Prediction of carbon concentration profile within carburised-carbon steel 1024 using Alternating Direction Implicit (ADI) method

Abstract

Pack carburisation is recognised to improve the carbon surface content of carburised-carbon steel 1024 that enhance the surface hardness and further can be used in automobiles, form implements, machines, gears and springs. The transient two-dimensional diffusion equation that represents the carbon concentration profile within the carburised-carbon steel 1024 is discretised using Alternating Direction Implicit (ADI) technique. A semi-analytical method is used to verify the ADI method and the numerical algorithm is developed in MATLAB software. To materialise the pack carburisation process, the boundary condition, initial condition and step time are encoded to signify the experiment conditions from the literature. The simulation results successfully predicted the carbon concentration profile within the carburised-carbon steel 1024 with variation of carburisation time (2 hours to 60 hours) and temperature (900°C - 1000°C). The effect of carburisation time and temperature are evaluated and the relation of both effects on the carbon development is explained. Simulation results show that carburisation extended to 60 hours only increases the carbon content at the core to 0.3wt % from 0.24 wt% of its original content. The small increment is satisfactory to maintain its ductility by hardening the surface.