Suspension Plasma-Sprayed Alumina Coating Structures: Operating Parameters Versus Coating Architecture

Abstract

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

Solution and Suspension Plasma Spraying of Nanostructure Coatings

“…To study the spray bead manufacturing mechanisms, Tingaud et al (2008) made a suspension of alumina of angular single mono-crystalline α-Al 2 O 3 (P152 SB, Alcan, Saint-Jean de Maurienne, France) of d 50 = 0.5 µm dispersed in pure ethanol with an electro-steric dispersant. The powder mass fraction in suspension was 10 wt%.…”

“…Al 2 O 3 suspension plasma-sprayed coating microstructures for two particle mass loads (5 and 10 wt%) and three spray distances (30, 40, 50 mm). Spray conditions are depicted in Figure 32 caption Tingaud et al (2008).…”

Thermal Plasma Processes for Production of Hollow Spherical Powders: Theory and Experiment

“…In several recent years an active interest has been shown to suspension plasma spraying (SPS), a process in which a liquid containing suspended nano-and submicrometer particles of spray material is injected under pressure into a plasma flow [22][23][24][25].…”

Effective Injection of Ceramics Nanoparticle Pastes into Plasma Spray for Speedy Layer Formation

“…Because the nanoparticles in the suspensions occur in 10 vol%, the deposition rates are about several micrometers per second, which are lower than the results observed with conventional plasma and gas flame thermal spraying techniques [1][2][3] . Thermal nanoparticles spraying method has been developed as a novel coating technique to create fine ceramic layers without structural defects at higher deposition rates on the free surfaces of practical alloy substrates 4,5) .…”