Effect of Spherical Alumina on Cold Sprayed Aluminum-Alumina Cermet Coatings

The effect of spherical alumina content on the deposition efficiency and coatings mechanical properties are investigated in the cold spray deposition of aluminum-alumina cermets. The deposition of aluminum mixed with spherical alumina was studied and compared for six different feedstock powder compositions. Previous investigations have shown that the addition of angular alumina particles in the feedstock powder might increase in deposition efficiency for low alumina content. This effect was investigated with spherical alumina showing very little ceramic retention compared to the ones sprayed with angular alumina. These results have a direct impact on the mechanical properties and wear resistance of the coatings. Hardness showed an increase when alumina particles were added, however, this increase in hardness could not be directly related with the presence of alumina particles in the coating. Adhesion strength of coatings significantly increases with the addition of spherical in the feedstock powder, reaching the glue adhesion limit with coatings sprayed with 40wt.% alumina. It was determined that these increment in hardness and adhesion might be related to a high amount of plastic deformation in coatings sprayed with spherical alumina.