Orientador: Vicente Afonso Ventrella / Resumo: A evolução do processo de furação nos trouxe ao desenvolvimento do método de furação por laser pulsado, mas não temos definido o que a variação de cada parâmetro produz nos microfuros em relação à qualidade dos mesmos medidos com base em seu formato em aço inoxidável austenítico AISI 316L. O presente estudo analisou como variações na potência de pico, largura temporal do pulso e existência ou não de atmosfera protetora podem mudar os tamanhos, formatos e profundidades em microfuros. Produziram-se combinações dos parâmetros que foram usadas para obter furos em chapas de aço AISI 316L com 1 mm de espessura com o uso de uma fonte de laser pulsado Nd:YAG e analisar as propriedades em cada combinação, tais como diâmetros de entrada e de saída, profundidades e formatos observados em estereoscópio. / Mestre

The imminent emergence of the hydrogen fuel industry has resulted in an urgent mandate for very specific material testing. Although storage of pressurized hydrogen gas is both practical and attainable, demands for increasing storage pressures (currently around 70 MPa) continue to present unexpected material compatibility issues. It is imperative that materials commonly used in gaseous hydrogen service are properly tested for hydrogen embrittlement resistance. To assess material behavior in a pressurized hydrogen environment, procedures were designed to test materials for susceptibility to hydrogen embrittlement. Of particular interest to the field of high-pressure hydrogen in the automotive industry, austenitic stainless steels SUS 316 and 316L were used to validate the test programs. Tests were first performed in 25 MPa helium and hydrogen at room temperature and at -40°C. Tests in a 25 MPa hydrogen atmosphere caused embrittlement in SUS 316, but not in 316L. This indicated that alloys with higher stacking fault energies (316L) are more resistant to hydrogen embrittlement. Decreasing the test temperature caused slight embrittlement in 316L and significantly enhanced it in 316. Alternatively, a second set of specimens was immersed in 70 MPa hydrogen at 100°C until reaching a uniform concentration of absorbed hydrogen. Specimens were then loaded in tension to failure to determine if a bulk saturation of hydrogen provided a similar embrittling effect. Neither material succumbed to the effects of gaseous pre-charging, indicating that the embrittling mechanism requires a constant supply of hydrogen at the material surface rather than having bulk concentration of dissolved hydrogen. Permeation tests were also performed to ensure that hydrogen penetrated the samples and to develop material specific permeation constants. To pave the way for future work, prototype equipment was constructed allowing tensile or fatigue tests to be performed at much higher hydrogen pressures. To determine the effect of pressure on hydrogen embrittlement, additional tests can be performed in hydrogen pressures up to 85 MPa hydrogen. The equipment will also allow for cyclic loading of notched tensile or compact tension specimens for fatigue studies.

The imminent emergence of the hydrogen fuel industry has resulted in an urgent mandate for very specific material testing. Although storage of pressurized hydrogen gas is both practical and attainable, demands for increasing storage pressures (currently around 70 MPa) continue to present unexpected material compatibility issues. It is imperative that materials commonly used in gaseous hydrogen service are properly tested for hydrogen embrittlement resistance. To assess material behavior in a pressurized hydrogen environment, procedures were designed to test materials for susceptibility to hydrogen embrittlement. Of particular interest to the field of high-pressure hydrogen in the automotive industry, austenitic stainless steels SUS 316 and 316L were used to validate the test programs. Tests were first performed in 25 MPa helium and hydrogen at room temperature and at -40°C. Tests in a 25 MPa hydrogen atmosphere caused embrittlement in SUS 316, but not in 316L. This indicated that alloys with higher stacking fault energies (316L) are more resistant to hydrogen embrittlement. Decreasing the test temperature caused slight embrittlement in 316L and significantly enhanced it in 316. Alternatively, a second set of specimens was immersed in 70 MPa hydrogen at 100°C until reaching a uniform concentration of absorbed hydrogen. Specimens were then loaded in tension to failure to determine if a bulk saturation of hydrogen provided a similar embrittling effect. Neither material succumbed to the effects of gaseous pre-charging, indicating that the embrittling mechanism requires a constant supply of hydrogen at the material surface rather than having bulk concentration of dissolved hydrogen. Permeation tests were also performed to ensure that hydrogen penetrated the samples and to develop material specific permeation constants. To pave the way for future work, prototype equipment was constructed allowing tensile or fatigue tests to be performed at much higher hydrogen pressures. To determine the effect of pressure on hydrogen embrittlement, additional tests can be performed in hydrogen pressures up to 85 MPa hydrogen. The equipment will also allow for cyclic loading of notched tensile or compact tension specimens for fatigue studies.

