Microstructure and properties of NiAl/NiCoCrALY/8YSZ composite coatings

The work aims to improve the corrosion resistance of metal/ceramic thermal insulation coatings in marine environment. NiAl composite coating and NiCoCrAlY bonding layer were prepared by cold spraying and formed to a multi-layer structure corrosion resistant and heat insulating coating system suitable for marine environment with 8YSZ ceramic coating prepared by plasma spraying. The surface and cross-section microstructure of bonding layer and ceramic layer were observed by field emission scanning electron microscopy (FE-SEM), and the elements distribution was analyzed by energy dispersive spectral (EDS). The phase compositions of coatings were characterized by X-ray diffraction (XRD). Bonding strength test was carried out by tensile test with universal material testing machine. Thermal cycle test and high temperature flame erosion test were used to investigate the high temperature resistance of the coating. Microscopic analysis showed that the morphology of NiAl composite coating and NiCoCrAlY bonding layer was compact, there was few obvious oxidation observed in the coating and the degree of particle deformation was different. Bonding strength between bonding layer and matrix was about 18.4 MPa. The interface of bonding layer and 8YSZ ceramic layer was closely bonded. The components of the ceramic layer were stable. No cracking, peeling or shedding occurred on the coating surface after 12 thermal shock tests and 1000 cycles of high temperature flame erosion. The composite coating prepared by cold spray and plasma spray has excellent thermal resistance and corrosion resistance. The metal coating prepared by cold spray has compact structure, low porosity and good bonding with ceramic layer, which can effectively improve the corrosion resistance of the coating system in corrosive environment. NiAl composite coating can alleviate the thermal matching problem between NiCoCrAlY layer and aluminum alloy substrate, thus enhancing bonding performance of the coating. © 2019, Chongqing Wujiu Periodicals Press. All rights reserved.