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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Desenvolvimento de um sistema de nitreta??o por plasma em fonte pulsada e sua influencia sobre a nitreta??o do tit?nio

Oliveira, Jos? Antonio Bernardino de 15 October 2011 (has links)
Made available in DSpace on 2014-12-17T14:06:56Z (GMT). No. of bitstreams: 1 JoseABO_DISSERT.pdf: 1955916 bytes, checksum: ab738b441db6538b6bc4159b47e66186 (MD5) Previous issue date: 2011-10-15 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The pulsed plasma nitriding is a solution currently used in the metallurgical industry to resolve problems earlier in the processing of parts by using plasma DC voltage. These problems consisted mainly of edge effect and opening arches caused due to non-uniformity of electric fields on uneven surfaces. By varying the pulse width can reduce these effects. However, variations in pulse width can drastically affect the population of the plasma species and hence the final microstructure of the nitrided layer. In literature, little is known about the effect of process parameters on the properties of the plasma species and, consequently, the surface properties. We have developed a system of nitriding with pulsed source with fixed period of 800  pulse width is variable. Examined the variation of these parameters on the properties of nitrided surface when keeping constant temperature, gas composition, flow, pressure and power. It was found that the values of width and pulse repetition time of considerable influence in the intensities of the species present in plasma. Moreover, we observed the existence of the edge effect for some values of pulse widths, as well as changes in surface roughness and hardness / A nitreta??o por plasma pulsado ? uma solu??o utilizada atualmente na ind?stria metal?rgica para resolver problemas existentes anteriormente durante tratamento de pe?as usando plasma de tens?o cont?nua. Esses problemas consistiam, principalmente, em efeito de bordas e abertura de arcos causados devido a n?o uniformidade de campos el?tricos em superf?cie irregular. Atrav?s da varia??o da largura do pulso ? poss?vel reduzir estes efeitos. Entretanto, as varia??es de largura de pulso podem afetar drasticamente a popula??o de esp?cies do plasma e, conseq?entemente, a microestrutura da camada nitretada final. Na literatura, pouco se sabe sobre o efeito dos par?metros do processo nas propriedades das esp?cies do plasma e, conseq?entemente, nas propriedades superficiais. Neste trabalho foi desenvolvido um sistema de nitreta??o com fonte pulsada com per?odo fixo de 800 s e largura de pulso vari?vel. Analisou a varia??o desses par?metros sobre as propriedades da superf?cie nitretada quando se mant?m constantes a temperatura, composi??o do g?s, fluxo, press?o e pot?ncia. Verificou-se que os valores da largura e tempo de repeti??o do pulso influem fortemente nas intensidades das esp?cies presentes no plasma. Al?m disto, foi observada a exist?ncia do efeito de borda para alguns valores de larguras de pulso, bem como varia??o na rugosidade e dureza superficiais

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