European Ceramic Society (ECerS), event, 10-14 July 2022, Krakow, (oral accepted)
D. Chatelain1, A. Denoirjean1, V. Guipont², F. Rossignol1 and N.Tessier-Doyen1
1 Institut de Recherche sur les Céramiques (IRCER), UMR CNRS 7315 ; 12 rue Atlantis, 87068 LIMOGES, France
² Centre des Matériaux, MINES Paris Tech, UMR CNRS 7633 ; 63-65 rue Henri-Auguste Desbruyères, 91000 EVRY, France
Abstract
Cold spray is based on the acceleration at a supersonic velocity (up to 1200 m.s-1) of unmelted powder particles through a de Laval nozzle by a high-pressure gas (e.g. N2). As the powder is not molten in the gas, the deposit is mostly generated by the powder plastic deformation and/or brittle fragmentation and its mechanical anchorage when impacting the substrate at high kinetic energy.
Up to date, cold spray has been mostly dedicated to ductile materials (i.e. metals). However, cold spray of brittle materials (i.e. ceramics) has recently gained attention. In the specific case of ceramics, the challenge consists mostly in controlling the powder fragmentation at the impact to optimize the coating quality (i.e. low porosity and good mechanical adhesion) and its construction rate.
In thermal spraying, usually axial injection is chosen at the expense of the radial one. Indeed, the particles injection in the stream is more homogeneous and chance of clogging are lower, especially with ceramics powders. However, in Low Pressure Cold Spray, axial injection is not possible, since it appears in the diverging part of the nozzle. Thus, the idea of this work is to create a nozzle with an angle, in order to limit the clogging and to homogenize the stream.
This angle permit at the same time to limit the powder fragmentation inside the nozzle, to increase the precision in the velocity measurement, and to improve the deposition efficiency.
