Abstract
The nitriding behaviour of 34CrAlNi7 alloy steel was investigated under three different nitriding processes. One of them is salt-bath nitriding that was carried out at a temperature of 525 °C for treatment time of 1, 2 and 3 h. The others are ion nitriding and fluidized bed nitriding that were conducted at 500 °C and 540 °C, respectively, in treatment time of 6, 12 and 18 h. The thickness of compound layer, measured by means of a digital thickness instrument attached to optical microscope, ranged from 3 µm to 16 µm depending on nitriding technique and treatment time. The presence of γ'-Fe₄N and ε-Fe_2-3N phases formed in the compound layer was confirmed by XRD analysis. Kinetics studies showed that the effective diffusion coefficients are 453 x 10^-14, 77.8 x 10^-14 and 278 x 10^-14 m²s^-1 for salt bath, plasma and fluidized bed processes, respectively.

Key words
plasma nitriding, fluidized bed nitriding, 34CrAlNi7 steel

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