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O processo de moldagem de pós injeção é utilizado para a fabricação de peças de geometrias complexas e com alto volume de produção. Em aplicações ortodônticas e médicas, nas quais são requeridas elevadas durezas e resistências à corrosão, o aço inoxidável 17-4 PH é utilizado aplicando-se aquela técnica de conformação. A atmosfera de sinterização é responsável pelo controle das reações químicas que ocorrem durante a densificação do material e são fundamentais para a qualidade final do produto. O objetivo deste trabalho foi avaliar a influência da atmosfera de sinterização na dureza e resistência à corrosão deste tipo de aço. A remoção dos ligantes primários foi realizada por meio de extração química utilizando-se um solvente com menor impacto ambiental, que se mostrou adequado a tal fim. A extração térmica posterior dos ligantes foi realizada pelo aquecimento nas temperaturas de 250°C e 450°C sendo, posteriormente, a temperatura elevada a 900°C, para o início da sinterização. Utilizou-se atmosferas de Nitrogênio, Vácuo e Hidrogênio, com temperaturas de sinterização de 1250°C e 1330°, com tempos de patamares de 30 e 60 minutos. Verificou-se que as densidades atingidas nas atmosferas de Hidrogênio e Vácuo são semelhantes e se adequaram às especificações requeridas pela norma, enquanto a atmosfera de Nitrogênio resultou em características inferiores. As durezas e as resistências à corrosão obtidas com o uso das atmosferas de Hidrogênio e Vácuo foram também superiores as das amostras sinterizadas em atmosfera de Nitrogênio. / The powder injection molding process is used to manufacture parts with complex shapes, with high production demand. In orthodontic and medical applications, in which high hardness and corrosion resistance are required, 17-4 PH stainless steel is used by applying this forming technique. The sintering atmosphere is responsible for controlling the chemical reactions that occur during material densification and is critical to the ultimate product quality. This research study aims at evaluating the influence of the sintering atmosphere on the hardness and corrosion resistance of this type of steel. The removal of the primary binder was carried out by chemical extraction applying a solvent with less environmental impact, which has proved to be suitable for this purpose. The subsequent binder thermal extraction was held by heating at temperatures of 250°C and 450°C and, therefore, at temperature of 900°C, to initiate sintering. Nitrogen, vacuum and hydrogen atmospheres were used with sintering temperatures at 1250°C and 1330°, with 30 and 60 minute-step time. It was verified that the densities achieved in hydrogen and vacuum atmospheres are similar and suitable by the regulations, whereas the nitrogen atmosphere resulted in lower performance. The hardness and corrosion resistance obtained with the use of hydrogen and vacuum atmospheres were also higher than those obtained for samples sintered in the nitrogen atmosphere.

O processo de moldagem de pós injeção é utilizado para a fabricação de peças de geometrias complexas e com alto volume de produção. Em aplicações ortodônticas e médicas, nas quais são requeridas elevadas durezas e resistências à corrosão, o aço inoxidável 17-4 PH é utilizado aplicando-se aquela técnica de conformação. A atmosfera de sinterização é responsável pelo controle das reações químicas que ocorrem durante a densificação do material e são fundamentais para a qualidade final do produto. O objetivo deste trabalho foi avaliar a influência da atmosfera de sinterização na dureza e resistência à corrosão deste tipo de aço. A remoção dos ligantes primários foi realizada por meio de extração química utilizando-se um solvente com menor impacto ambiental, que se mostrou adequado a tal fim. A extração térmica posterior dos ligantes foi realizada pelo aquecimento nas temperaturas de 250°C e 450°C sendo, posteriormente, a temperatura elevada a 900°C, para o início da sinterização. Utilizou-se atmosferas de Nitrogênio, Vácuo e Hidrogênio, com temperaturas de sinterização de 1250°C e 1330°, com tempos de patamares de 30 e 60 minutos. Verificou-se que as densidades atingidas nas atmosferas de Hidrogênio e Vácuo são semelhantes e se adequaram às especificações requeridas pela norma, enquanto a atmosfera de Nitrogênio resultou em características inferiores. As durezas e as resistências à corrosão obtidas com o uso das atmosferas de Hidrogênio e Vácuo foram também superiores as das amostras sinterizadas em atmosfera de Nitrogênio. / The powder injection molding process is used to manufacture parts with complex shapes, with high production demand. In orthodontic and medical applications, in which high hardness and corrosion resistance are required, 17-4 PH stainless steel is used by applying this forming technique. The sintering atmosphere is responsible for controlling the chemical reactions that occur during material densification and is critical to the ultimate product quality. This research study aims at evaluating the influence of the sintering atmosphere on the hardness and corrosion resistance of this type of steel. The removal of the primary binder was carried out by chemical extraction applying a solvent with less environmental impact, which has proved to be suitable for this purpose. The subsequent binder thermal extraction was held by heating at temperatures of 250°C and 450°C and, therefore, at temperature of 900°C, to initiate sintering. Nitrogen, vacuum and hydrogen atmospheres were used with sintering temperatures at 1250°C and 1330°, with 30 and 60 minute-step time. It was verified that the densities achieved in hydrogen and vacuum atmospheres are similar and suitable by the regulations, whereas the nitrogen atmosphere resulted in lower performance. The hardness and corrosion resistance obtained with the use of hydrogen and vacuum atmospheres were also higher than those obtained for samples sintered in the nitrogen atmosphere.

