The purpose of this paper is to study the thermal shock resistance and failure mechanism of La₂Ce₂O₇/8YSZ double-ceramic-layer thermal barrier coatings (LC/8YSZ DCL TBCs) under extreme temperature gradients. At high surface temperatures, thermal shock and infrared temperature measuring modules were used to determine the thermal cycling life and insulation temperature of LC/8YSZ DCL TBCs under extreme temperature gradients by an oxygen–acetylene gas flame testing machine. A viscoelastic model was used to obtain the stress law of solid phase sintering of a coating system using the finite element method. Results and Conclusion: (1) Thermal cycling life was affected by the surface temperature of LC/8YSZ DCL TBCs and decreased sharply with the increase of surface temperature. (2) The LC ceramic surface of the failure coating was sintered, and the higher the temperature, the faster the sintering process. (3) Accelerated life test results showed that high temperature thermal cycling life is not only related to thermal fatigue of ceramic layer, but is also related to the sintering degree of the coating. (4) Although the high temperature thermal stress had great influence on the coating, great sintering stress was produced with sintering of the LC ceramic layer, which is the main cause of LC/8YSZ DCL TBC failure. The above results indicate that for new TBC ceramic materials, especially those for engines above class F, their sinterability should be fully considered. Sintering affects the thermal shock properties at high temperature. Our research results can provide reference for material selection and high temperature performance research.

The preparation technology of graphene-based coatings on cobalt-based cemented carbides and the friction properties of graphene-based coatings were researched. Based on cooling rate, growth temperature, and methane flow rate, Raman spectroscopy was used to evaluate the influence of chemical vapor deposition (CVD) on graphene-based coatings. The results show that at the growth temperature of 1000 °C, the cooling rate of 15 °C/min and methane flow rate of 10 sccm are more favorable for the growth of pure graphene coating with fewer layers on a cemented carbide surface. As methane flow boosts, the number of graphene layers increases and amorphous carbon is generated. The resulting tribological properties demonstrate that the friction coefficient of graphene-based coatings decreases as the friction load increases. The above results indicate that the graphene-based coating on a cemented carbide surface can be prepared by regulating its composition and defects through technological parameters, and it is viable to use graphene-based coating as anti-wear coating for cutting tools. The results provide a reference for the preparation and properties of cemented carbide surface graphene.