Plasma Spray Preparation Of Nanostructured Zirconia Thermal Barrier Coatings

Thermal barrier coatings(TBCs) are widely used in aerospace, power generation,chemical industry,metallurgy and many other fields. Traditional micron TBC is brittle and easy to crack.Brittleness of nanostructured TBC can be reduced and its toughness can be improved. In this paper,ZrO₂-8 wt.%Y₂O₃ agglomerated powder with calcination at 1250℃for 2 hours was used as starting material,NiCrAlY alloy was used as an intermediate layer,and nanostructured TBC was deposited on nickel and stainless steel substrates by atmospheric plasma spraying method.TBC samples were heat-treated at 1100-1250℃for 2 h.X-ray diffraction,scanning electron microscopy,transmission electron microscopy and other analytical instruments were used for the analysis of powder and coating samples.Surface morphology,microstructure,grain size and phase composition of the TBC samples with and without the high temperature heat treatment were investigated.Experiments on the thermal shock and spallation behaviors of the nanostrcutured TBC were conducted.Experimental results show that the nanostructured TBC not only has fully melted,well stacked,and smooth region,but also has no melting or near melting,not well stacked,and rough region.New nano-grains formed in smooth region.Non-melting nano-particle agglomerates still remained original structure.Starting agglomerated powder is composed of monoclinic phase,tetragonal phase and cubic phase.Its main phase is cubic phase and next is tetragonal phase.The nanostructured TBC is composed of major tetragonal phase and minor cubic phase.After high temperature heat treatment,the surface morphology of the nanostructured zirconia TBC did not change obviously, and the phenomenon of nano-grains growth happened.The heat-treated TBC is still composed of cubic phase and tetragonal phase,but with the increase of heat treatment temperature and time the content of cubic phase increases and the content of tetragonal phase decreases.Thermal shock property of the nanostructured TBC is better than that of traditional micron TBC.