Experimental on preparation of thick ceramic coating by laser multi-layer cladding

The preparation of thick ceramic coating by squash presetting type laser multi-layer cladding with Al₂O₃-13%TiO₂ nanostructured agglomerated powders was studied.The crack of clad layer was controlled by preheating and slow cooling rate of sample with incubator,applying the ultrasonic vibration and closed-loop controlling temperature of molten pool during laser cladding process.The results show that the laser-clad thick ceramic coating has no obvious interface between the layers with dense,continuous structure,and almost no pores and large penetrating cracks.The coating is composed of fully melted zones(fine equiaxed grains) and partially melted zones(remained nanoparticles).In addition,the most cracks in the coating are present in the partially melted zone.Due to multiple heating by laser beam,the grain size of lower layer is bigger than that of upper layer,and the grain size of total coating is large because of the use of incubator.