In order to meet the requirement of long-term service of thermal barrier coatings (TBCs) in high temperature environment, the morphology evolution of coating/substrate interface and the laws of element diffusion of TBCs in thermal shock environment were studied in this paper. The thermal shock tests of TBCs was carried out by the quartz lamp heating platform. The microstructure and element distribution of the coating/substrate interface after thermal shock were analyzed by SEM and EDS, and the diffusion coefficient of Al element at the coating/substrate interface was calculated by Boltzmann-Matano diffusion model. The results show that the BC layer was mainly composed of β and γ phases, and the diffusion zone has appeared at the coating/substrate interface. With the thermal shock tests, the rapid consumption of Al element caused the gradient shift of Al element concentration between BC layer and substrate, and Al element began to diffuse outward. Some refractory elements enriched in the topologically close-packed (TCP) phase could be solidly dissolved into the substrate again. Finally, the distribution of all elements gradually uniform in the interface region. The diffusion coefficient of Al element was positive before the thermal shock tests and negative after 600 cycles. The maximum diffusion coefficient appears at the coating/substrate interface. And the greater the distance from the terface, the lower the diffusion coefficient.

With the rise of 4D printing technology in recent years, Kagome truss structure with excellent mechanical properties is gradually applied to high heat transfer equipment as a new type of disturbance unit. For the array jet structure in the flame cylinder, a teardrop-shaped Kagome truss structure was placed in its jet space and the numerical simulation method was verified through experiments; the influence of the structural parameters on the heat transfer characteristics of the target surface was investigated by numerical simulation calculation method; The correlation equations of the Nussle number and the pressure loss of the target surface were fitted based on the calculated data, and the optimal structure was calculated under the range of the structural parameters. The results show that the fitted second-order response surface model is accurate with the prediction error being less than 1.70%. The effects of truss structural parameters d and α are more significant for average Nussle number Nu_ave, while d, α, β² and α*β are more significant for pressure loss coefficient C_p. When the optimal structural parameters are d = 1.000 mm, α = 45.001°, β = 46.623°, the errors between the optimized results and the simulated results for Nu_ave, C_p and comprehensive impact fact F were 1.24%, 0.18% and 1.20%, respectively. C_p is 0.93% less, Nu is 12.78% more, and F is 13.13% more in the optimized part compared to the test part.

Polycrystalline and amorphous mullite fibers are employed as reinforcing phases in preparation of silicabased ceramic cores, respectively, and the effects of mullite fiber types on property of ceramic cores are investigated. Amorphous fibers are not so obvious as polycrystalline fibers in promoting crystallization of cristobalite, reducing shrinkage, and increasing porosity. Compared to polycrystalline fibers, the amorphous fibers have disordering structure similar to silica glass, they are easy to form tight binding with the matrix, enhancing the strength and creep resistance of ceramic cores. Moreover, the metastable structure of amorphous fibers ensures the high chemical activity in alkaline solutions, and the ceramic core exhibits excellent leaching rate. The silica-based ceramic core with a mass fraction of 3% amorphous mullite fibers exhibits excellent comprehensive performance, with bending strength of 27.7 MPa at room temperature and 22.4 MPa at high temperature, high temperature creep deformation of 0.31 mm, and leaching rate of 1.26 g/min, which can well meet the casting requirements of hollow blades.

To realize the demand of processing the air film hole of aviation turbine blade without metamorphic layer, the EDM–drilling combined machining system was developed. According to the demand of the system mentioned above, to work and control in coordination with two axes, system architecture needed to be designed and optimized, which ensures that EDM and drilling operate independently of each other. Meanwhile, the system can realize automatic control of motor spindle speed and the stepless adjustment of feed rate. Based on the combined machining system, a processing technology of micro-hole composite without metamorphic layer was developed. During the processing, firstly, a micro-hole was processed by EDM. In order to removal the metamorphic layer on the hole wall completely, where the hole needed reaming with drilling tool. The basis of the technology mentioned above, a series of compound processing experiments of straight hole and 20° inclined hole were carried out. The tolerance range is (0.315±0.003) mm. The experimental results show that the EDM–drilling composite machining has the advantages of high machining efficiency, high hole shape accuracy and no metamorphic layer on the hole wall.

To meet the long-term use requirements of high performance aero-engine in high-temperature gas environment, SiC-based self-healing ceramic matrix composites (SHCMC) are developing towards the oxidation resistance in high-temperature water vapor environment. This paper firstly clarifies the structural design principles of SHCMC based on the application requirements of it. And the great challenges faced by SHCMC at present were also introduced in detailed. Based on those, some progresses in SHCMC from high temperature stability of self-healing glass phase were reviewed in this paper. The SHCMC with self-healing ability in wide temperature range under the condition of water vapor conforms to the future development trend.

In the high-speed cutting, the severe plastic deformation and extremely high cutting temperature tend to cause the microstructure defects of the machined surface, which become the potential risk of fatigue fracture in the process of workpiece service. In this work, the microstructure evolution and formation mechanism of the machined surface for high speed machining GH4169 superalloy were studied combined experiment and finite element simulation. The high speed orthogonal cutting experiments were carried out, and electron back scattering diffraction (EBSD) technique was used to observe the microstructure of the machined surface material. Then, the finite element analysis model of high speed orthogonal cutting of GH4169 superalloy was established based on the modified Johnson – Cook constitutive model. The temperature field and strain field of machined surface material were obtained. The results show that the temperature, strain, and microstructure of the machined surface materials present a significant gradient distribution, and the grains of the nearsurface materials are refined to nanometer level. The gradient distribution of the machined surface material microstructure is caused by the gradient distribution of the force-thermal loads generated in the cutting process.

