Impact of Al and Cr alloying of TiN‐based PVD coatings on its cutting performance

Abstract

AbstractThe life of the cutting tools with TiN‐based coatings has been evaluated under turning and end milling. TiAlN and two compositions of TiAlCrN (25:65:10 and 10:70:20) coatings were investigated. The microhardness and the microhardness dissipation parameter of TiAlN and TiAlCrN coatings were measured. The energy band structure of the TiN‐based system has been calculated using EELFS data on surface atomic structure by self‐consistent density functional methods (ZINDO1). It was shown that the addition of Al to the TiN coating significantly reduce the inhomogenity of the electron density distribution within the volume of the molecules and a reduction in the chemical reactivity of the TiAlN coating. The addition of chromium to the TiN‐based nitrides also changes their electron structure decreasing the ion‐covalent character of the interatomic bonds of the crystal lattice while the hybridization of the d π‐electronic states responsible for the metallic atom bonds within the crystal lattice. The probability of the electron transfer to the condition zone also increases. All these features explain the phenomenon of the plasticity improvement in the TiN‐based compounds alloyed with Cr. Simultaneous addition of Cr and Al in the complex TiN‐based nitride weakens the long‐range bonds within the crystal lattice and reduces the polarity of these bonds down. This results in the enhancement of the plasticity of these compounds and improves the life of coated end‐mill cutters. Copyright © 2006 John Wiley & Sons, Ltd.