TY - BOOK

T1 - Interfacial damage of TiN coated high speed steels under a realistic spectrum of shear- and normal loads

AU - Gsellmann, Matthias

N1 - embargoed until 27-12-2026

PY - 2021

Y1 - 2021

N2 - The constantly increasing demands of the metal-cutting industry for a higher tool life at simultaneously increasing cutting speeds require a continuous improvement and further development of the materials used, for example tool steels. In order to withstand the loads imposed during metal cutting, tool steels are coated with a hard coating, which is deposited via physical vapour deposition. In order to ensure a high tool lifetime, a strong adhesion between the coating and the steel substrate is of great importance. Damage to the coating can lead to failure of the entire tool. For this reason, knowledge of the damage mechanisms of coating-substrate systems are essential. The aim of this work is to investigate the damage mechanisms occurring at the interface of TiN coated high speed steels (HSS) under realistic shear-compression loading. The damage in the lubricated and unlubricated condition as well as after a variation of the HSS chemistry was investigated using focused ion beam preparation of cross sectional samples studied by scanning electron microscopy. An influence of the MC and M6C primary carbides on the damage due to cyclic plastic deformation of the martensitic matrix and subsequently on the coating adhesion was observed. Using micromechanical tests on a specially developed sample geometry, a strength ranking between the TiN coating and the MC and M6C primary carbides as well as the martensitic matrix was established. By means of high-resolution transmission electron microscopy and ab-initio simulations, this interfacial strength ranking could subsequently be confirmed. Based on the results obtained, it can be concluded that damage of a TiN-coated HSS does not occur as a result of insufficient coating adhesion, since the interface strengths of the microstructural components are sufficiently high, but due to plastic deformation of the matrix on the one hand or as a result of fatigue damage on the other hand.

AB - The constantly increasing demands of the metal-cutting industry for a higher tool life at simultaneously increasing cutting speeds require a continuous improvement and further development of the materials used, for example tool steels. In order to withstand the loads imposed during metal cutting, tool steels are coated with a hard coating, which is deposited via physical vapour deposition. In order to ensure a high tool lifetime, a strong adhesion between the coating and the steel substrate is of great importance. Damage to the coating can lead to failure of the entire tool. For this reason, knowledge of the damage mechanisms of coating-substrate systems are essential. The aim of this work is to investigate the damage mechanisms occurring at the interface of TiN coated high speed steels (HSS) under realistic shear-compression loading. The damage in the lubricated and unlubricated condition as well as after a variation of the HSS chemistry was investigated using focused ion beam preparation of cross sectional samples studied by scanning electron microscopy. An influence of the MC and M6C primary carbides on the damage due to cyclic plastic deformation of the martensitic matrix and subsequently on the coating adhesion was observed. Using micromechanical tests on a specially developed sample geometry, a strength ranking between the TiN coating and the MC and M6C primary carbides as well as the martensitic matrix was established. By means of high-resolution transmission electron microscopy and ab-initio simulations, this interfacial strength ranking could subsequently be confirmed. Based on the results obtained, it can be concluded that damage of a TiN-coated HSS does not occur as a result of insufficient coating adhesion, since the interface strengths of the microstructural components are sufficiently high, but due to plastic deformation of the matrix on the one hand or as a result of fatigue damage on the other hand.

KW - TiN coating

KW - micromechanical testing

KW - inclined impact test

KW - cyclic plastic deformation

KW - FEM analysis

KW - DFT analysis

KW - TiN Beschichtung

KW - mikromechanischer Test

KW - Schrägschlagtest

KW - zyklische plastische Verformung

KW - FEM Analysen

KW - DFT Analysen

M3 - Doctoral Thesis

ER -