With the complexity of the structure of aero-engine turbine blades, the blade wall thickness continues to decrease. It is found that when the blade wall thickness decreases to a certain extent, its mechanical properties will decline significantly. It is extremely important to study this phenomenon of a significant decline in mechanical properties caused by wall thickness. In this paper, the creep behavior of a second-generation Ni₃Al-based single crystal superalloy with different wall thicknesses and [001] orientation at 980 °C/220 MPa has been studied and compared with the creep life of Φ4 round bar. The experimental results show that the second orientation and the surface affected zone are not the main reasons for the reduction of the life of thin-walled samples under this experimental condition. By analyzing the fracture morphology and deformed microstructure of thin-walled samples with different thicknesses, it is found that the thickness debit effect of the single crystal alloy occurs since the effective stress area of the alloy changes due to internal defects and surface affected zone during the creep process. For thicker samples, the creep life of the alloy can be extended by making the samples undergo certain plastic deformation through better plastic deformation coordination ability, while for thinner samples, the plastic coordination ability is poor, and the ability to extend the creep life through plastic deformation is also weaker when the effective stress area of the alloy changes, which leads to the thinner samples being more prone to fracture.

Thermal barrier coatings (TBCs) exhibit excellent thermal insulation capabilities, proving crucial in enhancing the performance of turbine blades. Accurate measurement of TBC thickness is pivotal for the quality control and health monitoring of turbine blades. However, the absence of suitable non-destructive testing (NDT) methods poses a challenge in ensuring precise quality control and health assessment of TBCs. This study investigates the efficacy of terahertz time-domain spectroscopy (THz-TDS) in measuring TBCs thickness, specifically focusing on the microstructure characteristics of the top coat (TC), including grain morphology, internal porosity, surface roughness, and agglomerates. The findings emphasize the significance of grain morphology in determining thickness measurement due to the varied terahertz wave propagation modes. Moreover, the study involved polishing EB-PVD and APS samples to mitigate surface roughness. This process revealed a discernible linear correlation between reduced surface roughness and decreased measurement errors. The slopes of the error reduction curves ranged from 0.59 to 1.7 for EB-PVD and 2.17 to 5.79 for APS samples. Furthermore, the research observed THz light scattering within internal pores, resulting in diminished outgoing energies and subsequent increments in measurement errors.

Synchronous measurement of full-field temperature and deformation at high temperature especially more than 1273 K is of much significance especially for part applications of turbine structures and materials. Non-contact optical methods attract more and more attention, however, current methods all face different challenges, such as strong light reflection on the surface of the specimen, disturbing radiation from environment, complex equipment setup, limited measured temperature not higher than 900 °C and so on. In this work, we develop an innovative technique to overcome some current problems. The measurement system employing an ultraviolet (UV) imaging system is composed of a scientific complementary metal oxide semiconductor (sCMOS) camera, a lens and a UV bandpass filter. The UV bandpass filter was used for thermal radiation elimination to acquire high quality images at elevated temperatures for deformation field calculation suitable for digital image correlation (DIC) method. The UV sensitive sCMOS camera without using active illumination was employed to collect enough UV radiation energy and eliminate the interference of the external ambient light, which is applicable for high accuracy temperature field measurement. Our system can realize the synchronous capture of image and temperature acquisition with passive UV imaging system at temperature not lower than 1473 K. The feasibility of the method was verified through heating molybdenum (Mo) and Ni-based superalloy IC21 materials. The temperature fields of Mo measured by the established imaging system up to 1835 K with error less than 0.25% showed the effectiveness for temperature measurement. The estimated deformation and temperature field of Ni-based superalloy IC21 up to 1473 K with measured temperature error less than 0.5% demonstrated well the great potential of the UV imaging system in simultaneous measurement of temperature and deformation fields at elevated temperatures.

Slowing down the coarsening of the γ′ phase and suppressing the precipitation of the topologically close-packed (TCP) phase is crucial for optimizing the creep properties of Ni-based single crystal superalloys, which are affected by the solution treatment history. In the present study, the effect of cooling rate on the morphology, size and lattice misfit of γ′ reprecipitates after solution treatment, as well as the microstructural evolution (e.g., the coarsening of γ′ reprecipitate and precipitation of the TCP phase) and creep properties of samples under different cooling rates at 1100 °C were investigated. The findings suggested that as the cooling rate increasing, the size of γ′ reprecipitates decreased, while the morphology transformed from polygonal to cubic. Additionally, faster cooling rate, on the one hand, the lower the degree of lattice misfit of γ/γ′ phases, which is beneficial to slow down the coarsening of the γ′ phase; on the other hand, the supersaturation of the γ-phase was reduced, i.e., the Mo and Re contents in the γ matrix were lower compared to the slow-cooling sample, which led to a lower TCP phase area fraction during thermal exposure at 1100 °C. It is crucial that the creep life of the alloy significantly improved by increasing the cooling rate after solution treatment; this is facilitated by the formation of rafts from finer cubic γ′ phase and reduction in the TCP phase as a source of microcracks. In conclusion, the findings of this study provide new insights into suppressing the precipitation of the TCP phase and optimizing alloy heat treatment processes to improve creep properties.