Phase composition, microstructure and mechanical properties of CVD Ti-B-N coatings deposited at different temperatures guided by thermodynamic calculations

TiBN coatings, as materials with broad potential applications, have received much attention in surface engineering in recent years. Within this work, the chemical vapor deposition (CVD) phase diagrams of TiBxNy coatings were calculated and the effects of deposition temperature (830-920 °C) on the microstructure, phase composition and mechanical properties of CVD TiBxNy coatings were investigated. The TiB0.61N0.84 and TiB0.61N0.81 coatings deposited at 830 and 860 °C have a particle-like surface, the TiB0.56N0.88 and TiB0.55N0.92 coatings deposited at 890 and 920 °C exhibit needle-like characteristic. XPS and TEM results indicate that TiBxNy coatings consist of nanocrystalline TiN and TiB2 embedded in amorphous TiB and BN matrix. The TiB0.61N0.84 coating exhibits the highest hardness of 40.7 GPa. The hardness of the coatings decreases as the deposition temperature increases. The presently developed approach of thermodynamic calculations and key experiments is equally valid for the efficient deposition of other CVD coatings.