Tribological property and thermal shock resistance of NiCoCrAlY coated YSZ composite coatings prepared by different laser additive manufacturing scanning speeds

The operating efficiency of aeroengine is significantly affected by the airtightness of its gas path. In this work, the NiCoCrAlY-coated YSZ powder was used and the NiCoCrAlY/Yttria-stabilized zirconia (YSZ) composite coatings were deposited on IN718 substrate with different laser scanning speeds by laser melting deposition to fabricate the seal coating to improve the airtightness. The microstructure, tribological property and thermal shock performance of composite coatings were studied. Due to the extremely high laser energy density, the composite feeding materials are melted thoroughly as well as the IN718 substrate, forming a metallurgical bonding between the composite coating and the substrate. Compared with the pure NiCoCrAlY coating, the reinforced phases γ-NiAl, γ-Ni, ZrO2 and Al2O3 were generated in the composite coating because of the decomposition of YSZ ceramic particles. Due to the uniform nucleation and refined grains, the hardness improves in composite coating hence the wear resistance compared with the pure NiCoCrAlY coating. With increasing laser scanning speeds, the length and width of the microcracks in the composite coating increased correspondingly, thus degrade the thermal shock resistance. The sample prepared by the laser scanning speed of 8 mm/s shows the best wear and thermal shock resistance in this work since its less microcracks while moderate grain size.