Turbine blades play a crucial role in turbomachinery, guiding fluid flow and driving rotor rotation. They are indispensable key components in turbomachinery such as aero-engines. As the crown jewel of modern industry, aero-engines and their related blade manufacturing are even hailed as the "pearl on the crown". With the rapid development of China's aviation industry, domestic blade manufacturers have continuously enhanced their position in the international market, gradually entering the trillion-scale market threshold of aviation blade manufacturing. This marks significant progress in the high-end field of China's aviation manufacturing industry, injecting new vitality into the development of the country's aviation industry. By continuously improving technological levels and strengthening research and development innovation, China's blade manufacturing enterprises will be able to compete in the international market and make greater contributions to the development of the aviation industry. Turbine blades are key components of turbofan engines: 
Turbofan engines are widely used in fighter jets, transport aircraft, passenger planes, and drones, and are currently the most core aviation engines. Various types of blades (including fan blades, compressor blades, and turbine blades) are the core components of turbofan engines, accounting for more than 30% of the workload in engine manufacturing. Among them, fan/compressor blades are cold-end components, mostly made of titanium alloy materials, with the use of composite materials increasing continuously. Turbine blades are hot-end components, made of high-temperature alloys and other materials, and processed through precision casting. They are the most difficult and costly blades to manufacture in turbofan engines, accounting for more than 60% of the total value of turbofan engine blades. Aero-engines are very complex thermal devices, and they are the heart of the entire aerospace industry. Aero-engine structures are extremely complex, with modern engines consisting of tens of thousands of parts that need to operate reliably under harsh conditions such as high temperature, high pressure, high speed, and alternating loads for extended periods. Globally, only the United States, Britain, France, Russia, and China are likely to possess their own aircraft engines. A country's level of science and technology, industrial level, and overall strength are all marked by its engines. 
The fundamental principle of various gas turbine engines is to compress air and inject fuel into it to obtain high-temperature and high-pressure gas, and then convert the internal energy of the gas into mechanical energy. In this process, the turbine blades responsible for extracting the energy from the gas face the impact of high-temperature airflow, especially the first-stage turbine blades, which are in the harshest working environment. The turbine inlet temperature of advanced turbine engines exceeds 1600℃, which not only far exceeds the heat resistance limit of nickel-based superalloys but even surpasses the melting point of the alloy. Therefore, the most advanced materials, structures, and processes are used for manufacturing. 
Turbine blades are key components in turbofan engines, accounting for approximately 30% of the entire engine production in terms of workload. In turbofan engines, the use of many high-strength alloys and titanium alloys has greatly improved their overall performance. Among them, fan blades, compressor blades, and turbine blades, among other types of blades, serve in service environments and are made of high-strength metallic materials with increasingly complex structures and greater manufacturing difficulties, which have become a bottleneck restricting the development of aero-engines. The production of various specifications of blades accounts for more than 30% of the entire engine production. At present, there are three main methods to increase the turbine gas temperature: firstly, developing new high-temperature alloy materials to continuously enhance the temperature-bearing capacity of the blades; secondly, developing new thermal barrier coatings; and thirdly, improving the air cooling structure of turbine blades to enhance the cooling efficiency of the blades. In the manufacturing process of turbine blades, traditional forging, machining, and other methods cannot form complex internal cavity shapes of the blades, and only investment casting technology can be used for production. In investment casting, ceramic cores are formed to shape the internal cavity of hollow castings, and their performance and quality have a significant impact on the quality and pass rate of casting production. Ceramic cores are mold cores used to manufacture hollow casting transition pieces. Their function is to shape the internal cavity of hollow castings and ensure the dimensional accuracy of their wall thickness together with the shell mold or outer contour mold. Based on the characteristics and applications of ceramic cores, we temporarily define them as follows: under strictly controlled conditions such as composition, sintering, strength, and density, they can strictly control the geometric dimensions and dimensional accuracy of the casting cavity, and can produce special structural ceramic products with excellent internal chambers and a fine porcelain-like appearance. Ceramic cores bear high pressure from the wax liquid during the pressing of wax molds, and some products require the symmetrical pasting of a certain thickness of wax paper on the blade basin and blade back during the pressing process. While providing a certain flow path for the wax liquid, it prevents the ceramic core from being impacted by high-speed wax liquid and drifting. The wax mold should be free of undercutting, oil streaks, cold shuts, shrinkage pits, inclusions, bubbles, and cracks, without core misalignment, exposure, or breakage. Based on effective design, manual assembly is carried out to assemble the sprue cup, sprue runner, and blade wax molds to form a casting system. 
