Effect of laser remelting on erosion behavior of plasma-sprayed thermal barrier coatings

The ZrO₂-7% Y₂O₃ thermal barrier coatings fabricated by plasma spraying on TiAl alloy surface were remelted by laser.The microstructures of the plasma-sprayed and laser-remelted coatings were compared by using scanning electron microscopy(SEM).Meanwhile,the erosion experiments of the coatings were carried out and the erosion failure mechanisms were discussed.The results show that the as-sprayed ceramic coating has a typical lamellar stacking characteristic.However,the laser-remelted coating exhibits a compact remelted zone which is composed of column-like grains along the direction of the heat current.The laser-remelted coating has better erosion resistance than the plasma-sprayed coating.Both as-sprayed and laser-remelted coatings show a brittleness erosion mechanism.Owing to the limited bonding at the interfaces between lamellar,the spalling of ceramic particles from the lamellar interface may be mainly responsible for the erosion of the as-sprayed coating;in contrast,cracking occurs within region near the surface of the laser-remelted ceramic coating which makes erosion occur by removal of these small blocks.