Killian LEMONNIER, a PhD candidate in the MSE Team at LaBoMaP, will defend his doctoral research in Amphitheater II on the Arts et Métiers Cluny campus or remotely via Microsoft Teams.

The thesis defense will take place on Thursday, October 8, 2026, at 2:00 PM, in Amphitheater II at the Arts et Métiers Cluny campus.

Title

Study of post-casting metallurgical transformations in grey cast irons to improve machinability in turning operations

Abstract

This PhD research topic addresses an industrial issue encountered at the Renault Le Mans plant concerning the machining of cast iron brake discs produced through the green sand-casting process. More specifically, when brake discs are machined immediately after casting during the finishing operation of the braking surfaces, cutting tool wear occurs at an abnormally high rate. To date, the only effective countermeasure has been to machine the discs between one week and one month after casting. Existing studies on the subject report a slight structural hardening after casting, characterized by an initial phase of rapid evolution during the first seven days followed by near-complete stabilization after approximately fourteen days. The primary parameter governing the occurrence of the maturation phenomenon is the presence of free nitrogen, that is, nitrogen not trapped by nitride-forming elements such as titanium. Furthermore, manganese content has also been shown to influence the phenomenon, acting as an inhibitor in some cases while promoting it in others. These observations have led to the hypothesis that the precipitation of iron nitrides within the cast iron matrix may explain the maturation phenomenon.
Accordingly, the main outcomes of this research are organized around three key objectives:

• Development of a maturation behavior model coupling the effects of nitrogen and manganese;
• Identification and characterization of the precipitates involved in the maturation phenomenon using Differential Scanning Calorimetry (DSC) and Transmission Electron Microscopy (TEM);
• Proposal of a preliminary explanation for the relationship between cast iron maturation and machinability.

Keywords

Grey cast iron, Aging, Age Strenghtening, Machinability, Foundry, Iron nitride, MET, DSC

Jury Members

• Mme Stéphanie BRUYERE, Associate professor HDR, IJL Nancy, Reviewer
• M. Manuel de JESUS CASTRO ROMAN, Full professor, CINVESTAV Saltillo, Reviewer
• M. David BALLOY, Full professor, Université de Lille, Examiner
• M. Philippe JACQUET, Associate professor HDR, LaBoMaP Cluny, Supervisor
• M. Alexis VAUCHERET, Associate professor, LaBoMaP Cluny, Co-Supervisor
• M. Frédéric ROSSI, Associate professor, LaBoMaP Cluny, Co-Supervisor
• M. Frédéric TRITZ, Technical leader foundry process, Renault Le Mans, Guest
• M. Pierre-Yves BRAZIER, Director Ecole Supérieure de Fonderie et de Forge, ESFF Châlons en Champagne, Guest

Practical Information

Location:

Zimberlin Amphitheater II, Campus Arts et Métiers de Cluny
13 rue Porte de Paris, 71250 Cluny

Teams link
To attend the defense remotely: Click here

More information
See the PhD candidate’s profile: Click here