Cathodic arc deposition of (Al,Cr)2O3: Macroparticles and cathode surface modifications

The present work investigates the microstructure and chemical composition of macroparticles incorporated in arc evaporated (Al,Cr)2O3 coatings. According to scanning and transmission electron microscopy analysis, two different types of macroparticles with a distinct difference in their shape and a noticeable variation in their chemical composition, i.e. the Al/Cr ratio, can be distinguished. In addition, the transformations on the surface of the corresponding Al–Cr compound cathodes during the evaporation process in O2 atmosphere are studied by scanning electron microscopy and X-ray diffraction. Beside the virgin cathode material, a reaction layer consisting of various intermetallic AlxCry phases with a fine-grained morphology and pillar-shaped Al2O3 islands was found. Correlations between the origin of the macroparticles and the observed modifications at the surface of the Al–Cr cathode are discussed.