Microanalysis of the Al 2O 3TiC interface in aluminacoated cemented carbides by Auger electron and glow discharge emission spectroscopies

Abstract

The Al 2O 3TiC interface was studied by Auger electron spectroscopy (AES) and glow discharge emission spectroscopy (GDES) depth profiling on cemented carbide inserts precoated by chemical vapour depositiom (CVD) with a thick layer of TiC and then coated with an alumina film 1 μm thick by a physical vapour deposition (PVD) or a CVD technique. GDES depth profiling based on argon ion sputtering was found to be inapplicable because of the insulating character of alumina, whereas it leads to good results for conducting hard coatings ( e.g.TiN). In contrast, AES depth profiling appears to be applicable to the analysis of alumina coatings provided that the sample has first been mechanically thinned and then coated with a thin film of gold or platinum. The interactions between alumina and TiC that take place during deposition, based on interdiffusion phenomena, are very limited for PVD coatings performed at about 300°C but much more important for CVD coatings obtained at about 1050°C. Post-deposition annealing further increases the extension of the interaction zone. Such phenomena are thought to play an important role in coating-substrate adherence.