Finite element investigation of multi-phase transformation within carburized carbon steel

Mechanical components for the automobiles, aircrafts and machines are required to have the higher strength, hardness and wear resistance, when these parts are generally subjected to high load and impact. Such mechanical properties can be obtained from the carburization and quenching processes. Thus, in this study, numerical investigation using three-dimensional finite element technique was made to simulate the carburization and multi-phase transformation processes within the carburized carbon steel during quenching. In order to simulate the carburization process, the second Fick's equation and carbon diffusional equation were adapted. For numerical simulation of the diffusional phase transformation occurred during the non-isothermal quenching process, subdivision of the cooling curve into various small isothermal steps was introduced with the help of various time–temperature–transformation (TTT) diagrams of carbon steel. In addition, Scheil's additive rule and Johnson–Mehl–Avarami–Kolmogorov (JMAK) equation were also solved. On the other hand, Koistinen and Marburger's equation was used to model the diffusionless transformation. Through numerical analyses of carburization and quenching processes, the temperature and volume fraction of each phase were predicted for simple cylindrical specimen and complex geometries considering the latent heat generated during phase transformation. The numerical results compared well with the data available in the literature.