Preparation and tribological properties of plasma sprayed nano and micro-structure alumina-reinforced CuAl composite coatings

Nano-structured alumina (n-Al2O3) powders prepared by spray drying granulation and micro-structured alumina (m-Al2O3) powders by fused-crushed method were used to fabricate Al2O3 reinforced CuAl coatings. The microstructure and phase composition of the coatings were analyzed, and their tribological properties were investigated in comparison with those of the CuAl coating. In both CuAl/n-Al2O3 and CuAl/m-Al2O3 coatings, the reinforcing Al2O3 exists as well-flattened splats, and shows good interfacial compatibility with the bronze matrix. The alumina existed as amorphous and γ-Al2O3 phase in the CuAl/m-Al2O3 composite coating, while α-Al2O3 phase was contained in the CuAl/n-Al2O3 coating. Although the CuAl/n-Al2O3 composite coating gives a highest friction coefficient at all loads, it possesses superior wear-resistance as compared with the CuAl/m-Al2O3 coating and pure CuAl coating.