| This work was initiated to examine the effect of frequency and treatment temperature on the formation of nitrided layers and surface characteristics during plasma nitriding. Plasma nitriding experiments were performed with 316L austenitic stainless steel at the temperatures 440℃ and 500℃ using a pulsed d.c. plasma with various frequencies in art atmosphere of N₂-H₂ gas mixture. The microstructure and thickness of the nitrided layer and morphology of the nitrified surface were investigated using OM, SEM, XRD, EDS and AFM. XRD patterns revealed that the surface layer formed at 400℃ consisted of S phase only and CrN+Fe₄N nitrides at 500℃, and no change of phase composition, with frequency was observed, The compound layer thickened slightly with increased frequency. Also, the surface roughness increased as the frequency of the pulsed plasma increased from 50 to 5,000㎐. |
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