Research On Plasma Sprayed SiC/Al₂O₃ Nanocomposite Ceramic Coating

In this paper, A1(OH)3 sol and Polyvinvl Alcohol were used as binder, nano-micrometer, nano-nano SiC/Al2O3 composite powder was prepared through wrapping and spraying granulation method. The content of n-SiC and the sinter temperature of composite powder greatly influence the coatings' microstructrural uniform. The preparation route of nano-micrometer n-SiC/Al2O3 composite powder were optimized by comparative investigation, and the nanocomposite SiC/Al2O3 ceramic coating was plasma sprayed. By experiments, conclusions were drawn as following:1 The technology of nano-micrometer n-SiC/Al2O3 wrapping composite powder was determined, prepared using A1(OH)3 sol as binder:Preparation of Al(OH)3 sol→Padded m-Al2O3→stirred→added n-SiC particle →filtered→dried→sintered at 800℃→ground→sifted2 The results indicate that, for the nano-micrometer n-SiC/Al2O3 composite powder, using A1(OH)3 sol as binder, SiC would decompose when spraying power is higher than 40kW; the nano-micrometer n-SiC/Al2O3 composite coating could be obtained when the power below 40kW, and n-SiC particles were located within m-Al2O3 grains and grain boundary.3, When 3Vol% n-SiC particle were added, the composite coating is quite dense ,with low porosity, and the hardness was greatly increased ,exhibiting relatively higher wear resistance than other composite coating with other n-SiC particle contents.4, The formation mechanism of the n-SiC particles in the ceramic coating prepared by the nano-micrometer n-SiC/Al2O3 composite powder located within m-Al2O3 grains is revealed:m-Al2O3 would be well melted during spraying and form droplet, the n-SiC particles existing on the surface of droplet, then the particle enter the droplet when it is impacted and flattened on the substrate.5 The best technical parameters of nano-nano SiC/Al2O3 composite powder prepared through spray granulation method: solids content 25wt%;binder content 2.3wt%;dryingtemperature 510~530℃ ;sinter temperature 1200℃ ; contract air pressure 0.3 + 0.05MPa.6 , The formation of nano-nano SiC/Al2O3 composite ceramic coating: The heating difference of the powder in-outer layer during spraying results in that the inner nanoparticles are only partially melted, without growing into larger grain, a lot of nanoparticle agglomerates with sintered shape were detected in the coating.