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This paper examines how the grit blasting process influences the surface roughness of different substrates, the grit residue, and the grit erosion. The influence of grit blasting conditions on induced substrate residual stresses is also discussed. Aluminum alloy, cast iron, and hard steel were blasted with white alumina grits of 0.5, 1, and 1.4 mm mean diameters. Grit blasting was performed using either a suctiontype or a pressure-type machine equipped with straight nozzles made of B4C. The influence of the following parameters was studied: grit blasting distance (56 to 200 mm), blasting time (3 to 30 s), angle between nozzle and blasted surface (30 ~ 60 ~ 90~ and blasting pressure (0.2 to 0.7 MPa). The roughness of the substrate was characterized either by using a perthometer or by image analysis. The grit residue remaining at the blasted surface was evaluated after cleaning by image analysis. The residual stresses induced by grit blasting were determined by using the incremental hole drilling method and by measuring the deflection of grit-blasted beams. Grit size was determined to be the most important influence on roughness. The average values of Ra andRt and the percentage of grit residue increased with grit size as well as the depth of the plastic zone under the substrate. An increase of the pressure slightly increased the values of Ra and Rt but also promoted grit breakdown and grit residue.A blasting time of 3 to 6 s was sufficient to obtain the highest roughness and limit the grit breakdown. The residual stresses generated under the blasted surface were compressive, and the depth of the affected zone depended on the grit diameter, the blasting pressure, and the Young's modulus of the substrate. Moreover, the maximum residual stress was reached at the limit of the plastic zone (i.e., several tenths of a millimeter below the substrate surface).

International audienceSuspension plasma spraying (SPS) is able to process sub-micrometric-sized feedstock particles and permits the deposition of layers thinner (from 5 to 50 lm) than those resulting from conventional atmospheric plasma spraying (APS). SPS consists in mechanically injecting within the plasma flow a liquid suspension of particles of average diameter varying between 0.02 and 1 lm, average values. Upon penetration within the DC plasma jet, two phenomena occur sequentially: droplet fragmentation and evaporation. Particles are then processed by the plasma flow prior their impact, spreading and solidification upon the surface to be covered. Depending upon the selection of operating parameters, among which plasma power parameters (operating mode, enthalpy, spray distance, etc.), suspension properties (particle size distribution, powder mass percentage, viscosity, etc.), and substrate characteristics (topology, temperature, etc.), different coating architectures can be manufactured, from dense to porous layers. Nevertheless, the coupling between the parameters controlling the coating microstructure and properties are not yet fully identified. The aim of this study is to further understand the influence of parameters controlling the manufacturing mechanisms of SPS alumina coatings, particularly the spray beads influence

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International audienceSolution Precursor Plasma Spraying (SPPS) is a thermal spray process where a feedstock solution is heated and pyrolized to form fine (i.e., 1000 nm) molten particles that deposit onto a substrate to form a layer. The benefits of implementing the SPPS process include, among others: (i) the possibility to create unique microstructures at nanometer scale without the injection feeding problems usually associated to powder feeders and delivery cables and (ii) rapid exploration of novel precursor compositions. In this study, preparation and characterization of porous anode layers with homogeneous Nickel distribution and nanometer sized microstructure are considered for solid oxide fuel cell (SOFC) application. Once the solution is injected, the droplets go through several chemical and physical changes and impact the substrate in different states, from fully molten one to unpyrolized one. The effects of some spray parameters, such as the spray distance and the plasma flow mass enthalpy, on the layer architecture and composition were investigated. The results show that dense or porous layers can be manufactured depending on the operating parameters

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