Thermal stability and mechanical properties of amorphous coatings in the Ti-B-Si-Al-N system grown by cathodic arc evaporation from TiB2, Ti33Al67, and Ti85Si15 cathodes

Abstract

Ti-B-Si-Al-N coatings were grown on cemented carbide substrates in an industrial scale cathodic arc evaporation system using Ti33Al67, Ti85Si15, and TiB2 cathodes in a reactive N2 atmosphere. The microstructure of the as-deposited coatings changes from nanocrystalline to amorphous with addition of (B + Si + Al), or high amounts of (B + Si) to TiN. In the as-deposited state, the 4 μm-thick amorphous coatings are dense and homogeneous, beside slight compositional modulation with Ti-rich layers induced by rotation of the substrate holder fixture during deposition, and have unusually few macroparticles. Annealing at temperatures ranging from 700 to 1100 °C results in that the coatings crystallize by clustering of TiN grains. The hardness of as-deposited amorphous coatings is 17–18 GPa, and increases to 21 GPa following annealing at 800 °C. At annealing temperatures of 1000 °C and above the hardness decreases due to interdiffusion of Co from the substrate to the coating.