Laser remelting of plasma sprayed nanostructured Al_2O_3-TiO_2 coatings at different laser power

摘要

Plasma sprayed nanostructured Al_2O_3-13wt.% TiO_2 coatings were fabricated on a Ti-6Al-4V alloy using as-prepared feedstock. The as-sprayed coatings were remelted by a CO_2 laser. The coatings before and after laser remelting were characterized by using X-ray diffractometer (XRD), scanning electron microscope (SEM), energy-dispersive spectrometer (EDS) and Vickers microhardness tester. The effects of laser power on microstructure and properties of the laser remelted Al_2O_3-13wt.% TiO_2 coatings (LRmC) were investigated. The metastable γ-Al_2O_3 phase in the as-sprayed coatings was transformed to stable α-Al_2O_3 during laser remelting. The LRmC possessed much denser and more homogenous structure as well as an excellent metallurgical bonding to the substrate. Microstructural correlation was found in the coatings before and after laser remelting. The microhardness of the LRmC was enhanced to 1200-1800 HV_(0.3), which was much higher than that of the as-sprayed coatings and 3-5 times that of the substrate. The microhardness values were increased with increasing laser power.