Plasma densification of agglomerated Cr 2 O 3 powder for thermal spray coating

Double plasma flame treatments were carried out on spray dried Cr₂O₃ agglomerated powders to increase their apparent density. The powders that were subjected to the first densification treatment didn't show the entirely melted state, and were fully melted only after the second plasma treatment. Plasma densification resulted in powder size decreasing as well as apparent density of particles and also resulted in the fluidity increasing due to the powder melting and surface smoothing effects. However, some parts of the particles after the second treatment showed a hollowed structure, especially for a particle size above 30 µm. The influence of the thermal conductivity of powder and the gas pressure within aggregates exposed to the plasma flame in the particle densification process was discussed in detail. The powder density strongly influenced the structure of plasma sprayed coatings. The dense coatings with high hardness and high bond strength was achieved in the coatings produced from Cr₂O₃ powders after plasma densification.