Physical vapour deposition of complex hard coatings on ceramic substrates

Abstract

Today there exists only a little information about hard coatings obtained by physical vapour deposition (PVD) on ceramic substrates. The aim of the PVD coating on ceramic substrates is a further improvement of the material properties, e.g. wear resistance. Coatings have been deposited by reactive magnetron sputtering on silicon nitride (Si 3N 4), aluminium oxide (Al 2O 3) and Al 2O 3 + TiC ceramic. As a reference, coated high speed steel and cemented-carbide substrates have been used. Coating systems were complex hard materials of the Cr-Al-C-N and Ti-V-C-N systems. R.f. bias allowed the deposition of these coatings on electrically insulating substrates. Mechanical characterization of the coatings has been made by determination of hardness, critical load and impact load (coating impact test). Scanning electron microscopy investigation of the rupture structure and X-ray diffraction allowed the determination of the coating-substrate microstructure. Model wear tests gave information on the wear resistance of the coated ceramics, and annealing tests verified thermal stability.