Mathematical modelling and computer simulation of nitriding

Abstract

Mathematical modelling of matter transmission during gas nitriding has been deduced by a numerical calculation in the present study. The diffusion coefficient of nitrogen in 38CrMoAl steel and the matter transmission coefficent in the interfacial reaction have been measured. Owing to the large difference between the nitrogen activity at the surface of the workpiece and that of the gas phase during the nitriding process, it is very difficult to control the nitrogen potential and balance the nitrogen activity. In order to solve this problem, is it proposed that the nitrogen potential is dynamically controlled by computer. Under conditions of high nitriding speed, the computer controlled technique used in practical manufacture shows good reproducibility and can control the nitrogen potential accurately, thereby reducing the brittleness of the nitrided layer.