The three-layered structure of the NiCrFeAlBN-YSZ-NiCrAl coating can be seen in the cross-sectional SEM images of the coating in Fig.1(a). The bonding between the layers was good, and very few defects were observed at the interfaces. By using the image measurement method, the thickness of the intermediate layer was determined to be 379-395 um, which met the requirements for insulation and flame retardants. The porosity of the YSZ ceramic intermediate layer prepared by the optimized spraying process ranged from 10 to 15%, which is higher than that of traditional ceramic thermal barrier coatings, forming a transition area between the porous top layer and the bottom layer. Figure 1(b) displays the microstructure of the top layer of the NiCrFeAlBN coating. The bright phases are the metal matrix, while the dark areas are pores and homoge-neously distributed h-BN, which make the coating abradable.
The surface hardness and tensile bonding strength of the layered seal coatings are shown in Table 1. The mechanical properties of the layered seal coating met the basic application requirements of a surface hardness between 55and 70 HR15Y and a bonding strength higher than 4 MPa.Figure 2 shows the fracture surface of the tensile specimens. More than 70% of the fracture area was located in the top layer, and the rest was located at the interface between the top layer and the intermediate layer, likely because the top layer had the highest porosity and the weakest bonding under static tensile conditions. This also shows that the interfacial bonding between the layers is satisfactory.
Fig.1 SEM images of (a) the interface of the layered seal coating;(b) cross-sectional microstructure of the NiCrFeAlBN abradable seal coating
Table 1 Hardness and bonding strength of the layered seal coating
Fig.2 The fracture surface of the layered seal coatings after tensile tests
本文由桑尧热喷涂网收集整理。本站文章未经允许不得转载；如欲转载请注明出处，北京桑尧科技开发有限公司网址：http://www.sunspraying.com/
|
