METAL-CERAMIC INTERFACES IN LASER COATED ALUMINUM-ALLOYS

A novel process was developed to firmly coat an aluminium alloy, Al606 1, with alpha-Al2O3 by means of laser processing. In this approach a m ixture of SiO2 and Al powder was used to inject in the laser melted su rface of aluminium. A reaction product alpha-Al2O3 layer of a thicknes s of 100 mum was created which was well bonded to the aluminium surfac e. Various interfaces, Al/alpha-Al2O3, Al/mullite and alpha-Al2O3/mull ite, were studied by conventional transmission electron microscopy (CT EM) and high resolution electron microscope (HREM). It turns out that the presence of the Al/mullite interface may be essential to form a we ll bonded oxide layer and the high Si-content alpha-Al2O3 intermediate layer may be wetted better by liquid Al. Investigations of the interf ace structures and wetting phenomena during laser processing are prese nted and a simple correlation between wetting phenomena and interface strength is derived.