Al2O3 thin coating of AA 6082 T6 components using a fast regime fluidized bed

Fluidized bed processing is a relatively novel method for coating metal substrates. A detailed study was carried out into surface property and in micro-structure changes induced by fluidized bed processing. In particular, fluidized bed processing of AA 6082 T6 aluminum alloy components using alumina Al2O3 powder was investigated. Firstly, the build up of Al2O3 films was studied and characterized in terms of coating thickness and adhesion. It was found that trends of deposited Al2O3 were consistent with fluidized bed processing time. Secondly, the effect of fluidized bed treatment on surface properties of processed components was examined. Surface morphology was significantly affected and its evolution according to processing time was accounted for. Both compressive residual stresses and increased dislocation density were induced by treatment of external layers of samples, and significant hardening was also detected. Lastly, the ability of fluidized bed processing was tested on 'ad hoc' fatigue samples. Rupture of fluidized bed treated samples as well as untreated samples was also discussed. At any rate, the fatigue behavior of processed components significantly improved. This quite new and unprecedented result is ascribed to the compressive residual stresses and work hardening induced by FB treatment in the outermost surface layers of the aluminum alloy.