Multi-objective optimization of steel nitriding

P. Cavaliere, A. Perrone, A. Silvello

CHALLENGE - Steel nitriding is a thermo-chemical process largely employed in the machine components production to solve mainly wear and fatigue damage in materials. Here we describe the behavior of nitriding process on different steels (40 different materials) in a broad range of processing parameters leading to the description of the effect on the steel structures and subsequent mechanical properties. 

SOLUTION - The objective of this study is the maximization of surface and bulk hardness of nitrided steel. Steel cylindrical samples 100 mm in diameter were nitrided by varying the nitrogen potential, nitriding temperature and time. In the present study response surfaces (RS) that are best suited to deal with a multi-objective optimization were obtained. The optimization software used is modeFRONTIER, through which a set of input parameters (steel composition, nitrogen potential, nitriding time, etc.) was set and evaluated on the basis of an optimization algorithm. The calculations led to the definition of the independent coefficients solved by ANSYS through modeFRONTIER by matching in closed loops the solutions with the experimental data. 

BENEFITS  - The experimental results of the present study using modeFRONTIER demonstrate that the nitrogen potential influences the maximum hardness values on the surface. On the contrary, the nitrogen potential does not influence the hardness profile, it is strongly influenced by the steel composition.