Estudo das variáveis de sinterização a plasma em aço inoxidável austenítico
Through the plasma assisted sintering process, also known as glow discharge sintering, the compacted powder is subjected under a luminescent discharge cloud of ionized gas. The ionized gas interacts with the surface of the sample and allows its heating, densifying the particulates. Plasma sinterin...
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| Formato: | Dissertação |
| Idioma: | pt_BR |
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| Endereço do item: | https://repositorio.ufrn.br/jspui/handle/123456789/27649 |
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| Resumo: | Through the plasma assisted sintering process, also known as glow discharge sintering, the compacted
powder is subjected under a luminescent discharge cloud of ionized gas. The ionized gas interacts with
the surface of the sample and allows its heating, densifying the particulates. Plasma sintering methods
can produce materials with high degrees of performance. The sintering process can be done under
highly reductive atmospheres, fine temperature control and reduced processing time compared to
conventional sintering methods. This work proposes to analyze the effects of plasma sintering on
austenitic stainless steel AISI 316L. It is intended to evaluate the effects of different treatment
parameters on sintering in order to determine which ones are best suited to the production of sintered
samples with good densification. The treatment parameters used in the first stage of the research were
700MPa compaction pressure, argon atmosphere, with 30 minutes holding time of sintering at an
apparent temperature of 730°C. In this stage, sintering was performed using planar hollow cathode and
cylindrical hollow cathode. The samples were evaluated for relative porosity, pore geometry and
cathode heating rate. It was observed that sintered samples using a hollow cylindrical cathode showed
reduced porosity with high degree of circularity. Then, using cylindrical hollow cathode, under the
same sintering parameters, the effects of the variation of the compaction pressure on the samples were
evaluated. Pressures of 555MPa, 655MPa, 700MPa, 750MPa and 800MPa were used. In sintered
samples, pore geometry and distribution, grain size, crystal structure, apparent hardness and
microhardness of the samples were studied. The samples compressed at 750MPa and 800MPa and
sintered presented the best results. Samples compacted at 800MPa were subjected to sintering under
heating rates of 9,17°C/min (+0,01A/min), 18,8°C/min (+0,02A/min) and 36,8°C/min (+0,05A/min).
The pore morphology and its distribution were evaluated, the densities of the samples were measured.
The sintered samples produced with heating rate of 18,8°C/min (+0,02A/min) showed better results.
Finally, in order to evaluate the influence of isotherm time, processes with 5 minutes, 15 minutes and
30 minutes of holding time were performed. The samples were compacted at 800MPa, with heating
rate of 18,8°C/min (+0,02A/min), applying argon atmosphere and isotherm temperature of 730°C. The
microhardness, the geometry and pore distribution and the densification of the sintered samples were
evaluated. The sintered samples processed with 30 minutes of holding time presented better
densification. The plasma sintered samples processed with 15 min of holding time also showed good
densification, allowing a reduction in treatment time. The parameters for plasma sintering were
evaluated and defined throughout the research steps, resulting in adequate densifications for AISI
316L steel. Finally, sintered samples using a hollow cylindrical cathode, compressed at 800MPa, with
heating rate of 18.8°C/min (+0.02A/min) and sintering times of 30 minutes showed a densification of
28%, a sintered final density of 84.77% and an apparent porosity percentage of 1.374%. |
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