Modeling of nitride layer formation during plasma nitriding of iron

Mathematical Modeling of Discharge Plasma Generation and Diffusion Saturation of Metals and Alloys

“…-the qualitative agreement of results of present model with the researches of other authors [12,16] and experimental data [7].…”

“…The mathematical model of nitriding describes the layer growth kinetics and nitrogen profile concentration at each phase and diffusion zone during ion nitriding of metal. There has been an ongoing effort on the simulation of layer growth kinetics and nitrogen concentration profiles in ion nitriding during the last decades [12][13][14][15][16]. In building the mathematical model of the problem the following assumptions are made: mass balance at the interfaces considers equal specific volumes, flow is one-dimensional, diffusion coefficients are constant at each phase and diffusion zone, the temperature at every point in the specimen is identical during the whole process, the surface erosion and layer growth occur in plane fronts parallel to the specimen surface, evolution of phases takes place under thermodynamical equilibrium conditions.…”

“…In this case, we have three phases: ε-phase, γ'-phase and α-phase [12,16]. According to the data from the literature with the assumption of equilibrium in the Fe-N system, the initial and boundary conditions can be expressed as: concentration of nitrogen in ε-Fe 2-3 N nitride reaches 11.14 -7.71 wt %, concentration of nitrogen in γ' nitride is in the range of 5.76 to 5.91 wt %.…”

“…Maximum solubility of nitrogen in α-iron, at 590 o C and at the equilibrium with γ' nitride, can be considered approximately С α ≈ 0.1 wt %. In this way the nitrogen concentration at interfaces between the ε, γ' and α layers can be expressed as: С ε/γ' ≈ 7.71 wt %, С γ'/ε ≈ 5.91 wt %, С ≈ 5.76 wt % [16].…”

“…The complexity and multiple relations of nitriding process make difficult to define the general laws in the structuration of modified layers and their properties [12][13][14][15][16]. Such problems can be solved by mathematical modeling of the processes in plasma generation and material nitriding.…”