Papers by Author: Francois Borit

Abstract: Basically, thermal spray and laser processing can be considered as half brothers since they show many common features due to the use of a (more or less) high-energy source for both. Their combination can therefore be very fruitful and prominent to achieve coatings, which results in their most recent and advanced applications. In the materials processing development story, the laser will thus have moved from cutting to coating. This keynote presentation focuses on the recently-developed coupling of laser processing to cold spray). In this dual process, a cold spray gun is combined to a laser head in a single device, e.g. on a robot. Series of coating experiments using various laser irradiation conditions, primarily pulse frequency, were carried out for Al-based and Ni-based alloys. Laser pre-treatment of the substrate just prior to cold spray, was shown to be beneficial for adhesion of cold-sprayed coatings. Adhesion improvement was exhibited and studied from LASATesting (LASAT for “LAser Shock Adhesion Test”). Incidentally, through LASAT also, the role of lasers in the development of thermally-sprayed coatings can be considered as major. Results are discussed in the light of a TEM (Transmission Electron Microscope) study of the coating-substrate interface with and without laser pre-treatment.

Abstract: 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.