Integral blisk manufacturing technology

At present, the foreign blisk manufacturing technologies mainly include: welding technology, milling processing technology, precision forging manufacturing technology, electrolytic processing technology, etc. The technological process adopted is: precision forging + numerical control processing; precision welding + numerical control processing; high temperature alloy precision casting Blank + hot isostatic pressing. The main application of its manufacturing process technology is shown in Table 1. The United States, Britain, Russia and other developed countries are in a leading position in the field of integral blisk manufacturing, and they have advanced milling equipment and welding process equipment.

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In recent years, domestic research on the manufacturing technology of aero-engine blisks has reached a certain level, and the complete manufacturing of blisks has been realized. Through the analysis of the blisk structure and manufacturing process requirements, the domestic use of composite manufacturing processes is mainly divided into: Forming blank manufacturing, precision forming processing, surface polishing, surface treatment and other processes, each process stage has a variety of process technologies, and many process technologies are combined to form a variety of different overall blisk manufacturing processes. At the same time, some of them The domestic is still in the research and development stage, and its process flow and key technologies are shown in Figure 2.

Near-form blanking technology

The precision blanking technology of the integral blisk is developing in the direction of near-forming. The near-forming technology has become an important technology in the field of material processing. It has the characteristics of low cost, flexible operation and short market entry period, and solves the key points in the manufacture of the integral blisk. Manufacturing technology to improve production efficiency and achieve the goal of saving materials and energy. The near-form blanking technology in the manufacture of blisks mainly includes: precision forging technology, precision casting technology, electron beam welding technology, linear friction welding technology, etc.

01

Precision forging technology

At present, the integrated blisk mostly uses the precision forging process as a blanking method. This technology can not only save precious metal materials, reduce the machining amount of difficult-to-process materials, but also improve the fatigue strength and service life of the overall blisk. In modern precision forging technology, during the near forming process of the blisk, the blisk forgings are precisely designed. The blades and the disc are left with a small margin. It is necessary to ensure sufficient deformation and shape of the blades. The application of isothermal forging technology and superplastic isothermal die forging technology provides a guarantee for the blanking process of superalloy and titanium alloy compressor discs, and obtains excellent structure and mechanical properties.

The United States GE company applied isothermal forging technology to manufacture the compressor blisk rotor with blades, which increased the material utilization rate by 4 times. The dimensional accuracy of precision forged parts can reach 0.1~0.25mm, and the surface roughness can reach 0.4~1.6μm. Domestic Baoshan Iron and Steel Co., Ltd. has conducted in-depth research on the isothermal forging technology of titanium alloy integral blisk, and designed the simplification, refinement, mold, forming, etc. of the forging drawing, and carried out the forming test on the titanium alloy integral blisk, and the forging results showed , There is no folding and other defects in each part of the forging, and the shape is good.

02

Precision casting technology

Due to the new development of precision casting process and casting numerical simulation software technology, especially the in-depth study of the theory of directional solidification and hot isostatic pressing of metal materials, it is in improving the structure and performance of casting alloys, predicting casting size deformation, casting defects, and optimizing casting process. Playing an increasingly important role, not only greatly improves the structure and performance of the cast alloy, but also solves the problem of fatigue cracks on the blade surface along the grain boundary perpendicular to the main stress direction of the blade, improves the fatigue resistance of the blade and reduces the surface crack.

In the 1970s, the United States extensively carried out research on the casting process of integral blisks with directional blades and equiaxed fine-grained hubs, and successfully realized the dual performance integral blisk casting technology based on Mar2M247 and CM681 directional alloy materials, that is, the blades of the blisk are Oriented columnar crystal, roulette is equiaxed crystal.

The National Institute of Aeronautical Materials has conducted in-depth research on the precision casting technology of the integral blisk, analyzing the selection of dual-performance alloy materials, the formation method of the integral blisk structure, control measures, casting process parameters, and the effect of heat treatment on the mechanical properties of the blisk. , Designed a special device for the casting process to obtain a radial temperature gradient during the blade solidification process, and successfully cast a turbine blisk with a diameter of 120mm and 34 blades through different test schemes, as shown in Figure 3.

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Figure 3 The casting sample of the integral blisk

03

Electron beam welding technology

Electron beam welding is a method of using accelerated and focused electron beams to bombard weldments placed in vacuum or non-vacuum, and use the generated heat energy to perform welding. Electron beam welding is easy to realize deep penetration welding of metal materials. It has the advantages of narrow weld seam, large aspect ratio, small weld heat-affected zone, easy and precise control of welding process parameters, good repeatability and stability, and it has the advantages of automatic Technical advantages such as seam tracking, fast flow deflection, and multi-melt pool welding make it widely used in aerospace and other industries.

Due to the early development of electron beam welding and the relatively mature technology, it was first used in the manufacturing process of the blisk. According to relevant data, the EJ200 third-stage fan blisk was the first blisk formed by electron beam welding technology. The individual blades are welded into a blade ring by electron beam, and then the forged and electrolytically processed disc web and the blade ring are welded to form an integral blisk structure by electron beam welding technology.

In China, the electron beam welding process of the blisk is mainly applied to the blisk of titanium alloy material, and many research institutions have carried out a large number of research tests on the electron beam welding of the blisk. The Technical Center of AVIC Shenyang Liming Aero Engine Co., Ltd. conducted a lot of research on the deformation control method in the electron beam welding process of the TC4 blisk, and proposed a comprehensive application of welding process optimization, rigid fixation, vacuum heat treatment and electron beam local heating. Deformation control method, and through related experiments, effectively control the welding deformation, and realize the manufacture of the whole blisk structure of electron beam welding.

The electron beam welding blisk technology has been widely used in the domestic blisk manufacturing field due to its high stability, but its limitation is that it is only suitable for the welding process of titanium alloy blisks, and for the welding of high-temperature alloy blisks. There are major technical flaws, and more in-depth research is needed.