Cathodic cage plasma nitriding of austenitic stainless steel (AISI 316): influence of the working pressure on the nitrided layers properties
AUTOR(ES)
Sousa, R.R.M. de, Araújo, F.O. de, Gontijo, L.C., Costa, J.A.P. da, Nascimento, I.O., Alves Jr, C.
FONTE
Mat. Res.
DATA DE PUBLICAÇÃO
06/12/2013
RESUMO
In this work, the influence of working pressure on the characteristics of the layers produced by the nitriding treatment on the AISI 316 austenitic stainless steel surface using the Cathodic Cage Plasma Nitriding technique (CCPN) is assessed. The treatments were carried out at a temperature of 723 K for 5 hours under working pressures of 120, 250 and 500 Pa. The morphology, microstructure and corrosion resistance were studied through optical microscopy, x-ray diffraction, and electrochemical potential curves. We analyzed the effects of working pressure on the layer thickness, microhardness and corrosion resistance. The E×i curves and the electrochemical impedance of polarized samples were measured in order to investigate the effect of the ion transfer inside the produced film placed into the anodic solution. The electrochemical impedance of the films were measured, and showed an apparent capacitive behavior. For treatment under a pressure of 120 Pa we found the nitrides Fe3N, Fe4N and CrN. For treatment at a pressure of 250 Pa, the CrN disappears and the observed phases are the nitrides Fe3N, Fe4N and the S-phase. For a treatment pressure of 500 Pa there is an increase in the corrosion resistance of nitrided layers, confirmed by the predominance of S-Phase in the x-ray diffraction pattern. On the other hand, the sample nitrided under the pressure of 250 Pa showed very unstable impedance behavior when immersed in NaCl solution, indicating that the treatment at this specific working pressure has a negative effect on the corrosion resistance of plasma nitrided AISI 316 stainless steel surfaces.
Documentos Relacionados
- Investigating the correlation between some of the properties of plasma nitrided AISI 316L stainless steel
- Cathodic cage nitriding of AISI 409 ferritic stainless steel with the addition of CH4
- Low-temperature plasma nitriding of sintered PIM 316L austenitic stainless steel
- Nitriding using cathodic cage technique of martensitic stainless steel AISI 420 with addition of CH4
- Nitriding of AISI 1020 steel: comparison between conventional nitriding and nitriding with cathodic cage