The effect of nitrocarburizing parameters on the corrosion resistance of sintered steel

The Response Surface Method (RSM) was employed to optimize the nitrocarburizing temperature and time as applied to a sintered steel of composition 3.8 Mn - 0.4 C - Fe (in wt.%). The remaining experimental parameters were unchanged: atmosphere (1.25% CH4 - 23.75% H-2 - 80% N-2), pressure (400 Pa), and gas flow (4 x 10(-6) m(3)/s). The samples were characterized according to the thickness of the nitrided layer, microhardness profile and corrosion resistance. The results showed that the thickness of the compound layer increased with the nitrocarburizing temperature and time, thus improving the corrosion resistance of the material. In addition to the thickness of the compound layer, the corrosion behavior was also affected by the nature of the protective layer. Further improvements were achieved when epsilon - Fe2-3N was preferentially formed.