Bonding Characteristics of Cold Sprayed Copper Coating on Alumina Coated Q235 Steel Substrate

Abstract

Cold spraying metallic coatings on ceramics (Ceramics Metallizing) are widely concerned in electrical industry due to its high density, low oxidation and high electrical conductivity. However, the bonding reliability of cold spraying coating on ceramics is usually considered to be poor since the metal particles don’t experience melting. The present paper is to exam the bonding quality of a cold spraying copper coating on a thermal sprayed alumina layer influenced by ceramics roughness and copper particle hardness. Pure copper coatings were successfully deposited on Al₂O₃ coated Q235 steel substrate with different roughness by cold spraying at 260 ℃ and 1.6 MPa using different hardness pure copper powders. The bonding quality and characteristics were studied by analyzing the surface, the cross-sectional microstructure of the coating and its interface after pull-off test. The results indicate that the high bonding quality (ranging from 8.26 MPa to 11.35 MPa) between copper coating and Al₂O₃ layer attributes to both metallurgical and interlock effect, which is mainly influenced by the hardness of the copper powders instead of Al₂O₃ surface roughness. The soft character of the pure copper powder makes it ready for deformation, subsequently interlocks with Al₂O₃, fills into the pores more completely, which increases the bonding quality between the copper coating and the Al₂O₃ layer.