Glow-discharge nitriding of ISO 5832-1 austenitic stainless steel: Influence of treatment time

Samples of stainless steel ISO 5832-1 were nitrided in gas mixture of 90% N-2 and 10% H-2 at a temperature of 630 C. The treatment time was selected in 1, 3 and 5 hours. Treated samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and Vickers microhardness, besides the analysis of the mass variation. The results evidence the no diffusion growth of the compound layer. The increase time, of 1 for 3h, to cause a larger incorporation of nitrogen in the surface of the material accompanied of formation the richer phases in that element. Also cause the increase of hardness and mass, as well as growth of the nitrided layer. The processing accomplished by 3 and 5 h present similar results. This is due the formation of a rich superficial layer in nitrites that inhibits the entrance of nitrogen for the interior of the sample.