Made available in DSpace on 2016-03-15T19:36:57Z (GMT). No. of bitstreams: 1 Dante da Costa Ribeiro.pdf: 1584757 bytes, checksum: 5a421e40bb3ea48cad64df542faaceb6 (MD5) Previous issue date: 2009-04-24 / Martensitic Stainless Steel hás always been used in the injection moulds because of their properties as high polishability and high corrosion resistence that alows it to inject some kind of polymers, such as PVC, because of its resistance to chlorinate gas that the process normally has, and in the injection of acrylic because of its high finishing surface state that the mould needs and, consequently, of the injected product, that are characteristics intrinsics to those materials. Beside the martensitic stainless steel, the stainless aged steel are very used, but, in such applications this steel are not able to suffer the nitriding process, what make its application not so good because there are no ways to increase its surface. In this paper will be studied about aged stainless steel that will pass through the shot peening process and without this process to see how will be the surface result. As there are no literatures about this subject, because besides it is about some old tecnologies, the study shall result in a new application of those techniques making a revolution in the utilization of those materials in some industrial applications as plastic moulds and mechanichal devices. / Os aços inoxidáveis martensíticos sempre foram muito utilizados no ramo de moldes plásticos devido as suas propriedades como alta polibilidade e resistência à oxidação elevada, que permitem a injeção de certos polímeros, como o policrilato de vinila, por conta de sua resistência aos gases clorídricos desprendidos no processo e também na injeção de acrílico por causa do alto grau de acabamento que pode ser conferida à superfície do molde e, conseqüentemente, ao produto injetado, são características intrínsecas a tais materiais. Fora os materiais inoxidáveis martensíticos, os endurecíveis por precipitação também são muitíssimo utilizados, porém, em algumas aplicações tais aços não são passíveis do processo termoquímico de nitretação, o que prejudica a sua utilização por conta de não ter nenhum processo onde um endurecimento superficial seja aplicado. Neste trabalho será realizado o estudo sobre os aços endurecíveis por precipitação passando pelo processo de shot peening e sem passar por tal processo afim de se verificar como ficará a superfície após tal processo. Como faltam literaturas sobre comparativos a respeito desta aplicação por apesar de se tratar de tecnologias antigas, o estudo poderá resultar em uma nova utilização de tais técnicas revolucionando a utilização destes materiais em certas aplicações industriais como em moldes plásticos e em dispositivos mecânicos.

No description available.

Additively manufactured (AM) 316L and 17-4PH stainless steel parts, concretely made by laser powder bed fusion (L-PBF), are characterized and micro-mechanical properties of those steels are analyzed. This study also explored and extended to proton irradiation and small-scale mechanical testing of those materials, to investigate how irradiation affects microstructural evolution and thus mechanical properties at the surface level, which could be detrimental in the long term in nuclear applications. In-depth anisotropy analysis of L-PBF 316L stainless steel parts with the variations of volumetric energy density, a combined study of nanoindentation with EBSD (electron backscatter diffraction) mapping is shown to be an alternative methodology for enriching qualification protocols. Each grain with a different crystallographic orientation was mapped successfully by proper indentation properties. <122> and <111> oriented grains displayed higher than average indentation modulus and hardness whereas, <001>, <101>, and <210> oriented grains were found to be weaker in terms of indentation properties. Based on an extensive nanoindentation study, L-PBF 17-4 PH stainless steels are found to be very sensitive to high load rates and irradiation further escalates that sensitivity, especially after a 0.25 s-1 strain rate. 3D porosity measurement via X-ray microscope ensures L-PBF stainless steel parts are of more than 99.7% density and could be promising for many industrial applications. High percentages of increment of nanohardness, maximum theoretical shear strength, and yield strength were observed due to proton irradiation of 5 um damage depth on the surface of 17-4 PH steel parts. Small-scale mechanical testing of irradiated AM nuclear stainless steels such as 17-4 PH was carried out and investigated by micro-compression of FIB fabricated pillars of different sizes of diameter. Irradiated 17-4 PH materials have never been investigated by this kind of testing procedure to asses the stress-strain characteristics of micro-scale volumes and to explore the structure-property relationship. Both as-built and irradiated AM 17-4 PH micropillars exhibited step-ups in the early stage of load-displacement curves with a varying number of slip bands intermittently formed throughout the pillar volume while compressed by the uniaxial load. As for the radiation-damaged zone, micropillars displayed lesser slip bands compared to as-built parts as irradiation damage creates an obstacle to dislocations movement and hence hardening. It requires higher loads to initiate plastic deformation as dislocation must overcome irradiation-induced obstacles for the slip to occur and localization of strain without increasing the load for a certain amount of time during the test. Proton irradiation effects on the compressive mechanical properties of AM 17-4 PH stainless steel parts depending on the volumetric energy density (VED) used during the parts' fabrication process. On as-built parts, compressive yield strength varied from 107.27 MPa to 150.70 MPa and it was in the range of 133.43 MPa to 244.57 MPa under irradiated conditions. All 2 μm pillars were fabricated as their height falls within the radiation damage depth of 5 μm. It was expected to generate the highest yield strength and tensile strength due to the radiation hardening effect as discussed earlier. Yield and tensile strength were found to be the highest as expected as of 244.57 MPa and 375.08 MPa in irradiated 17-4 PH sample 1 (VED = 54.76 J/mm3). Samples with lower VED exhibited better micro-mechanical compressive responses than higher VED AM 17-4 PH parts in both as-built and irradiated conditions.