Studying The Influence Of Laser Deposited Structured Bond Coating On The TBCs

As a new methods of high temperature protection thermal barrier coatings (TBCs) has been widely used in aerospace, petroleum chemical industry, machinery and other industries due to its excellent high temperature resistance, corrosion resistance, abrasion resistance and other properties. However, the low bonding strength of plasma sprayed TBCs will esily fall off the substrate under thermal shocking, which restricts the application of this technology. With the aim of improving the life of TBCs, it is proposed to use the laser direct deposition method to manufacture a mesh layer between the coatings and the substre. In this paper a mesh layer was first deposited by laser. After that the space between the mesh was filled by a layer of ceramic material with laser plasma spraying method. With the optical microscope (OM), X-ray diffraction (XRD), and scanning electron microscope (SEM) the forming precision of the manufactured mesh layer, the microstructure of TBCs and the propagation of crack. The bonding strength of coating and liner was measured by microhardness test and tensile test. The conclusions were summarized as followes:(1) The grid width of laser direct deposited mesh layer is 1 mm. Different structure such as triangle, square or hexagon can be fabricated. The grid fabricated by laser direct depositing can meet the requirement of the size and the accuracy of the actual application. The bonding strength of the mesh liner structure with substrate was 419 MPa, which is higher than that of the liner layer prepared by the thermal spraying obviously.(2) Preparing mesh structure liner on the surface of substrate could improve the bonding strength of the coating and the substrate. Compared the bond strength of the traditional structure with the thermal barrier coating with mesh structure, and results show the average bonding strength of the traditional thermal barrier coating and the thermal barrier coating with mesh liner was 8.18MPa and 10.7 MPa respectively, which mean that the bonding strength of thermal barrier coating increased by 30.8% after introducing mesh liner into thermal barrier coating system.(3) Compared thermal cycle life and results show thermal cycle life of the traditional thermal barrier coating and the thermal barrier coating with mesh liner was 5 and 8 respectively. It can be concluded that by introducing mesh liner into thermal barrier coating system, the thermal cycle life of thermal barrier coating increased by 60%.(4) The tensile and thermal shock test results indicate that the quadrilateral mesh liner structure on substrate which prepared by laser direct deposition can most significantly improve the performance of thermal barrier coating.