Al/SiC composite coatings of steels by thermal spraying

Thermal spraying has been used to coat carbon steels (F112) and austenitic stainless steels (AISI 304) with aluminium matrix composites. Mixtures of aluminium powder and SiC particles were used as spraying material. A sol–gel silica coating was laid on SiC particles to reduce the porosity of the composite coatings and to inhibit the formation of aluminium carbide. The sol–gel silica coating acts as an active barrier enhancing the wettability of the reinforcement by molten aluminium. Coatings with a reinforcement volume fraction up to 30 vol.% were obtained with porosities of about 1.0 vol.%. The incorporation of sol–gel silica coated SiC particles reduces the coefficient of thermal expansion of the composite coating and enhances its adhesion to the substrates more than when uncoated SiC particles were used.