TY - BOOK

T1 - Inductive heat treatment of a 50CrMo4 steel- evolution of microstructure and mechanical properties

AU - Eggbauer, Annika

N1 - no embargo

PY - 2018

Y1 - 2018

N2 - This work elucidates the effects of fast heat treatments on the microstructure evolution and mechanical properties of a 50CrMo4 steel. Fast austenitizing and tempering heat treatments, such as induction heat treatments offer the possibility of increased productivity and energy savings during the process compared to a furnace treatment. However, it needs to be understood, how fast heat treatments affect the microstructure and mechanical properties of materials. To this end, this study exclusively focuses on the effects of high heating rates and different end-temperatures on two prior microstructures of a 50CrMo4 steel. Different heating devices, from a dilatometer up to a lab scale induction heating generator were used for the heat treatments, while microstructure was studied with a combination of high resolution techniques, such as Scanning and Transmission Electron Microscopy and 3D Atom Probe Tomography. Through detailed analysis of every single process step it could be shown that an inductive quench and tempered process leads to increased hardness and toughness properties compared to a conventional furnace heat treatment, if the process parameters are adapted favorably. This study focused on all process parameters of induction heat treatments and elucidates the influences of heating rates and temperatures on the resulting microstructure and mechanical properties. Fast austenitizing treatments with high heating rates (10-100K/s) might lead to insufficient time for homogenization and carbide dissolution during austenitization which results in higher transformation temperatures. Inhomogeneities within the austenitic matrix result in increased strain in the martensitic crystal structure after quenching. However, during tempering the increased strain within the martensitic matrix leads to an increased amount of nucleation sites for tempering carbides and to smaller tempering carbides and therefore beneficial hardness and toughness properties. This work contributes also to the knowledge of the influences of processing parameters on the microstructure evolution and mechanical properties, which can be helpful to set up processes with higher productivity but without deterioration of the material properties.

AB - This work elucidates the effects of fast heat treatments on the microstructure evolution and mechanical properties of a 50CrMo4 steel. Fast austenitizing and tempering heat treatments, such as induction heat treatments offer the possibility of increased productivity and energy savings during the process compared to a furnace treatment. However, it needs to be understood, how fast heat treatments affect the microstructure and mechanical properties of materials. To this end, this study exclusively focuses on the effects of high heating rates and different end-temperatures on two prior microstructures of a 50CrMo4 steel. Different heating devices, from a dilatometer up to a lab scale induction heating generator were used for the heat treatments, while microstructure was studied with a combination of high resolution techniques, such as Scanning and Transmission Electron Microscopy and 3D Atom Probe Tomography. Through detailed analysis of every single process step it could be shown that an inductive quench and tempered process leads to increased hardness and toughness properties compared to a conventional furnace heat treatment, if the process parameters are adapted favorably. This study focused on all process parameters of induction heat treatments and elucidates the influences of heating rates and temperatures on the resulting microstructure and mechanical properties. Fast austenitizing treatments with high heating rates (10-100K/s) might lead to insufficient time for homogenization and carbide dissolution during austenitization which results in higher transformation temperatures. Inhomogeneities within the austenitic matrix result in increased strain in the martensitic crystal structure after quenching. However, during tempering the increased strain within the martensitic matrix leads to an increased amount of nucleation sites for tempering carbides and to smaller tempering carbides and therefore beneficial hardness and toughness properties. This work contributes also to the knowledge of the influences of processing parameters on the microstructure evolution and mechanical properties, which can be helpful to set up processes with higher productivity but without deterioration of the material properties.

KW - Induktion

KW - schnelle Wärmenbehandlung

KW - Vergütungsprozess

KW - mechanische Eigenschaften

KW - Martensit

KW - fast heat tratment

KW - induction

KW - steel

KW - quench and temper

KW - mechanical properties

M3 - Doctoral Thesis

ER -