Microstructural features and properties of plasma sprayed YPSZ／NiCrAIY thermal barrier coating （TBC）

The plasma sprayed thermal barrier coating (TBC) consists of NiCrAlY bond coating and yttria partially stabilized zirconia (YPSZ) top coating. NiCrAlY coating mainly contains Ni solid solution with face centered cubic lattice, Al2 O3 oxides and pores. The most obvious feature of YPSZ coating with tetragonal zirconia is a lot of vertical microcracks in this coating. The thermal insulation capability of the TBC increased with an increase in YPSZ coating thickness, the temperature drop across the TBC increasing from 60℃ to 92℃ with increasing YPSZ coating thickness from 100 μm to 500 μm. The thermalshock resistance of the TBC decreased with increasing YPSZ coating thickness and cracks initiated mainly in original vertical microcrack tips of the YPSZ coating and propagated not only along YPSZ coating / NiCrAlY coating interface but also through NiCrAlY coating. The oxidation process of the TBC at 1 200℃ can be divided into two stages: traasieat oxidation stage with rapid oxidation rate and steady oxidation stage with slow oxidation. Their transition time was about 10 hours. The weight gain for 100 hours was 3. 222 mg/mm^2. It is favorable to increase YPSZ coating toughness and to decrease the pores and oxides of the TBC system for improving thermal shock resistance and oxidation resistance of the TBC.