Microstructure evolution of laser remelted Al2O3-13Â wt.%TiO2 coatings

Laser remelting of plasma sprayed Al2O3-TiO2 coatings has been extensively investigated. However, little work on the microstructural evolution of laser-remelted Al2O3-TiO2 coatings has been reported. This study presents a detailed microstructural investigation of laser-remelted Al2O3-TiO2 coatings. Nanostructured feedstock has been reconstituted from nano-sized starting powders. A compound process of plasma spraying and laser remelting has been applied to fabricate the Al2O3-TiO2 coatings on titanium alloy. The evolution of microstructures of laser-remelted Al2O3-TiO2 coatings was investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy-dispersive spectrometer (EDS) and transmission electron microscope (TEM). Microstructural observations revealed microstructure correlation throughout the compound process. It was found the α-Al2O3 in feedstock was transformed to γ-Al2O3 after plasma spraying, which was completely transformed into stable α-Al2O3 phase after laser remelting. Bi-modal microstructure features are found for the laser-remelted coatings. For nanostructured coating, the net structure of its remelted coating resembles that of its feedstock and as-sprayed coating. For conventional coating, the strip-like structure of its remelted coating also resembles that of its feedstock and as-sprayed coating.