Papers by Author: Christian Moreau

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: Intermediate temperature SOFC components, such as dense, nanostructured SDC electrolytes (samarium doped ceria) and porous anode sublayers were fabricated by suspension plasma spraying using an axial feed dc plasma torch. The liquid carrier employed in this approach allowed for controlled injection of much finer particles than in conventional thermal spraying, leading to thin coatings with a refined microstructure. Dense, thin (<10(m) and non-fractured electrolytes were created. Various processing routes for SOFC half-cells, using tape-cased, plasmasprayed and suspension-sprayed anodes, were explored. Loss of integrity and non-continuous coverage of the anode constituted the principal difficulties in the subsequent electrolyte deposition. The role of suspension feedstock particle size is discussed. Amongst various schemes investigated, a processing route that employs sequential suspension plasma spraying steps for both the electrolyte and the anode, using relatively large primary particles in the feedstock, constituted the most promising approach.