Theoretical Considerations on Transition Metals Sulphides Precipitation in Alloyed Steels

— Mechanical properties of alloyed steels parts may be improved by precipitation of simple and/or complex chemical combinations (carbides, nitrides, and/or carbonitrides) using thermal and/or thermo-chemical treatments. Nevertheless, the precipitation of transition metal sulphides (TMSs) is considered as an undesirable phenomenon because of the negative influence on the material properties. This phenomenon has been the object of several theoretical studies (phenomenological description, thermodynamical and/or kinetical approaches) and is still under focus. In this study, the theoretical approach to this phenomenon is carried out on the basis of the non-dimensional mathematical analysis (collection and mathematical modelling of specific data bank). We propose a relative ranking of sulphidising ability for transition metals (TMs) and models to compute any TMS amount and relative content in the metallic structure of Fe-C alloys.