Orientador: Vicente Afonso Ventrella / Resumo: O aço inoxidável austenítico 316L é um material empregado nas indústrias que requerem resistência à corrosão e mecânica como a indústria de petróleo, gás natural e papel e celulose. O uso do laser vem se tornando uma ferramenta atrativa em relação as soldagens convencionais, devido aos seus benefícios que vão desde processo sem contato, controle de energia do feixe e fácil automatização do sistema. Nesse trabalho o objetivo foi analisar a influência do processo de soldagem laser pulsado Nd: YAG nas características mecânicas e microestruturais da junta soldada de chapas de aço inoxidável austenítico AISI 316L com 1,0 mm de espessura, averiguando o efeito da energia de soldagem nas características do cordão de solda desenvolvidas no Laboratório de Soldagem Laser, do Departamento de Engenharia Mecânica da FEIS UNESP. Foram realizadas soldagens de juntas de chapas aço inoxidável austenítico com valores fixos de energias de soldagem em 8 Joules, largura temporal em 4 ms, velocidade de soldagem em 1 mm/s, variando apenas a frequência entre 2 e 10 Hz, com isso obteve-se diferentes taxas de sobreposição, com proteção gasosa de argônio. Com as diferentes condições obtidas foram realizadas análises macrográficas das juntas soldadas, através de secções transversais das mesmas e, ensaios de microdureza Vickers e ensaios de tração. Os resultados obtidos mostraram que o cordão de solda se comportou de forma frágil, rompendo-se todos no cordão, a fractografia da seção transversal aparentem... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre

The contamination of 316L stainless steel surfaces within an electrospray ionisation source of a mass spectrometer is investigated. An accelerated method of contamination is used. Following initial test method development and investigation of the contamination resulting on the ion transfer components (sample cone, outer cone and extraction cone), flat samples are employed within the ionisation source. This enables characterisation of the contamination composition, morphology and build-up with time. Blood plasma is introduced into the mass spectrometer as it is a widely analysed substance that is known to result in contamination. The contamination from a mixture of human blood plasma, diluted in methanol, and a water/acetonitrile mobile phase is found to contain inorganic NaCl crystals embedded in a matrix of organic residues. The morphology shows self-organising features as the contamination builds. A model is proposed to explain the morphology, involving rapid evaporation of the droplets that impinge on the stainless steel surface. Two types of surface modification are considered for the stainless steel: electrochemically grown films and coatings deposited by vapour deposition. A method for electrochemical film growth is developed, enabling nanoporous films to be formed on the stainless steel in 5 M sulphuric acid at 60°C by square wave pulse polarisation between active or transpassive and passive potentials. The films are characterised using glow discharge optical emission spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, Rutherford backscattering spectroscopy and nuclear reaction analysis. The films are shown to be chromium- and molybdenum-rich relative to the substrate, and to consist mainly of sulphates, oxides and hydroxides. The morphology and composition of the films are discussed in relation to the polarisation conditions and mechanism of film formation. A range of vapour deposited coatings are considered: TiN, TiC, TiB2, Graphit-iC, and diamond-like carbon coatings with Si and N2 dopants and with varying sp2:sp3 ratios. In addition, a hydrophobic coating is deposited on the stainless steel by immersion, in order to provide a significant variation in surface energy. Surface analysis of the coatings is carried out, considering their sp2:sp3 ratios, their electrical conductivities, their water contact angle, and the various components of the surface energy. The contamination build-up on the surface of uncoated 316L stainless steel is compared with that on stainless steel with the various surface modifications. A method for quantification of the build-up of contamination on flat samples is developed using white light interferometry. The surface modifications which result in the slowest contamination build-up with time are then applied to the ion transfer components of the mass spectrometer. The robustness of the mass spectrometric response for the selected coated surfaces is compared with that of the uncoated stainless steel. The electrochemically grown films and two of the doped diamond-like carbon coatings are found to be successful in reducing the build-up of contamination.

