High temperature oxidation and thermal shock properties of La₂Zr₂O₇ thermal barrier coatings deposited on nickel-based superalloy by laser-cladding

In order to reduce the difficulty and cost of manufacturing and improve the high temperature oxidation and thermal shock properties of nickel-based superalloy, a thin La₂Zr₂O₇ thermal barrier coating without bond coat was successfully prepared by laser-cladding using La₂Zr₂O₇ powders on a nickel-based superalloy substrate. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods were used to characterize the microstructure of the coating. The high temperature oxidation and thermal shock properties of the coating were evaluated by the air isothermal oxidation method at 1100 °C for 110 h and thermal cycling method at 25~1100 °C, respectively. The results show that the coating is mainly composed of La₂Zr₂O₇ phase. The oxidation weight gain rate of the coating is about two-thirds of that of the substrate, and the first crack thermal shock lifetime of the coating is about 1.67 times of that of the substrate. The oxidation products of the coating are mainly Fe₂O₃, Cr₂O₃, NiCr₂O₄, Nb₂O₅ and La₂Zr₂O₇. The existence of La₂Zr₂O₇ phase in the coating is the main reason for the improvement of its oxidation resistance at 1100 °C and its thermal shock resistance at 25~1100 °C.