Effect of Gas Pressure on Active Screen Plasma Nitriding Response

Abstract

An austenitic stainless steel AISI 304 was active screen plasma nitrided using a 304 steel screen to investigate the effect of the gas pressure on the nitriding response. The sample was treated for 18 ks at 723 K in 25 % N 2 ϩ 75 % H 2 . The gas pressure was changed to 100, 600, and 1200 Pa. The distance between the screen and the sample was also changed to 10, 30, and 50 mm. The nitrided samples were characterized by observing their appearance and surface roughness by optical microscopy, X-ray diffraction, and microhardness testing. After nitriding, polygonal particles with a normal distribution were observed at the center and edges of all the nitrided sample surfaces. The particles on the sample surface became finer with an increase in the gas pressure. The nitrided layer with a greater and homogeneous thickness was obtained at a low gas pressure of 100 Pa.

Effects of the Voltage and Pressure on the Carburizing of Martensitic Stainless Steel in Pulsed DC Glow Discharge

“…Concerning the influence of the processing parameters studied here, the literature is rich for austenitic stainless steels (ASSs) plasma nitriding [19][20][21][22][23][24][25][26][27][28][29] , but very poor for MSSs, being mainly focused on treated surface characteristics of different materials, through different processes [30][31][32][33][34][35][36][37][38][39][40] . It is to be noted that almost nothing has been published aiming to study such effects on the MSSs LTPC.…”

“…For ASSs, controversial results by comparing ref 19,20 . and ref [21][22][23][24] . have been reported for the pressure effects on the layer hardness and thickness, but all these authors agree very well that the pressure increment interestingly promotes an increase in the treated material corrosion resistance 20,[22][23][24] , possibly due to the combined effect of the Cr kept in the steel matrix solid solution and the protective layer formation 23,25 .…”

Inspection of contamination in nitrogen plasmas by monitoring the temporal evolution of the UV bands of NO-γ and of the fourth positive system of N2

“…As in DCPN, ASPN works under primary vacuum (0.3 to 12 mbar). [12][13][14][15] In ASPN, the surface of the metallic mesh is subjected to intensive ion bombardment and sputtered metallic species are deposited on the reactor walls. Metals can gettered water vapour during the opening of the reactor.…”

Confinamento de elétrons em um sistema de plasma de tela ativa e geração de potencial flutuante extremo no interior da gaiola catódica

“…Recentemente, seu uso foi estendido para outros tipos de materiais, como a funcionalização superficial de materiais poliméricos e fibras de carbono 1,3-5. Nos tratamento com Gaiola Catódica são minimizados os danos devido à minimização do bombardeamento por íons energéticos do plasma, mantendo as espécies ativas geradas na região luminescente, as quais podem se difundir e reagir com as superfícies das peças dentro da gaiola5. Os efeitos dos parâmetros de tratamento com gaiola catódica, como o tamanho da malha, a distância entre a amostra e a tela, a pressão do gás de trabalho, a composição do gás, a geometria da peça a ser tratada, o potencial aplicado e, mais recentemente, a área aberta da tela, já foram estudados por diferentes autores 3,[6][7][8][9][10][11][12][13][14][15][16][17][18][19] . No entanto, esses estudos se concentraram principalmente nas propriedades das camadas tratadas.…”