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Submitted by DAIR FERREIRA SALGADO JUNIOR null (dairsalgado@gmail.com) on 2017-01-05T17:54:35Z No. of bitstreams: 1 Dissertação.pdf: 5078960 bytes, checksum: f66841a9969c704bd527a1761f8e7e3b (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2017-01-10T17:08:35Z (GMT) No. of bitstreams: 1 salgadojunior_df_me_ilha.pdf: 5078960 bytes, checksum: f66841a9969c704bd527a1761f8e7e3b (MD5) / Made available in DSpace on 2017-01-10T17:08:35Z (GMT). No. of bitstreams: 1 salgadojunior_df_me_ilha.pdf: 5078960 bytes, checksum: f66841a9969c704bd527a1761f8e7e3b (MD5) Previous issue date: 2016-12-12 / A evolução do processo de furação nos trouxe ao desenvolvimento do método de furação por laser pulsado, mas não temos definido o que a variação de cada parâmetro produz nos microfuros em relação à qualidade dos mesmos medidos com base em seu formato em aço inoxidável austenítico AISI 316L. O presente estudo analisou como variações na potência de pico, largura temporal do pulso e existência ou não de atmosfera protetora podem mudar os tamanhos, formatos e profundidades em microfuros. Produziram-se combinações dos parâmetros que foram usadas para obter furos em chapas de aço AISI 316L com 1 mm de espessura com o uso de uma fonte de laser pulsado Nd:YAG e analisar as propriedades em cada combinação, tais como diâmetros de entrada e de saída, profundidades e formatos observados em estereoscópio.

