Properties and microstructure of Al-11Si/SiCp composite coatings fabricated by thermal spray

Thermal spraying has been used to coat 6082-T6 aluminium alloy with aluminium matrix composites. Mixtures of Al-11Si powder and 20 vol.% SiC and 40 vol.% SiC particles in the powder feeder were used as spraying material. In some conditions, SiC particles were coated with a sol-gel silica coating, which acts as an active barrier enhancing the wettability of the reinforcement by molten aluminium reducing the porosity of the composite coatings and inhibiting the formation of aluminium carbide. Coatings with a reinforcement volume fraction up to 17 vol.% (for 20 vol.% SiC in feeder) and 27 vol.% (for 40 vol.% SiC in feeder) were obtained with porosities below 1.0%. In all cases, the incorporation of sol-gel silica coatings on SiC particles reduced the porosity and increased the reinforcement volume fraction and the hardness of the coatings. The role played by the different spraying parameters has been also studied.