Cold gas spraying is a solid-state deposition process developed for metallic powders as feedstock materials. For ceramic materials; such low temperature-high velocity kinetic process is still questionable but could have interesting advantages. In the CERASOL project (ANR-19-CE08-0009); the nature and the architecture of porous ceramic powders involving agglomerated sub-micrometric grains are investigated. To that purpose; three oxide ceramics powders (alumina; zirconia and yttria) have been prepared for cold spray. These powders were analyzed in order to assess their architecture (composition; particle size; porosity; density; crystallite sizes…). Preliminary cold spray experiments were carried out implementing velocities measurements for various stand-off distances and spraying of coupons with line experiments. The characteristics of the deposited layers have been examined by SEM and XRD in order to discuss the role of the powder architecture on the impact behavior of the nanostructured agglomerated particles. The role of the gas stream that affects the kinetic and the trajectory of the particles are also discussed.

Most of ductile metals can be deposited by cold spray (CS). For brittle ceramic, such solid-state deposition process is still questionable, but some recent work on Ti02 or hydroxyapatite powders have shown that micrometric ceramic powder could be deposited by CS. In this work, it is claimed that the nature and the porous architecture of a ceramic powder with agglomerated ultra-fine grains play an important role on the impact behaviour. The aim of this work is to investigate the deformation behaviour of ceramic agglomerated powders under high velocity impact. Two different powders, respectively 3YSZ and Y2O3, were selected in order to study their architectures (particle size, porosity, density, crystallite size, etc.). Cold spray “splats” experiments, with various spraying distances to vary the particles velocities upon impact, were carried out to observe the deformation and fragmentation. In case of Y2O3, cold spray with dynamic vacuum surrounding atmosphere up to 3kPa were also prepared to evaluate the role of the atmosphere on the resulting impact. In parallel, in situ SEM micro-compression tests at 10−2 s−1 on cross-sectioned 3YSZ particles involving flat-punch nano-indentation and micropillar compression were performed. By modelling the compression tests, the aim is to identify a Drücker-Prager behaviour law suitable for an agglomerated ceramic powder under quasi-static compression. Such deformation behaviour could help to better understand the compaction behaviour of agglomerated powders.