PHYSICAL VAPOR-DEPOSITION OF COMPLEX HARD COATINGS ON CERAMIC SUBSTRATES

Today there exists only a little information about hard coatings obtai ned 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 depo sited by reactive magnetron sputtering on silicon nitride (Si3N4), alu minium oxide (Al2O3) and Al2O3 + TiC ceramic. As a reference, coated h igh speed steel and cemented-carbide substrates have been used. Coatin g systems were complex hard materials of the Cr-Al-C-N and Ti-V-C-N sy stems. R.f. bias allowed the deposition of these coatings on electrica lly 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 determinat ion of the coating-substrate microstructure. Model wear tests gave inf ormation on the wear resistance of the coated ceramics, and annealing tests verified thermal stability.