REDUCTION OF INTERCONNECTED POROSITY IN ZIRCONIA-BASED THERMAL BARRIER COATING

Chemical vapour deposition of zirconia was carried out on yttria-stabi lized zirconia based thermal barrier coating to close down the surface pores. Scanning electron micrographs of the surface and the cross-sec tion indicate that the surface cracks and pores could be closed and th at the deposited layer penetrates the plasma-sprayed yttria-stabilized zirconia layer. The interconnected porosity, determined by the measur ement of diffusion current density in 5% NaCl solution, was found to b e reduced to about 98% even by a 10 mu m thick overlayer.