New possibilities for controlling gas nitriding process by simulation of growth kinetics of nitride layers

Abstract

This paper presents results of computerised simulations of the gas nitriding process, demonstrating the influence of the nitriding potential of NH₃–H₂ atmosphere on the composition and growth kinetics of γ′ and ɛ nitride layers on pure iron. For the simulation, the recently developed K_N–T phase diagram and growth kinetics models for both phases were utilised, as well as the latest results of experimental research. Simulation results indicate optimum possibilities of process control for the formation of layers of predictable phase composition, thickness of particular zones, and surface nitrogen concentrations. Also included are data on growth kinetics of the nitride layer (ɛ/γ′ and α zones) on alloy steels. The role of nitride forming and other alloying elements in process kinetics is discussed.