similar to those obtained on tests lubricated with free additives oils, this could be related by MoDTC depletion in the lubricants as have been identified by different authors. Comparing the used oils contaminated with ethanol with the used oils contaminated with gasoline, higher oxidation was founded in the latter. Even if these differences in oil oxidation not meant differences friction, these may be important as more oxidesed oils can promote oxidative wear.

The aim of this diploma thesis is to describe mechanisms involved in a lubricant film formation in textured conformal contacts. For exploring of the lubricant film formation, the method of optical interferometry is implemented on a pin-on-disc tribometer. That allows to study an influence of a texture on lubricant film thickness and coefficient of friction of textured samples. These samples have different parameters of a texture. On the basis of these effects and the visual image of the contact, the flow of lubricant in the contact area is described. Shallow dimples lead to larger film thickness in elasto-hydrodynamic lubrication regime. They act like a lubricant reservoir. Deep dimples positively affect film thickness in hydrodynamic lubrication regime, where the effect of shallow dimples descend. During experiments, the formation of a cavitation is observed. The cavitation causes a starvation of dimples in many cases. This leads to reducing of the lubricant film thickness. This effect can be eliminated by appropriate parameters of texture in operational conditions of elements.

The aim of this diploma thesis is to experimentally elucidate the connection between the friction of the specimen with the textured surface and the optical observation of the sliding contact surface. The thesis focuses on the configuration of the journal bearing. This configuration is achieved by replacing the block with a circular sapphire section on a block-on-ring tribometer. For exploring of the lubricant film formation, the method of optical interferometry and fluorescence is implemented on the block-on-ring tribometer. These adjustments allow examination of the effect of the textured surface on the friction coefficient and the thickness of the lubricant film. In a mixed mode, the textures cause a significant increase in friction values and reduce the thickness of the lubricant film. The negative influence of dimples increases with the increasing radial load size. In the hydrodynamic mode, the textures have a lower negative effect on the resulting values than in the mixed mode. The changes are dependent on the size of the radial load and the viscosity of the lubricant. In the hydrodynamic mode, cavitation was not observed, and the effect of the textured surface does not correspond to theoretical prerequisites, which is reflected by lower lubricant thickness and higher friction.

Diploma thesis describes influence of directed modificated topography of frictional surfaces on fatigue wear non-conformal incurvate solids. It was created 3D parametric model of experimental test rig in modelling environment Autodesk Inventor. With the help of model was designed and carried reconstruction of experimental test rig so to possible obtain repeatable results under the sliding conditions of frictional surfaces. It enabled show influence of surface iregularities (dents) frictional surfaces on contact fatigue service life in conditions mixed lubrication regime and different values of slide to roll ratio.

Diploma thesis describes analysis of influence of surface texturing on non-conformal rubbing surfaces. High speed camera was used to observe the effect of micro-dents of various depths on film thickness under pure rolling and rolling/sliding conditions. It can be concluded from the obtained results that micro-texture of suitable sizes can results in film thickness increase without lubrication film breakdown.