Coaxial laser cladding of Al2O3-13%TiO2 powders on Ti-6Al-4 V alloy

Spray-dried sintered Al2O3-13wt. %TiO2 powders were directly coated on Ti-6Al-4 V alloy by coaxial laser cladding. The microstructure, elements distribution and phase analysis of the cladding sample were studied by optical microscopy, EPMA, SEM and XRD methods. The results indicated that the coatings with fine metallurgical bonding to the substrate comprised major stable α-Al2O3 and demonstrated three different regions of solidification microstructures. One region, at the bottom of the molten pool, contained mainly Ti enrichment columnar grains and randomly scattered ceramic particles, named Transition Zone. The second region, within the 0.1 mm scope above the transition zone, contained mainly fine equiaxed Al2O3 grains. The third region, at the upper zone of the molten pool, showed coarse equiaxed and cellular Al2O3 grains with obvious segregation of Ti and V elements. The mechanisms of microstructure formation, elements migration and segregation in the experiment were discussed.

► Dense Al2O3-13%TiO2 coating with fine bonding to Ti-6Al-4 V alloy is obtained.
► A fine equiaxed grain zone is formed at 0.1 mm scope above the transition zone.
► Major α-Al2O3 and TiO2 phases are detected without γ-Al2O3 phase.
► Molten drop impact to fusion surface shows obvious effect in relation to the segregation.