Thermal Shock Resistance Analysis And Optimization Of Thermal Barrier Coatings With Network Structure

Thermal barrier coating(TBC)is a ceramic layer deposited on the turbine blades of the engine,with good corrosion resistance and wear resistance,and can resists high temperature.The application of TBC on engine parts not only improves the working temperature of engine,but also reduces fuel consumption,improves efficiency and prolongs the service life of parts.However,due to the large difference in thermal properties between TBC and superalloy substrate,large thermal stress will be produced under service condition,which will lead to the spalling of the coating.In order to solve this problem,to improve the bonding strength between TBC and substrate,to further understand the failure mechanism of thermal barrier coatings,and to pave the way for the future design of thermal barrier coatings interlayer,in this paper,the traditional TBCs and TBCs with network structure interlayer of different shapes and sizes will be prepared.The bonding layer and network structure interlayer will be prepared on the superalloy substrate by laser rapid prototyping technology,and the ceramic coatings will be prepared by plasma spraying.The thermal shock resistance of the traditional TBC and the TBC with network structure interlayer were compared by thermal shock experiment.In this paper,a two-dimensional numerical model based on the theory of thermo elastic plastic mechanics is also established for finite element numerical simulation,to analyze the influence of network structure interlayer on the stress distribution of TBCs,the influence of network structure with different sizes and shapes on the stress distribution of TBCs and the influence of network structure on the expansion of vertical cracks and transverse cracks in TBCs.The conclusions were summarized as follows:1.The network structure changes the stress distribution in the thermal barrier coating.It reduces the tensile stress concentration in the vertical direction and the compressive stress in the horizontal direction at the edge of the thermal barrier coating,which improves the thermal shock resistance of the coating.2.Increasing the width and distance of the pad edge will increase the stress concentration in the vertical direction at the edge of the thermal barrier coating,which is not benefical to improving the thermal shock performance.But the increase of edge width and edge spacing will result in a reduction of the stress concentration near the pad.And quadrilateral network structure interlayer has the best effect on improving thermal shock resistance of thermal barrier coating.3.The pad has a guiding effect on the propagation of the vertical crack.The vertical crack will crack along the pad,and the network structure divides the ceramic layer into several small pieces,which increases the strain tolerance of the thermal barrier coating,and reduces the influence of the peeling ceramic layer on the adjacent ceramic layer.4.The addition of the network structure,can reduces the tensile stress in the vertical direction of the crack tip during the heating process and compressive stress in the direction of horizontal direction during the cooling process,which restrains the transverse crack caused by the vertical crack;5.The network structure reduces the compressive stress of ceramic layer in the horizontal direction during the heating process,and reduces the tensile stress in ceramic layer and bonding layer in vertical direction during the heating process,which restrains the expansion of transverse crack.