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In this work,the effect of nitriding current density on hardness,crystalline phase composition,layer thickness and corrosion rate of AISI 4340 steel has been studied.X-ray diffraction analysis shows that thin layers formed during nitriding process are constituted of y-Fe_4N for samples processed between 1 and 2.5 mA/cm~2. Thickness of nitrided layer increases proportionally to current density(0μm for 0.5 mA/cm2 to 1 5μm for 2.5 mA/cm~2).Plasma nitriding increased the surface hardness from 300 HV_(50g) for untreated sample,to around 800HV_(50g) for nitrided samples at 1 mA/cm~2.While the untreated samples exhibited a corrosion rate of 0.153 mm per year,the corrosion performance was improved up to 0.03 mm per year at current densities above 1 mA/cm2,which is about one fifth of the corrosion rate of the untreated sample.
In this work, the effect of nitriding current density on hardness, crystalline phase composition, layer thickness and corrosion rate of AISI 4340 steel has been studied. X-ray diffraction analysis shows that thin layers formed during nitriding process are composed of y-Fe_4N for Samples were processed between 1 and 2.5 mA / cm ~ 2. Thickness of nitrided layer increased proportionally to current density (0 μιη for 0.5 mA / cm2 to 1 5 μιη for 2.5 mA / cm ~ 2) 50g) for untreated sample, to around 800HV_ (50g) for nitrided samples at 1 mA / cm ~ 2.While the untreated samples exhibited a corrosion rate of 0.153 mm per year, the corrosion performance was improved up to 0.03 mm per year at current densities above 1 mA / cm2, which is about one fifth of the corrosion rate of the untreated sample.