Production and characterization of Cr2O3-Ag nanostructured composite powders in plasma spraying process

In plasma sprayed nanostructured composite coatings with ceramic matrix, the feedstock must consist of nanoparticles of appropriate specifications. In this research, the procedure for production of Cr2O3-Ag agglomerated nanostructured composite powder to produce comosite coatings has been investigated. Nanopowders of Cr2O3 with 0, 2, 5, and 10 volume percentages of silver were dispersed to obtain a homogeneous aqueous dispersion appropriate for spray drying process. In the second stage, Cr2O3-Ag composite powders were produced by agglomeration process. The nanostructured composite powders were, then, used in the atmospheric plasma spray (APS) process to deposit a series of composite coatings for evaluation. The composite powders, with a granulated morphology, had uniform distribution of silver in a ceramic matrix and the coatings were composed of nanoparticles and particles of nano-sized crystallites. Experimental results indicated that presence of nanoparticle zones within the microstructure led to non uniform porosities formed between splats and these zones. Furthermore, use of nanopowders in the feedstock caused a reduction in lamellae thickness of plasma sprayed coatings.