Effects of B and C elements on microstructure, mechanical and tribological properties of TiN coating deposited by PACVD

Abstract

In recent years, hard coatings have gained various industrial applications due to their excellent properties. This research describes the effects of adding B, C and both elements on the microstructure, mechanical and tribological properties of TiN film synthesized by PACVD. The results indicate that incorporating boron and carbon into TiN results in the creation of a nanocomposite microstructure, where amorphous phases surround nano-crystals of TiN, h-BN, and TiB₂. The existence of carbon in the TiCN and TiBCN coatings manifests as DLC and amorphous carbon. The use of BBr₃ and CH₄ for depositing TiBCN coatings reduces the intensity of plasma formed surrounding the samples and increases the etching rate, resulting in a thickness reduction from 2.16 to 0.28 μm. The introduction of boron and carbon into the TiN coating enhances its hardness from 16.6 to 30 GPa, attributed to the formation of nanocomposite microstructures. TiBCN coating exhibits an indentation toughness value of 1.52 ± 0.2 MPa.m^0.5, the highest among the deposited coatings. The addition of carbon to both TiN and TiBN coatings reduces their coefficients of friction, decreasing from approximately 0.55 and 0.4, respectively, to about 0.3. This reduction is attributed to the creation of lubricating compounds like amorphous carbon and DLC.