The effect of boron additions on the tribological behaviour of TiN coatings produced by electron-beam evaporative PVD

Abstract

TiN coatings containing small amounts of boron were synthesized by electron beam evaporating a Ti-B alloy material from a single crucible source into a plasma comprising Ar or an Ar/N2 mixture at a substrate temperature of 450°C. The influence of 2 at.% B on the structural, mechanical and tribological properties of electron-beam (EB)PVD coatings is described. All coatings, consisting of different phases according to their location in the ternary Ti-B-N phase diagram, showed dense structures. Glancing angle X-ray diffraction spectra revealed only the presence of the Ti and TiN phases, respectively, for coatings deposited in either Ar or Ar/N2 gas mixtures. The hardness and elastic modulus of the Ti(B)N coatings increased linearly with increasing nitrogen content. Slightly overstoichiometric Ti(B)N coatings (Ti0.44B0.02N0.54) showed wear rates in reciprocating sliding wear tests against cemented tungsten carbide balls two orders of magnitude lower compared to a similar commercial EBPVD TiN coating. TiN coatings containing small amounts of boron were synthesized by electron beam evaporating a Ti-B alloy material from a single crucible source into a plasma comprising Ar or an Ar/N2 mixture at a substrate temperature of 450 °C. The influence of 2 at.% B on the structural, mechanical and tribological properties of electron-beam (EB)PVD coatings is described. All coatings, consisting of different phases according to their location in the ternary Ti-B-N phase diagram, showed dense structures. Glancing angle X-ray diffraction spectra revealed only the presence of the Ti and TiN phases, respectively, for coatings deposited in either Ar or Ar/N2 gas mixtures. The hardness and elastic modulus of the Ti(B)N coatings increased linearly with increasing nitrogen content. Slightly overstoichiometric Ti(B)N coatings (Ti0.44B0.02N0.54) showed wear rates in reciprocating sliding wear tests against cemented tungsten carbide balls two orders of magnitude lower compared to a similar commercial EBPVD TiN coating.