Effect of Cr doping on interface properties of DLC/CrN composite coatings: First-principles study

Abstract

Diamond-like carbon (DLC) is one of the most studied and promising coating materials, but many of the bonding mechanisms involved in interfaces between transition layer and DLC coating are not fully understood. Here, the effect of Cr doping in DLC coating on the adhesion strength of DLC/CrN interface was investigated by using first principles method. The thermodynamic stability of CrC interface is higher and the bonding strength is larger than that of NC one. Meanwhile, the adhesion work of Cr doped interface is larger that of clean interface. In addition, the segregation heat is positive value when small amounts of Cr atoms are introduced into the interface, which indicates Cr atoms are easy to segregate towards the interface. The differential charge density and bader charge indicate that for the doped interface Cr-CCr(1), the transfer of electrons between the interfaces is inhibited by doping Cr atoms. For the doped interface N-CCr(1), the doping Cr atoms makes the first layer of N atoms and the second layer of Cr atoms on the CrN surface participate in charge transfer. Therefore, the calculation results can provide a good theoretical basis for improving the performance of DLC and broadening its application field.