Relationship between microstructure and bonding strength of yttria-stabilized zirconia thermal barrier coatings

Abstract Yttria-stabilized zirconia coatings were prepared by atmospheric plasma spraying, and the bonding strength of the coatings was determined by tensile testing. The microstructure of the coating, including grains and pores, was characterized using scanning electron microscopy and electron backscatter diffraction. The results show that the higher the proportion of columnar grains, the higher the bonding strength. The large misorientation at the small grains leads to large stress, which is easy to fracture in the tensile process, so the existence of small grains leads to poor bonding strength. By using image processing, pores were classified as holes, cracks, and microcracks, and their proportions were calculated. It was found that both holes and transverse and vertical cracks in pores linearly affected the bonding strength; the influence of holes was the greatest, and the influence of microcracks was the smallest. In conclusion, the smaller the porosity, the greater the bonding strength of the coating.