Characterization of BN/TiBN/TiN multilayer coatings prepared by pulsed dc plasma-enhanced chemical vapor deposition

BN/TiBN/TiN multilayer coatings were deposited on steel specimens by pulsed dc plasma-enhanced chemical vapor deposition (PECVD) using mass-production-type equipment. Using glow discharge optical emission spectroscopy, it was proven that the coatings exhibited a three-layered structure composed of BN/TiBN/TiN coatings. The cross section of the upper BN coating exhibited a dense structure, which was different from the columnar structures by those of the TiN and TiBN coatings. Analyses by X-ray diffraction or Raman spectroscopy demonstrated that the upper layer coating was hexagonal boron nitride (h-BN). X-ray photoelectron spectroscopy analyses of the upper layer coating demonstrated that BN compound was present. Observations performed by transmission electron microscope revealed that the upper BN coating was the onion structure and fibrous, and the coating was composed of particles about 10-20nm. The surface hardness of the BN/TiBN/TiN multilayer coatings was 4.5 GPa, which was lower than those of TiN and CrN coatings prepared by physical vapor deposition. The BN/TiBN/TiN multilayer coatings exhibited higher oxidation resistance and better tribological properties than the TiN and CrN coatings. Furthermore, they exhibited superior soldering and erosion resistance in a molten aluminum die-casting alloy in comparison with other specimens.