Spray parameters of ZSTK474 bond coat and the YSZ.ParameterBond coatYSZSet 1Set 2Power (kW)12.52130Current (A)250300500Voltage (V)507060Primary gas Ar (L/min)3028.928.9Secondary gas H2 (L/min)555Powder feed rate (g/min)101010Spray distance (mm)100100100CPS330471Full-size tableTable optionsView in workspaceDownload as CSV
2.3. Microstructure characterization
2.4. Thermal conductivity measurement
Fig. 2. The equipment designed to measure the thermal conductivity of the TBCs.Figure optionsDownload full-size imageDownload as PowerPoint slide
The heat flux density of the coating samples under steady temperature gradients can be expressed asequation(2)q1=t0−t1(δ1/λ1)+(δ2/λ2)
It also could be stated as:equation(3)q2=λ2(t0−t2)δ2
Simultaneously, the heat transfers between the hearth and the ambient air can be termed asequation(4)q1=h(t1−t3)q1=h(t1−t3)equation(5)q2=h(t2−t3)q2=h(t2−t3)
According to Eqs. (2), (3), (4) and (5), the thermal conductivity of the coatings can be calculated by:equation(6)λ1=δ1λ2(t0−t1)(t2−t3)δ2(t0−t3)(t0−t2)−δ2(t0−t1)(t2−t3)where t0 is antibody-mediated immunity the temperature in the box furnace; t1 is the rear surface temperature of the coated sample; t2 is the rear surface temperature of the bare substrate; t3 is the ambient temperature; δ1 is the thickness of the YSZ coating, 0.25 mm; δ2 is the thickness of the substrate with a measured value of 5.6 mm; λ2 is the thermal conductivity of the FeCrAl alloy supplied by the producer (20, 21.4 and 22 W m−1 K−1 at 300–500 °C); h is the heat convective coefficient in the air.