Made available in DSpace on 2014-06-11T19:28:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-11Bitstream added on 2014-06-13T20:58:35Z : No. of bitstreams: 1 mazur_rl_me_guara.pdf: 2192483 bytes, checksum: 24772053abc0675fdf4455448fe4adc3 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / As superligas à base de níquel são aplicadas nos mais diversos e complexos sistemas de engenharia, entretanto há poucos dados sobre o comportamento erosivo destas superligas frente ao impacto de particulas sólidas em um fluxo gasoso. A erosão por partícula sólida é um fenômeno complexo e caracteriza-se pela deformação e remoção de material durante o impacto das partículas, gerando elevadas temperaturas. As superligas à base de níquel Nimonic 80 A e Inconel 600, são materiais que possuem ótimas propriedades mecânicas emelevadas temperaturas, por este motivo, as suas características quanto à erosão em temperatura ambiente, serão medidas e analisadas, em vista da perda das propriedades mecânicas dos aços em temperaturas mais altas durante o impacto das partículas. Os ensaios de erosão foram realizados em um dispositivo do tipo jato de impacto ar-areia, onde as partículas erosivas forma introduzidas em um sistema à alta pressão e aceleradas ao longo de um bocal antes de impactar a superfície do material, permitindo simular os principais parâmetros do desgaste erosivo. Os ensaios realizados apresentaram pequenas diferenças para todosângulos de impacto testados (15°, 30°, 60°, 90°), porém os intervalos de confiança se superpõem para quase todos eles apesar da marcante diferença entre as propriedades mecânicas das superligas Nimonic 80 A e Inconel 600, não sendo possível estabelecer alguma correlação com a resistência à erosâo. / The Ni-base superalloys are applied in several and complexest engineering systems, however there are few data about the erosive behaviour of these superalloys regarding the impact of solid particles in a gaseous flow. The solid particle erosion is a complex phenomenon and it is characerized by the deformation and material removal during the impact of the particles generating high temperatures. The Ni-basesuperalloys Nimonic 80 A and Inconel 600, have excellent mechanical properties in high temperature, by this reason, theirs characteristics in erosion at room temperature, will be measured and analyzed, in view of the losses of the mechanical properties of the steels in higher temperatures during the impact of the particles. The erosion tests have been performed in air-sand jet impingement device, where the erosive particles were introduced in a system with high pressure and accelerated along a nozzle before impact the surface of the material, allowing to simulate the main parameters of the erosion wear. The results showed small differences for all impact angles tested (15°, 30°, 60°, 90°), however the reliable intervals have been superimpsed for almost all of them, in spite of the great differences among the mechanical properties of the superalloys Nimonic 80 A and Inconel 600, it was noto possible to establish some correlation with the erosion resistance.

No description available.

