Thermal spray coatings of highly reinforced aluminium matrix composites with sol–gel silica coated SiC particles

Low porosity coatings made of aluminium matrix composites reinforced with SiC particles were fabricated by a thermal spray method. The initial spray material used was a mixture of aluminium powder and SiC particles which were directly fed in the thermal spray gun flame without any previous sintering. Sol–gel silica coatings with different structural characteristics were deposited on the SiC particles before mixing with aluminium powder to increase the wettability of reinforcement by molten aluminium during the spray while avoiding the appearance of any degrading reaction between aluminium and SiC particles. The thermal spray coatings were manufactured with different reinforcement degrees from 4 vol.% to 47 vol.% SiC using mixtures of sol–gel coated SiC particles in the 20% to 70% range. Porosity was in most cases below 1%. The relevance of using sol–gel coatings on reinforcement particles and of the sol–gel structure is analysed.