Efficient numerical control (NC) machining is the development trend of aero-engine blade production. In this thesis, a fast process benchmark preparation technology is proposed to solve the problem that it is difficult to achieve efficient machining due to the lack of benchmarks in the current NC machining of casting blades. Firstly, the blade profile data is quickly obtained by on-machine measurement or special measuring tools. Secondly, the fitness function with penalty term is designed, and the improved particle swarm optimization (PSO) algorithm is used to register the blade profile data and the blade theoretical model. Then, the process benchmark is prepared on the blade tenon or auxiliary fixture based on the blade body profile to ensure the accuracy, rapidity and reliability of blade clamping in subsequent NC machining. Finally, it is verified by examples that this technology can quickly and accurately realize the preparation of casting blade benchmarks, which meets the high-efficiency production requirements of casting blades.

This study is aimed at investigating the measurement of contact stress and its distribution pattern across the attachment surface of an aero-engine casing flange. To begin with, a dynamic contact stress measurement system for casing flanges was established based on MXene flexible pressure sensors with an ultra-wide pressure monitoring range. The measurement system was sandwiched by two flanges, and up to 13 measurement points were distributed therein. The stress changes of the corresponding measurement points were obtained in real time according to the time-domain response of the sensor resistance change rate and the pressure calibration curve. The comparison of the test results with the simulation shows satisfactorily consistent trends, displaying stress errors lower than 7%. Subsequently, the influence of structural parameters and pre-tightening torque on contact stress were studied, and possible measures for improving the sealing performance were applied. The findings suggest that not only can the proposed analytical method and measurement system provide accurate dynamic measurements for contact stresses, but the studied influencing relationship can also serve as a reliable reference for upcoming sealing performance optimization design for flanges. Last but not least, owing to the universal applicability of the methods presented, this research method also offers an invaluable guidance for contact stress measurements and distribution analyses of various casing flanges.

The blade has the characteristics of complex structure and many free-form surfaces. In order to solve the problem of preregistration of blade dense measurement data and its CAD model, a six-point optimization localization algorithm was proposed for preregistration. Combining the six-point positioning principle and dock planner must, the original coordinate system is established on the tenon reference plane, and the positioning error analysis and registration is performed on the primary and secondary direction of six-point to reduce the error of each measuring point, so that the CAD model and the theoretical model achieve consistent state. Finally, the six degrees of freedom of point distribution is completed, and the final set of blade model dock planner must control points is obtained. It avoids the tedious calculation of ICP algorithm for processing a large number of point cloud data, and realizes the dense measuring point optimization preregistration of batch blades after six-point optimization positioning, and the positioning accuracy is about 0.02 mm. The registration results of six-point optimization positioning and typical six-point positioning are compared and analyzed. The preregistration accuracy of the six-point optimization positioning algorithm for blades is about 0.02 mm, which meets the accuracy requirements of blade model preregistration.

As important structural materials, niobium and stainless steel are widely used in the aerospace. However, brittle intermetallic compounds are easily formed, and high residual stress is distributed within the joint, which easily leads to cracking. In this paper, aiming at the current research status of niobium alloy and stainless steel welding, the main joining methods of niobium and stainless steel are reviewed: Explosive welding, brazing and fusion welding. Although explosive welding and brazing can suppress welding cracks, the complex welding process of explosive welding and the low joint strength of brazing are difficult to meet the application requirements of niobium/stainless steel composite structures. High residual stress distributed in the fusion welded joint, and many brittle Nb–Fe intermetallic compounds formed in the weld, resulting in poor mechanical properties of the joint. In view of the above problems, the fusion welding of niobium alloy and stainless steel is prospected: Conducting finite element simulation to guide welding process optimization, introducing a third component into the weld to improve the weldability of niobium and stainless steel, and exploring reasonable heat treatment processes to improve the mechanical properties of the joint.

In order to develop advanced flexible sealing technology for aviation, the brush sealing structure of GH4169+Haynes214 brush wire was developed by electron beam welding. The effects of different welding processes on the weld formability, microstructure characteristics, microhardness, and sealing performance of the welded joint were studied. The results indicated that the use of electron beam welding technology can achieve well-formed welded joints, without crack and pores. The microstructure of the weld joint was a dendritic crystal with short transverse dendrites and long main axes, mainly composed of γ, γ' and γ'' (Ni₃Nb), and eutectic structure is formed between short transverse dendrites (γ+ Laves). The carbides in the fusion line region were grown and agglomerated at grain boundaries under thermal cycling. The microhardness of welded joint was approximately symmetrically distributed, with an average hardness of approximately 435HV in the weld area, which was smaller than base metal (approximately 540HV). Because the weld area was mainly Haynes214, which contained high Ni and Al content. During the welding solidification, Haynes214 was mixed with GH4169 alloy elements, resulting in changes in microhardness caused by differences in the microstructure of the solidified welded metal. The leakage rates of the brush sealing structure were less than 20 g/s at room temperature (20 ℃) and high temperature (403 ℃). At room temperature (20 ℃), the leakage coefficient was stabilized around 0.006, which was less than the expected leakage coefficient of 0.007. When heated to 403 ℃, the leakage coefficient gradually increased with the increase of pressure, and finally was stabilized around 0.004, indicating that the brush seal structure has excellent sealing performance and can be promoted and applied in aerospace engines.