After assembly, check whether the wax mold and mold assembly identification are clear and accurate, and whether there are missing or duplicate numbers; whether the mold assembly sprues are used correctly, and whether the mold assembly method is correct; whether there are gaps, soldering defects, or mold damage at the welding points between parts and sprues; check whether the flanging of the sprue cup is smooth; then proceed with cleaning, and after cleaning, proceed with making the shell mold. After the shell mold cures to a certain strength, the mold shell that needs to be dewaxed is placed into a dedicated trolley, and the trolley is pushed into a dewaxing kettle. The ceramic core needs to undergo high-speed mechanical impact dewaxing, and during this process, it must be subjected to steaming with hot water and steam in the kettle. 
During the baking process of the shell mold, the following steps should be noted: Open the furnace door after the temperature drops to room temperature. Remove the trolley and manually take out the shell mold. The shell mold can only be opened when the furnace temperature drops below 200℃ to accelerate the cooling process. After the shell mold is removed from the furnace, remove the flanging of the sprue cup to ensure that it is facing up. Cover the entire shell mold with a dedicated disposable cleaning bag to prevent dust from entering. Prolonged heat exposure can affect the quality of the shell mold and core, so care should be taken to protect them. When inspecting the shell mold, the following steps should be taken: 
Inspect the shell mold group by group for defects such as cracks, missing parts, shell skin, and shell sand. Gently shake the shell mold from side to side to determine if there is any sound inside, indicating whether the core inside the shell mold is broken. Fill it with methylene blue alcohol solution to check for any leakage. Ceramic cores need to withstand high pressure, high-speed mechanical impact, hot water steam cooking, and long-term thermal effects during production. The core and shell mold jointly ensure the dimensional accuracy requirements of the casting cavity structure. During the production process, equipment such as foam ceramic filters and ceramic crucibles may be used. When casting high-temperature alloy blades in a vacuum smelting furnace, the following points should be noted: heat is mainly transferred through thermal conduction at the blade, mold, and blade-mold boundary. Between the mold and the furnace wall, as well as the water-cooled copper plate, heat is transferred through radiative heat transfer. As the alloy liquid solidifies from bottom to top, the mold gradually descends, while water cooling is applied at the bottom of the mold, forming a temperature gradient from cold at the bottom to hot at the top. This temperature gradient helps maintain a single direction of solidification from bottom to top, ensuring that the alloy grows into a single crystal structure. These steps help ensure that the high-temperature alloy blade can form an ideal single crystal structure during casting. Ceramic cores are mainly composed of silicon dioxide and aluminum oxide. After casting, they are treated with high-temperature and high-pressure alkali solution (NaOH/KOH) to dissolve and remove the cores. (This process is highly polluting and represents a technical bottleneck that needs to be overcome.) Excess sprues and risers are removed through machining to obtain the blade blank. 
The castings are heat-treated under vacuum and inert gas conditions together with the corresponding batches of test bars. They should be placed with the edge plate down and perpendicular to the ground to avoid mutual compression. 
The blade surface must be free of cracks, exposed cores, sand holes, scratches, cold shuts, under-casting, as well as linear, symmetrical, and penetrating defects. The blade surface must not exhibit oxidation. The transition radius (R) between the blade body and the platform, as well as the inlet and exhaust edges, must not have scratches or pits caused by mechanical effects. The roughness of the non-machined surface of the precision-cast blade should meet the requirements of the casting drawing. Using plasma arc as the heat source, the raw material powder for thermal barrier coatings is heated and sprayed onto the workpiece surface (another method is electron beam physical vapor deposition, which uses electron beam as the heat source). The thermal barrier coating consists of two layers: the outer layer is made of high-temperature resistant ceramic material, such as yttria-stabilized zirconia (YSZ); the inner layer is a metal bonding layer, which serves to buffer the difference in thermal expansion coefficients between the ceramic coating and the high-temperature alloy substrate, and to enhance the oxidation and corrosion resistance of the blade, typically made of MCrAlY (M=Fe, Co, Ni) alloy material. Through technological breakthroughs in blade dimensional requirements and metallurgical process difficulties, the following technologies have been developed: ceramic core technology: using ceramic cores to achieve complex shapes and precise dimensional requirements for the internal structure of the blade. Corundum shell technology: using corundum shells as casting molds to improve the surface quality and precision of the blade. Single crystal selection and directional solidification technology: through single crystal selection and directional solidification technology, the single crystal structure of the blade is achieved, enhancing its performance. Single crystal blade recrystallization control: controlling the recrystallization process improves the grain structure of the blade and enhances its mechanical properties. Ceramic core positioning technology: using ceramic core positioning technology to ensure the accuracy and stability of the blade structure. Through extensive testing and research work, the continuous improvement of these technologies has enabled the precision casting technology of hollow single crystal blades to meet design performance requirements, while also satisfying technical conditions in terms of metallurgical quality, microstructure morphology, chemical composition, and mechanical properties.