Hardness recovery of ceramic coated aluminium matrix composites using thermal-shock resistant sol–gel silica coatings

Sol–gel silica coatings increase wear and corrosion resistance of aluminium matrix composites, but a heat treatment stage at temperatures as high as 500 °C is usually required to consolidate the ceramic coating. Under these thermal conditions, sol–gel ceramic coatings tend to crack and the aluminium matrix hardness strongly reduces. Present paper describes how the combination of a certain sol–gel procedure accompanied with quenching treatment in silicone oil allows recovering most of the hardness of the substrate, while keeping undamaged the sol–gel silica coating deposited.