Submitted by CAROLINA DE OLIVEIRA SILVA null (caroli_oliveira@hotmail.com) on 2017-04-18T05:45:14Z No. of bitstreams: 1 trabalho revisado - Carol corrigida 18-04.pdf: 4289233 bytes, checksum: 352f0db50ce2a9d93581a7a0dd27df20 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-04-18T18:52:43Z (GMT) No. of bitstreams: 1 silva_co_me_ilha.pdf: 4289233 bytes, checksum: 352f0db50ce2a9d93581a7a0dd27df20 (MD5) / Made available in DSpace on 2017-04-18T18:52:43Z (GMT). No. of bitstreams: 1 silva_co_me_ilha.pdf: 4289233 bytes, checksum: 352f0db50ce2a9d93581a7a0dd27df20 (MD5) Previous issue date: 2017-02-17 / O aço inoxidável austenítico 316L é um material empregado nas indústrias que requerem resistência à corrosão e mecânica como a indústria de petróleo, gás natural e papel e celulose. O uso do laser vem se tornando uma ferramenta atrativa em relação as soldagens convencionais, devido aos seus benefícios que vão desde processo sem contato, controle de energia do feixe e fácil automatização do sistema. Nesse trabalho o objetivo foi analisar a influência do processo de soldagem laser pulsado Nd: YAG nas características mecânicas e microestruturais da junta soldada de chapas de aço inoxidável austenítico AISI 316L com 1,0 mm de espessura, averiguando o efeito da energia de soldagem nas características do cordão de solda desenvolvidas no Laboratório de Soldagem Laser, do Departamento de Engenharia Mecânica da FEIS UNESP. Foram realizadas soldagens de juntas de chapas aço inoxidável austenítico com valores fixos de energias de soldagem em 8 Joules, largura temporal em 4 ms, velocidade de soldagem em 1 mm/s, variando apenas a frequência entre 2 e 10 Hz, com isso obteve-se diferentes taxas de sobreposição, com proteção gasosa de argônio. Com as diferentes condições obtidas foram realizadas análises macrográficas das juntas soldadas, através de secções transversais das mesmas e, ensaios de microdureza Vickers e ensaios de tração. Os resultados obtidos mostraram que o cordão de solda se comportou de forma frágil, rompendo-se todos no cordão, a fractografia da seção transversal aparentemente apresentou muitos vazios, a ZTA mostrou-se muito pequena e aparentemente não houve crescimento do grão, o aumento da sobreposição da junta soldada tem influencia direta com a dureza do material. / 316L austenitic stainless steel is a material used in industries which require mechanical and corrosion resistance like the petroleum industry, natural gas and paper/cellulose industry. The usage of laser has become an attractive tool compared to conventional welding, due to its benefits ranging from contactless process, beam power control and easy system automation. In this work the objective was to analyze the influence of the Nd: YAG pulsed laser welding process on the mechanical and microstructural characteristics of the welded joint of AISI 316L austenitic stainless steel sheets with 1.0 mm thickness, investigating the effect of the welding energy on the characteristics Of the weld bead developed at the Laser Welding Laboratory of the Mechanical Engineering Department of FEIS UNESP. Sheet joints of austenitic stainless steel were welded with fixed values of welding energies in 8 Joules, temporal width in 4 ms, welding speed in 1 mm / s, only varying the frequency between 2 to 10 Hz. With this, different rates of overlap, with argon gas protection. With the different conditions obtained, macroscopic analysis of the welded joints were carried out through cross sections of the welds and Vickers microhardness tests and tensile tests. The results showed that the weld bead behaved in a fragile manner, breaking all in the cord, the fracture of the cross section apparently presented many voids, the ZTA showed to be very small and apparently there was no growth in the grain, the increase of the overlap of the welded joint has a direct influence on the hardness of the material.

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The imminent emergence of the hydrogen fuel industry has resulted in an urgent mandate for very specific material testing. Although storage of pressurized hydrogen gas is both practical and attainable, demands for increasing storage pressures (currently around 70 MPa) continue to present unexpected material compatibility issues. It is imperative that materials commonly used in gaseous hydrogen service are properly tested for hydrogen embrittlement resistance. To assess material behavior in a pressurized hydrogen environment, procedures were designed to test materials for susceptibility to hydrogen embrittlement. Of particular interest to the field of high-pressure hydrogen in the automotive industry, austenitic stainless steels SUS 316 and 316L were used to validate the test programs. Tests were first performed in 25 MPa helium and hydrogen at room temperature and at -40°C. Tests in a 25 MPa hydrogen atmosphere caused embrittlement in SUS 316, but not in 316L. This indicated that alloys with higher stacking fault energies (316L) are more resistant to hydrogen embrittlement. Decreasing the test temperature caused slight embrittlement in 316L and significantly enhanced it in 316. Alternatively, a second set of specimens was immersed in 70 MPa hydrogen at 100°C until reaching a uniform concentration of absorbed hydrogen. Specimens were then loaded in tension to failure to determine if a bulk saturation of hydrogen provided a similar embrittling effect. Neither material succumbed to the effects of gaseous pre-charging, indicating that the embrittling mechanism requires a constant supply of hydrogen at the material surface rather than having bulk concentration of dissolved hydrogen. Permeation tests were also performed to ensure that hydrogen penetrated the samples and to develop material specific permeation constants. To pave the way for future work, prototype equipment was constructed allowing tensile or fatigue tests to be performed at much higher hydrogen pressures. To determine the effect of pressure on hydrogen embrittlement, additional tests can be performed in hydrogen pressures up to 85 MPa hydrogen. The equipment will also allow for cyclic loading of notched tensile or compact tension specimens for fatigue studies. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate