Research On Microstructure And Performance Of NiCoCrAlY Coated YSZ Gradient Coating Prepared By Laser Cladding Technology

With the rapid development of the aerospace industry,the thrust-to-weight ratio of aeroengine is getting higher and higher,and the temperature of its combustion chamber is getting higher and higher.The service temperature of combustion chamber of the latest generation aero-engine has exceeded the limit temperature of nickel-based single crystal alloy currently,while coating or depositing thermal barrier coating on the surface of hot-end parts can effectively increase its service temperature.The technology level,material selection and composite structure can largely determine the microstructure and thermodynamic properties of thermal barrier coating,and then affect its service life.Therefore,it is of great practical significance to study the process,microstructure and properties of thermal barrier coatings prepared by laser cladding technonlogy.The main research contents of this article are as follows:Firstly,1 mm thickness NiCoCrAlY alloy powder was preset on the surface of IN718 alloy,and the laser cladding technology was carried out to prepare the NiCoCrAlY bonding coating.The dynamic relationship between laser process parameters,coating microstructure and properties was establish according to analyzing the microstructure and testing its microhardness and friction and wear properties of the coating.So the better laser scanning speed was selected,which was ready for the subsequent preparation of NiCoCrAlY coated YSZ composite coating and NiCoCrAlY coated YSZ gradient coating on the surface of bonding coating.Secondly,the NiCoCrAl Y coated YSZ composite coating was prepared by laser cladding technology with different laser scanning speeds on the surface of the bonding coating.The microstructure of the composite coating was analyzed,and its microhardness and friction and wear properties were tested.At last,the thermal shock resistance of the composite coating at different scanning speeds was explored,and the better scanning speed of cladding NiCoCrAlY coated YSZ composite coating was optimized.Finally,according to the optimal parameters,the gradient coating was cladding layer by layer on the surface of the bonding coating.The microstructure of the gradient coating was analyzed,and the thermal shock resistance and high temperature oxidation resistance of the gradient coating were tested.Meanwhile the crack generation and evolution mechanism,high temperature oxidation mechanism of the gradient coating were analyzed and studied,so which provided a certain experimental and theoretical basis for the preparation of the gradient coating by the laser cladding method.