Influence of particulate morphology on microstructure and tribological properties of cold sprayed A380/Al2O3 composite coatings

In this study, three kinds of A380/Al2O3composite coatings were prepared by cold spray(CS) using spherical, irregular and spherical + irregular shaped Al2O3particulates separately mixed in the original A380 alloy powders. The influence of Al2O3particulates’ morphology on the microstructural characteristics(i.e.retention of Al2O3content in coatings, coating/matrix interfacial bonding, pore size distribution and morphology etc.) and wear performance of the coatings was investigated by scanning electron microscopy(SEM), X-ray computed tomography(XCT) and 3-D optical profilometry. Results indicated that the spherical Al2O3shows obvious tamping effect during deposition process. As a result, the interface showed a wavy shape while the matrix and particulates were mechanical interlocked with much improved adhesion. In addition, the porosity of the coating was minimized and the pores exhibited curved spherical structure with reduced dimensions. The irregular Al2O3particles predominantly displayed the embedding effect together with fragmentation of Al2O3particulates. Consequently, poor coating/matrix interfacial bonding, high porosity and the formation of angular-shaped pores were resulted in the coating. Dry sliding wear tests results revealed that the wear resistance of the coating is directly related with the retained content of Al2O3in the coating. The coating containing irregular Al2O3particulates displayed superior wear performance with its wear rate one seventh of that of the pure A380 alloy coating. The coating containing both kinds of Al2O3particulates showed mixed characteristics of above two kinds of Al2O3composite coatings.