Plasma densification of agglomerated Cr2O3 powder for thermal spray coating

Double plasma flame treatments were carried out on spray dried Cr2O3 agglom erated powders to increase their apparent density. The powders that were su bjected to the first densification treatment didn't show the entirely melte d state, and were fully melted only after the second plasma treatment. Plas ma densification resulted in powder size decreasing as well as apparent den sity of particles and also resulted in the fluidity increasing due to the p owder melting and surface smoothing effects. However, some parts of the par ticles after the second treatment showed a hollowed structure, especially f or a particle size above 30 mum. The influence of the thermal conductivity of powder and the gas pressure within aggregates exposed to the plasma flam e 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 th e coatings produced from Cr2O3 powders after plasma densification. (C) 2001 IoM Communications Ltd.