Abstract
This paper describes the development of a simulation program to model gas nitriding processes for steels and replace traditional trial-and-error methods that are expensive, time-consuming, and often inaccurate. The authors introduce a compound layer growth model that simulates key nitriding outcomes, including phase composition, compound layer thickness, and nitrogen concentration profiles based on process parameters (temperature, time, and nitriding potential or dissociation rate). The model employs computational thermodynamics to construct alloy-specific Lehrer diagrams that describe phase stabilities, uses parabolic law to simulate compound layer growth kinetics, and applies constant effective nitrogen diffusivity in the diffusion zone for specific alloys at given temperatures. Validation testing on AISI 4140 steel under various nitriding conditions demonstrated excellent agreement between simulated and experimental results for both as-washed and pre-oxidized specimens, confirming that the software provides an effective tool for determining optimal nitriding parameters to meet specifications and ensure reliable performance through accurate process control.
