The rolling-sliding dry-wear behaviour of a series of bainitic steels and a standard pearlitic rail steel have been compared over a range of contact stress and creepage conditions applicable to the British Rail network. A rolling-sliding wear machine has been constructed - LEROS - which allows very high contact stresses to be combined with high creepages under well controlled conditions. Materials were tested on LEROS and on an Amsler machine. Limited vibration analyses were carried out on both machines and compared with the frequencies of disc surface periodic undulations. No direct linkage was determined. Despite better standard mechanical properties, the wear resistance of lower carbon bainitic steels was inferior to that of the pearlitic steel. A bainitic steel with the same carbon content as the pearlitic steel wore a little less, but at considerable expense to the pearlitic wheel steel counter-material in the wear couple. The wear resistance of bainitic steels depends upon the volume fraction of hard phase, such as carbide and martensite-austenite phase, for rolling-sliding as well as other types of dry wear loading. Pearlitic steel performs exceptionally well under certain rolling-sliding conditions, such as the majority seen in these tests, since the lamellar microstructure is modified so as to present a greater area fraction of carbide hard phase at the wear surface, a fraction in excess of bulk volume fraction. Recommendations are made for the dry wear applicability of the steels.

Submitted by MARCO ANTONIO BAPTISTELLA null (marco_baptistella@terra.com.br) on 2016-08-23T19:37:34Z No. of bitstreams: 1 REV 17. MARCO A. BAPTISTELLA.pdf: 11920777 bytes, checksum: ba33aea22870d52b190f07f07f6e333c (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-08-25T20:22:58Z (GMT) No. of bitstreams: 1 baptistella_ma_me_guara.pdf: 11920777 bytes, checksum: ba33aea22870d52b190f07f07f6e333c (MD5) / Made available in DSpace on 2016-08-25T20:22:58Z (GMT). No. of bitstreams: 1 baptistella_ma_me_guara.pdf: 11920777 bytes, checksum: ba33aea22870d52b190f07f07f6e333c (MD5) Previous issue date: 2016-08-04 / Atualmente, as cargas aplicadas nos eixos de vagões ferroviários têm sofrido aumento de esforços devido ao choque e tração no engate ferroviário. Neste trabalho o estudo foi realizado no engate tipo “F”, que tem maior utilização e interesse por parte da ferrovia, por se tratar de um engate rotativo e utilizado para descarregamento de vagões com os mais diversos tipos de carga. Este trabalho tem como objetivo, verificar se existem transformações da microestrutura no material do engate, e possíveis gerações de trincas, através do estudo do aço AAR M-201 Grau E, após o ensaio de partículas magnéticas, com corrente alternada através da aplicação de Prods. A faixa de amperagem variou-se de 100 a 1000 ampères e como meio de resfriamento, utilizou-se a água a temperatura ambiente e o ar forçado. A preparação foi feita partindo de um engate Tipo “F” completo, fornecido por um operador logístico, a cauda foi magnetizada por inteiro e depois separados os corpos de prova por corte de serra, refrigerado para não haver aquecimento. Para a caracterização microestrutural, utilizou-se uma preparação metalográfica de laboratório de bancada e ataque com Nital 2%, e fez-se uso de microscopia ótica convencional e microscopia eletrônica de varredura (MEV). Através da utilização da microscopia ótica e da microscopia eletrônica de varredura (MEV), pode-se verificar a microestrutura nas áreas que sofreram alterações microestruturais. Concluiu-se que o aço do engate, AAR M-201 grau E, após a magnetização por Prods de 300 a 1000 ampères, apresentou alteração microestrutural, onde observou-se uma estrutura de martensita acicular não revenida e geração de trincas, a mesma alteração microstrutural foi observada em amostras com resfriamento ao ar, porém sem a geração de trincas, em ampliações de 50 vezes foi nítido o efeito de queima provocado pelo Prods no material, bem como sua extensão, evidenciando áreas centrais de atuação do Prods, zonas de transição e áreas não afetadas. As trincas tiveram comportamento de propagação intergranular, para ampliações de 9300 vezes em MEV, pode-se observar que as mesmas se propagaram somente nas áreas com martensita e contornaram as áreas com maior presença da fase ferrítica. / Currently, the applied loads on the axles of railway cars has been increasing efforts due to shock and traction in railway coupling. In this work, the study was performed on the coupling type "F", which has increased use and interest on the part of the railway, because it is a rotary coupling and used for unloading of wagons with the most diverse types of cargo. This work aims, check for microstructural changes on the coupling material, and possible generation of cracks through the study of steel AAR M-201 grade and after the test of magnetic particles with alternating current by applying Prods. As amperage range, was varied from 100 to 1000 amps and as cooling medium water was used at room temperature and forced air. The preparation was made starting from a coupling type "F" full, provided by a logistics operator, the tail was magnetized in full and then separate the specimens by cutting saw, cooled to no heating. For microstructural characterization, we used a metallographic preparation of benchtop laboratory and attack Nital 2%, and was made use of conventional optical microscopy and scanning electron microscopy (SEM). By using light microscopy and scanning electron microscopy (SEM), you can check the microstructure in areas that suffered microstructural changes. It was concluded that the coupling of steel, AAR M-201 grade And after magnetization by Prods 300-1000 amps, presented change microstructural where there was a martensite acicular structure not tempered and generation of cracks, the same change microstructural was observed in air to cooling with samples, but without generating cracks at magnifications of 50 times was clear the burning effect caused by Prods in the material as well as its extension, showing the central areas of the Prods activities, transition zones and unaffected areas. The intergranular crack propagation behavior had to 9300 times magnification under SEM, it can be seen that they have spread only in areas with martensite and rounded areas with the greatest presence of the ferritic phase.