Research On Thermal Insulation And High Temperature Oxidation Resistance Properties Of Rare Earth Doped Zirconia-Based Thermal Barrier Coatings

With the development of naval gas turbine,high temperature resist-ance limit of turbine blades has become the primary restrictive factor for the increase of output power and efficiency of gas turbines.The application of thermal barrier coatings can greatly reduce the surface temperature of superalloy components of blades and it play an important role in thermal protection of marine gas turbine blades.Good thermal insulation,phase stability,high-temperature oxidation resistance and salt spray corrosion resistance is necessary for thermal barr-ier coatings serving in marine environment.In order to improve the perfor-mance of thermal barrier coatings,rare earth oxide Sc₂O₃ is doped into the traditional YSZ coating materials to construct a Multi-Solid solution mate-rial system.The effects of temperature,doping concentration,nanopore size and number on the thermal conductivity and oxygen diffusion rate of YSZ and ScYSZ thermal barrier coatings were studied,and the effect of salt spray corrosion on the mechanism of thermal insulation deterioration in Porous coating was analyzed.Based on molecular dynamics simulation,thermal conductivity and oxygen ion diffusion rate of YSZ and ScYSZ dense material under different temperature,doping concentration and nanopore were obtained.The results show that temperature has little effect on thermal conductivity at high temperature,but the diffusion rate of oxygen ions increases sharply with the increase of temperature.At 1273 K,the diffusion rate of oxygen ions in ScYSZ is much lower than that in YSZ,so the oxidation resistance of ScYSZ is better.Sc₂O₃ doping can reduce the thermal conductivity and oxygen diffusion rate of YSZ coating,and the doping ratio of Sc₂O₃ and Y₂O₃ has little effect on conductivity of ScYSZ.When the doping ratio of Sc₂O₃ and Y₂O₃ is 1:1,oxygen diffusion rate of the ScYSZ coating achieve lowest.Nano-pore can reduce thermal conductivity and oxygen diffusion rate of coatings,and nano-pore with small pore size is more conducive to increase thermal insulation and high temperature oxidation resistance of thermal barrier coatings.The structure and phase composition changing of porous coatings during salt spray corrosion were analyzed.Two-dimensional structure models of porous coatings at different perieds of high temperature salt spray corrosion were constructed using QSGS four-parameter random construction method.The decline mechanism of thermal insulation performance of YSZ and ScYSZ porous thermal barrier coatings with 10%porosity was calculated by lattice Boltzmann method.The results show that the equivalent thermal conductivity of the porous coating of ScYSZ is 47.1%lower than that of YSZ before corrosion;the thermal insulation performance of the porous YSZ coating decreases rapidly during 100h corrosion,while the porous ScYSZ coating of maintain good thermal insulation performance in high temperature salt spray environment.