MICROSTRUCTURE AND INTERFACES OF A REACTION COATING ON ALUMINUM-ALLOYS BY LASER PROCESSING

This paper reports an approach to coat a ceramic layer on aluminium al loys by means of chemical reaction. The reaction product of Al2O3, lay er of 100 mu m in thickness has been formed using a powder mixture of silicon oxide and aluminium by laser processing. It turns out that the large amount of heat from the exothermic reaction has a predominate e ffects on the formation of the oxide layer. Further, the negative free energy of the reaction may promote the metal/oxide wetting. The micro -hardness and wear tests proved that the oxide layer is hard and stron g. A mullite intermediate layer between aluminium and oxide have been identified by TEM. The atomic structure and defects of the reaction la yer have been imaged at high resolution electron microscope.