Microstructure and Mechanical Properties of Thermal Insulating Coating Prepared by Laser and Plasma

In this work, supersonic plasma spraying technology and the laser remelting process are used to prepare the zirconia thermal insulating coating. The macroscopic morphology of the zirconia coating is characterized by optical microscope, scanning microscope, energy spectrometer, X-ray diffractometer, and hardness tester. The results show that the coating phase prepared by laser and plasma composite consists of metastable tetragonal crystal phase and cubic crystal phase. The cross-section of the coating is bowl-shaped, and the upper edge is uneven. The composite preparation process eliminates the layered structure, pores, and micro-cracks in the original supersonic plasma spray coating, improves the density of the coating, and the connection between the coating and the substrate becomes metallurgical after remelting. The matrix structure obtained after remelting gradually changes from stripshaped crystal and needle-shaped crystal to fine needle-shaped crystal and perlite from top to bottom, and the structure of the heat-affected zone is equiaxed crystal. The average hardness of the remelted coating is about throe times of the hardness of the original plasma coating.