Nitriding without the compound layer and with continuous in-process variation of the nitriding potential

In the paper is presented results of nitriding of alloy steel without white layer and are described mathematical relationship for continuously change the nitriding potential during process. It is advisable to reduce the value of the nitriding potential as time of process proceeds, in order not to exceed the border concentration of nitrogen in the diffusion zone, which would cause the formation of the ε (Fe2-3N) or γ(Fe4N) phases on the steel surface. The highest rise of the diffusion zone occurs when the nitriding potential KN of the atmosphere corresponds to the upper limit of nitrogen concentration in the α zone (diffusion nitrided layer). Further increase of the nitriding potential causes the formation on the steel surface of the ε phase and with the rise in the thickness of the ε zone, there comes about a reduction in the rate of growth of the zone with the α phase. Copyright © 2007 Inderscience Enterprises Ltd.