Orientador: Sérgio João Crnkovic / Resumo: As superligas à base de níquel são aplicadas nos mais diversos e complexos sistemas de engenharia, entretanto há poucos dados sobre o comportamento erosivo destas superligas frente ao impacto de particulas sólidas em um fluxo gasoso. A erosão por partícula sólida é um fenômeno complexo e caracteriza-se pela deformação e remoção de material durante o impacto das partículas, gerando elevadas temperaturas. As superligas à base de níquel "Nimonic 80 A" e Inconel 600", são materiais que possuem ótimas propriedades mecânicas emelevadas temperaturas, por este motivo, as suas características quanto à erosão em temperatura ambiente, serão medidas e analisadas, em vista da perda das propriedades mecânicas dos aços em temperaturas mais altas durante o impacto das partículas. Os ensaios de erosão foram realizados em um dispositivo do tipo jato de impacto ar-areia, onde as partículas erosivas forma introduzidas em um sistema à alta pressão e aceleradas ao longo de um bocal antes de impactar a superfície do material, permitindo simular os principais parâmetros do desgaste erosivo. Os ensaios realizados apresentaram pequenas diferenças para todosângulos de impacto testados (15°, 30°, 60°, 90°), porém os intervalos de confiança se superpõem para quase todos eles apesar da marcante diferença entre as propriedades mecânicas das superligas "Nimonic 80 A" e Inconel 600", não sendo possível estabelecer alguma correlação com a resistência à erosâo. / Abstract: The Ni-base superalloys are applied in several and complexest engineering systems, however there are few data about the erosive behaviour of these superalloys regarding the impact of solid particles in a gaseous flow. The solid particle erosion is a complex phenomenon and it is characerized by the deformation and material removal during the impact of the particles generating high temperatures. The Ni-basesuperalloys "Nimonic 80 A" and Inconel 600", have excellent mechanical properties in high temperature, by this reason, theirs characteristics in erosion at room temperature, will be measured and analyzed, in view of the losses of the mechanical properties of the steels in higher temperatures during the impact of the particles. The erosion tests have been performed in air-sand jet impingement device, where the erosive particles were introduced in a system with high pressure and accelerated along a nozzle before impact the surface of the material, allowing to simulate the main parameters of the erosion wear. The results showed small differences for all impact angles tested (15°, 30°, 60°, 90°), however the reliable intervals have been superimpsed for almost all of them, in spite of the great differences among the mechanical properties of the superalloys "Nimonic 80 A" and "Inconel 600", it was noto possible to establish some correlation with the erosion resistance. / Mestre

Centrifugal separation is a crucial piece of technology, used in a wide range of industries. In cases where solid particles are included in the working medium, erosive wear of componentsinside a centrifugal separator is one of the reasons limiting its service life. In the present work, erosion of some candidate materials of metals, hard metals and polymers were tested to represent the erosive conditions inside a centrifugal separator, and to study the erosion behavior between different material groups. A literature study was conducted to give an overview of the field of erosion, and to evaluate which erosion parameters to consider for testing. A centrifugal erosion test rig was used for the testing, using natural sand, sieved to a size interval of 500 to 700 µm, as erodent, at both 90° and 30° impact angle. Every material was tested at 100 m/s impact velocity, while only metals and polymers were tested at 70 m/s. The erosion rates, volumes of material removed per mass of impinging erodent, were measured and used to rank the candidate materials within each respective material group. Surface analysis of the eroded surfaces were conducted, using SEM, to determine the mechanism of material removal. Relation between erosion resistance, erosion mechanism and material property were investigated.

No description available.

Thermal Barrier Coating systems (TBCs) serve as a key component in gas turbines in aerospace engines, isolating the metallic substrate from severe heat flux of the environment. The durability of TBCs has been considered to be a critical issue to determine the service lifespan of hot section components. Comprehensive studies of failure mechanisms benefit the gas turbine industry to develop TBCs with better material properties and stable microstructures, thus potentially enhancing their durability. To date, many failure mechanism analyses have been conducted based on the understanding of critical residual stress developed under different thermal tests. For the present study, using the Finite Element (FE) method with temperature-process-dependent model parameters, the maximum residual stress is calculated with evolution of the localized/global interfacial roughness profile based on Electron Beam-Physical Vapour Deposition Thermal Barrier Coating system (EB-PVD TBCs). With studies of cracking routes from past research, qualitative failure mechanism analysis is conducted for EB-PVD TBCs. In addition, the estimated energy release rates are compared to reveal the effect of different thermal profiles on the crack driving forces for Atmospheric Plasma Sprayed Thermal Barrier Coating systems (APS-TBCs). Using previously observed cracking routes from different thermal cycling experiments, a quantitative failure mechanism analysis is conducted for APS-TBCs with modified analytical expressions. In addition, literature works revealed that physics and mechanics-based models were proposed to evaluate environment induced damage. For the last part of my research, erosion of EB-PVD TBCs is estimated using a modified solid particle erosion model. A stochastic approach is applied to study the erosion of EB-PVD topcoat (TC) under real engine service conditions. The durability of TBCs is affected by both oxidation-induced degradation and environment-induced damage. The combination of “internal” crack driving forces (generated from residual stresses developed upon different stages of thermal cycles) and “external” erosion damage (from temperature-process dependent brittle/ductile erosion) lead to complexity of evaluating durability under different service conditions.

