The Influence of Layers Thickness on the Structure and Properties of Bilayer Multiperiod Coatings Based on Chromium Nitride and Nitrides of Transition Metals Ti and Mo

Abstract

The influence of the layers thickness of bilayer multi-period coatings of the CrNx/MoNx and CrNx/TiNx systems on their phase-structural state, substructure, stress-strain state and mechanical properties was studied using methods of precision structural analysis in combination with computer simulation of implantation processes during particle deposition. It is established that a two-phase structure of CrN and -Mo2N phases of the structural type NaCl is formed in the multi-period coatings of the CrNx/MoNx system with a nanometer thickness of the layers. Because of the small difference in periods (less than 0.5 %) for Λ  20 nm, the layers form a coherent interlayer interface. The use of small Ub -20 V during deposition makes it possible to avoid significant mixing at interlayer (interphase) boundaries even at the smallest Λ  10 nm. Nitride layers formed under conditions of vacuum arc deposition are under the action of compressive stresses. In the СrNх/TiNх system, because of the relatively large discrepancy between periods (more than 2.5 %), during the formation of the same structural components in the layers (CrN and TiN phases of the structural type NaCl), the epitaxial growth with period adjusting does not occur, even for the smallest Λ  10 nm. The action of the deformation factor at the interphase boundary allows achieving an ultrahard state (with a hardness of about 50 GPa), which causes a relatively low friction coefficient. The obtained results on the formation of phase-structural states with the nanoscale thickness of layers of multi-period nitride coatings are explained from the position of minimization of surface energy and deformation energy.

Microstructures and Properties of TiSiN/TaVN Nanomultilayers with Various V Contents

“…It shows that the nanomultilayer with 15.at% V content has better resistance to plastic deformation than the other nanomultilayers. The theories of hardness increasing of nanomultilayers have modulus difference theory [9] and alternating stress field theory [34]. TiSiN layer and TaVN layer grow in a coherent epitaxial structure.…”