The Influence of Pretreatment on the Adhesion of Ceramic Coatings on Steel

Summary

Pretreatment of the substrate in the form of grit blasting is shown to exert a critical effect on coating adhesion. The adhesion of plasma sprayed alumina coatings increases linearly with the average roughness of the substrate and reaches a maximum at an optimum peak spacing. The optimum spacing is found to increase with increasing particle size of the feedstock powder. The underlying mechanism of this behaviour is shown to be related to the effect of the microgeometry of the substrate surface on the flow of the impacting molten particles. The optimum pretreatment provides a surface texture that suppresses splashing by dissipating the kinetic energy of the incoming droplets.