Triebwerkskomponenten in Luft- und Raumfahrtfahrzeugen unterliegen im Einsatz erosivem Verschleiß. Feine Stäube und Partikel wie Sand, Vulkanasche und Eiskristalle führen bei einer Wechselwirkung mit den Triebwerksschaufeln zum Materialabtrag. Auswirkungen reichen von einer erhöhten Oberflächenrauheit der Schaufel bis hin zu einer Veränderung der Bauteilgeometrie. Im Bereich des Verdichters treffen z. B. angesaugte Partikel senkrecht auf die Schaufelvorderkanten auf, wodurch sich die Profilsehnen verkürzen. Im Bereich der Schaufelhinterkanten erfolgt aufgrund des flachen Auftreffwinkels des Abrasivmittels ein flächiger Materialabtrag, der die Schaufeldicke reduziert. Durch eine Beschichtung von Bauteiloberflächen eröffnet sich eine Möglichkeit, Triebwerksschaufeln effektiv vor Partikelerosion zu schützen. Im Vordergrund der Entwicklung von Erosionsschutzschichten steht ihre verschleißreduzierende Wirkung, die durch das bestmögliche Verhältnis von Schichtzähigkeit und –härte zum Grundwerkstoff erreicht wird. Diese Arbeit liefert Untersuchungen zu Wechselwirkungen zwischen Beschichtungen und Grundwerkstoff als Gesamtsystem und den daraus resultierenden Einfluss auf das Partikelerosionsverhalten des Bauteils. Ziel der Untersuchungen ist es, eine bestmögliche Auswahl qualifizierter Schichtsysteme für den Erosionsschutz zu gewährleisten. Dafür wurden verschiedene Kombinationen aus PVD-Beschichtungen (konventionelle Hartstoffschichten, Cr2AlC MAX-Phase, DLC ta-C) und Grundwerkstoffen (Inconel 718 lösungsgeglüht, Inconel 718 ausscheidungsgehärtet, WC-Co) hinsichtlich ihres Partikelerosionsverhaltens getestet und ihre Schichtverbundeigenschaften charakterisiert, um relevante Einflussgrößen auf die Partikelerosion zu eruieren. Die dabei ablaufenden verschiedenen Erosionsmechanismen wurden analysiert und in grundlegende Modelle überführt. Abgerundet wurden diese experimentellen Untersuchungen mit theoretischen Betrachtungen zum mechanischen Verhalten unterschiedlicher Kombinationen von Beschichtung und Grundwerkstoff bei Partikelimpakt. Die vorliegende Arbeit leistet einen essentiellen Beitrag zum besseren Verständnis des Einflusses von Schicht-Grundwerkstoff-Verbundeigenschaften auf das Partikelerosionsverhalten. Die Ergebnisse zeigen deutlich, dass das Deformationsverhalten des Substrats einen erheblichen Einfluss auf das Erosionsverhalten des Schicht-Grundwerkstoff-Systems hat. Im Falle eines duktilen Substrats ist eine entsprechend gute Schichthaftung von wesentlicher Bedeutung. Die Erosionsversuche auf hartem WCCo Grundwerkstoff zeigen, dass bei Vorhandensein identischer mechanischer Eigenschaften von Substrat und Beschichtung die Schichthaftung nicht in dem Maße erforderlich ist, wie bei plastisch verformbaren Grundwerkstoffen. Erstmalig wird in dieser Arbeit das schadenstolerante Erosionsverhalten der superharten DLC ta-C-Beschichtung auf duktilem Inconel 718 aufgezeigt. Der hohe elastische Verformungsanteil der DLC-Beschichtung in Kombination mit einer guten Schichthaftung resultiert in einem hohen Erosionswiderstand des Schicht-Grundwerkstoff-Verbunds, wobei im Versuch keine plastische Verformung des Grundwerkstoffs nachgewiesen wird.

No description available.