Cladding inner surface of steel tubes with Al foils by ball attrition and heat treatment

A method used to clad the inner surface of steel tubes with Al foils has been developed: Al foils were welded onto the inner surface of steel tubes by ball attrition in planetary rotation, followed by annealing at 660 °C for 20 min. SEM, EDS and XRD methods were used to analyze the microstructure, the composition and the phases of the cladding layer. Studies on the interface microstructure indicated that the bonding strength between Al foil and substrate is highly related to the rotation speed, diameter of alloy balls and treatment time. A high extent of plastic deformation increases the interfacial bonding strength. But severe plastic deformation may break Al foils and separate the foils from the inner surface. Subsequent annealing leads to the formation of multilayers of intermetallic compound and alloy phases through diffusion of Al, Fe, and other elements. This technique provides a simple but quite efficient way to improve the properties of inner surface of steel tubes.