Model for Predicting Microhardness Profiles of Steel after Nitriding
AbstractThe plasma nitriding process produces a hard near-surface thin layer of the nitrided material. The thickness of the diffused layer, produced in the course of this process, is between 0.001 and 0.6 mm. The paper presents a study of influence of the nitriding temperature, pressure, and time on the steel microhardness profiles. The one-dimensional transient diffusion model is applied to a thin nitride layer. That allows one to predict the material hardness distribution within the near-surface layer as a function of time for a modified nitrogen diffusion coefficient. The temperature and pressure dependence of the diffusion coefficient is considered. Hence, the model involves the reaction rates of nitrides formation. The solution thus obtained is compared with experimental data for a decrease of hardness as a function of depth and time, until the core hardness is reached.
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