Nitretação por plasma de aço inoxidável austenítico com fluxo pulsado de nitrogênio
Plasma nitriding of austenitic stainless steel is a very useful thermochemical treatment to provide enhancement of surface tribological characteristics through the formation of expanded austenite. This work initiates a new research line using pulsed nitrogen gas flow during the D.C. plasma nitriding...
| Autor principal: | Sphair, Anna Carolina |
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| Formato: | Dissertação |
| Idioma: | Português |
| Publicado em: |
Universidade Tecnológica Federal do Paraná
2018
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| Assuntos: | |
| Acesso em linha: |
http://repositorio.utfpr.edu.br/jspui/handle/1/2970 |
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| Resumo: |
Plasma nitriding of austenitic stainless steel is a very useful thermochemical treatment to provide enhancement of surface tribological characteristics through the formation of expanded austenite. This work initiates a new research line using pulsed nitrogen gas flow during the D.C. plasma nitriding of AISI 316L done at low temperatures (400ºC) and short times (1 to 4h). The pulsed gas flow is proposed as a control parameter for the properties of the expanded austenite layer and consists of nitriding with intermittent nitrogen gas flow inside the reactor. Cycles with periods of offer and break off of gas flow were repeated during the treatments. In order to investigate the effects of the periods with gas offer and break off, different pulses condition were investigated on which the nitrogen gas flow represented 10, 20, 25 or 50% of the cycle’s time. For comparison treatments with continuous gas flow were realized while the other treatment parameters were maintained in order to isolate the pulses effects. The results show that for conditions using intermittent gas flow with 25% and 50% of nitrogen offer, the layer parabolic grow rate, the layer thickness and hardness were very similar to those obtained for treatments with continuous nitrogen flow. In relation to the conditions of pulses with 10 and 20% of nitrogen offer, obtained results presents more pronounced differences in comparison to treatments with continuous flow. However, even for this situation the results are significant. Therefore it is concluded that the pulsed gas flow can be used as a control parameter of the expanded austenite properties. In addition the use of nitrogen pulses can promote saving on the volume of gas that is used during the plasma nitriding maintaining similar properties to the continuous treatments. |
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