PRESSÃO DO GÁS DE TRABALHO COMO PARÂMETRO DE CONTROLE DE FASES CRISTALINAS OBTIDAS EM NITRETAÇÃO POR PLASMA PULSADO
WORKING GAS PRESSURE AS A CONTROL PARAMETER OF CRYSTALLINE PHASES DURING PULSED PLASMA NITRIDING PROCESS
Scholtz, Juliano Sadi; Ludero, Alex; Mezaroba, Marcello; Torres, Ricardo Diego; Fontana, Luis Cesar
Resumo
Este trabalho apresenta resultados experimentais que indicam a possibilidade de selecionar a fase cristalina obtida com nitretação por plasma pulsado, permitindo-se escolher entre a camada monofásica ε-Fe2-3N e/ou γ’-Fe4 N na camada branca. Os experimentos foram realizados em amostras de aço baixo carbono AISI 1015, tratadas com plasma em atmosfera N2 /H2 , em pressões entre 100Pa e 1400Pa numa temperatura de 500°C. Foram aplicados pulsos bipolares de tensão de curta duração em frequência de 125kHz (pulsos negativos com duração de 7,5 μs intercalados a pulsos positivos de 0,5 μs). As amostras foram caracterizadas por DRX e MEV, e os resultados indicam que a pressão do gás de trabalho pode ser usada como um parâmetro se
Palavras-chave
Abstract
This paper presents experimental results that indicate the possibility of selecting the crystalline phase obtained by nitriding pulsed plasma, allowing the choice among the ε-Fe2-3N and γ’-Fe4N single-phase layers formed under the sample surface, in the white layer. AISI 1015 low carbon steel samples were treated with pressures between 100 Pa and 1400 Pa at 500°C. Short bipolar pulses of voltage were applied at 125kHz to perform the plasma nitriding. The XRD and SEM results show that the increase in the pressure favors the selection of γ’-Fe4N.
Keywords
Referências
1 Łępicka M, Grądzka-Dahlke M. Direct current and pulsed direct current plasma nitriding of ferrous materials: a critical review. Acta Mechanica et Automatica. 2016;10(2). http://dx.doi.org/10.1515/ama-2016-0024.
2 Sirin SY, Sirin K, Kaluc E. Effect of the ion nitriding surface hardening process on fatigue behavior of AISI 4340 steel. Materials Characterization. 2008;59(4):351-358. http://dx.doi.org/10.1016/j.matchar.2007.01.019.
3 Lepienski CM, Nascimento FC, Foerster CE, Da Silva SLR, Siqueira CJM, Alves C Jr. Glow discharge nitriding in AISI 304 at different nitrogen-hydrogen atmospheres: structural, mechanical and tribological properties. Materials Science and Engineering A. 2008;489(1-2):201-206. http://dx.doi.org/10.1016/j.msea.2007.12.012.
4 Sato S, Arai Y, Yamashita N, Kojyo A, Kodama K, Ohtsu N, et al. Surface-nitriding treatment of steels using microwave-induced nitrogen plasma at atmospheric pressure. Applied Surface Science. 2012;258(19):7574-7580. http://dx.doi.org/10.1016/j.apsusc.2012.04.090.
5 Nagamatsu H, Ichiki R, Yasumatsu Y, Inoue T, Yoshida M, Akamine S, et al. Steel nitriding by atmospheric-pressure plasma jet using N2 /H2 mixture gas. Surface and Coatings Technology. 2013;225:26-33. http://dx.doi.org/10.1016/j. surfcoat.2013.03.012
6 Sousa RRM, Moura YJL, Sousa PAO, Medeiros JQ No, Costa THC, Alves C Jr. Nitriding of AISI 1020 steel: comparison between conventional nitriding and nitriding with cathodic cage. Materials Research. 2014;17(3):708-713. http://dx.doi.org/10.1590/S1516-14392014005000027.
7 Hamann S, Börner K, Burlacov I, Spies H-J, Strämke M, Strämke S, et al. Plasma nitriding monitoring reactor: a model reactor for studying plasma nitriding processes using an active screen. The Review of Scientific Instruments. 2015;86(123503)
8 Weber T, Wit L, Saris FW, Königer A, Rauschenbach B, Wolf GK, et al. Hardness and corrosion resistance of single-phase nitride and carbide on iron. Materials Science and Engineering A. 1995;199(2):205-210. http://dx.doi.org/10.1016/0921-5093(94)09729-1.
9 O’Brien JM, Goodman D. Plasma (ion) nitriding. ASM International; 1991. p. 420-424. vol. 4.
10 Corengia P, Ybarra G, Moina C, Cabo A, Broitman E. Microstructural and topographical studies of DC-pulsed plasma nitrided AISI 4140 low-alloy steel. Surface and Coatings Technology. 2005;200(7):2391-2397. http://dx.doi.org/10.1016/j.surfcoat.2005.01.060.
11 Wang S, Cai W, Li J, Wei W, Hu J. A novel rapid D.C. plasma nitriding at low gas pressure for 304 austenitic stainless steel. Materials Letters. 2013;105:47-49. http://dx.doi.org/10.1016/j.matlet.2013.04.031.
12 Callister WD Jr. Materials science and engineering: an introduction. New York: John Wiley & Sons; 1991.
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