Microstructural Study of Copper and Copper/Alumina Composite Coatings Produced by Cold Spray Process

Cold spraying is a novel coating method, by which many composites have been successfully sprayed. The objective of this study was to thoroughly characterize the microstructure of copper as well as copper/alumina composite coatings obtained using this technique. Composite coatings which differed to the percentage of Al2O3 in the initial powder blend as well as the Al2O3 particle size were studied. Coatings presented Ra of the order of 6-8 μm, with the copper coating having the highest value. Using optical microscopy the deformation of the copper particles of the cross sections was evident. Thickness ranged from 170 to 450 μm for the different coatings. The surfaces and the cross sections of the coatings were studied by means of scanning electron microscopy. Craters and Al2O3 particles that were embedded in the copper particles were observed. The XRD analysis of the powders and the respective coatings presented no differences.