Abstract To modify the surface structure of AISI 1005 steel and its properties without any dimensional loss, different plasma surface treatments were performed at low temperatures (500 ºC) in this study. The samples were subjected to single plasma treatments including: nitriding (N5% and N3%), carburizing (CE) and ferritic nitrocarburizing (NC) and to duplex treatments of nitriding followed by carburizing (N5%+CE and N3%+CE) and ferritic nitrocarburizing followed by carburizing (NC+CE). The gas mixture used for these treatments was varied as follows: nitriding (5%N2+95%H2 and 3%N2+97%H2), carburizing (5%CH4+95%H2) and ferritic nitrocarburizing (5%N2+1.5%CH4+93.5%H2). A microstructural characterization of the samples was carried out using optical and scanning electron microscopy in addition to XRD analysis. Microhardness testing was also performed. The XRD analysis showed a stabilization of the outermost cementite layer for all of the carburizing treatments. The results show that a greater hardness increase was achieved for the nitriding treatment as well as a more regular compound layer. However, a greater depth of hardening was obtained in samples with NC+CE and N5%+CE, which extended to the hardened depth to 800 µm.

In this work, plasma carburizing of sintered pure iron at low temperature was investigated. Samples were carburized under a dc abnormal glow discharge in two mixed atmospheres (5%CH4 + 95%H2 and 20%CH4 + 80%H2) at 500 °C and 700 °C for 3 and 6 hours. The influence of these parameters was investigated by Scan Electron Microscopy (SEM), X-ray Diffraction (DRX), Raman spectroscopy and microhardness measurements. There is a correlation between temperature and layer morphology, and a layer of polycrystalline cementite was obtained at 500 °C and 700 °C on a ferrite substrate. Furthermore, the carburized layer thickness increased with an increase in the treatment time and the methane percentage. The topography is very dependent on the treatment temperature.