Single crystal superalloy is the most important blade material of advanced gas turbine engine. China has made remarkable achievements in the research and development of single crystal alloys and their processes, but it is still far behind the international advanced level. Due to the complexity and instability of the production process, as well as the long development cycle, high cost and low yield, the development process of single crystal blade in China is slow, which restricts its practical application in the advanced aeroengine. In view of this technical bottleneck, digital, network and intelligent technology are introduced into the manufacturing process of superalloy turbine blades. The computer simulation technology is used to effectively simulate the solidification microstructure evolution process of directionally solidified blades, analyze the solute diffusion, melt flow and temperature distribution at the front of solid-liquid interface, and predict the generation of crystal defects, Finally, the purpose of optimizing the production process, shortening the trial production cycle, reducing the trial production cost and improving the quality and yield of single crystal blade is realized.
The purpose of studying the application of digitalization, network and intelligence in the aviation industry is to promote the casting technology to take a high-end road. At present, China’s casting production has been ranked the first in the world, but it is large but not strong, and its weight is not heavy. Many high-end casting products still rely on foreign imports, and they have not fully mastered the forming and manufacturing technology of high-end castings such as hot end parts of aeroengine, so the qualification rate is low. In addition to the raw materials, the lack of effective prediction and control means is also one of the important reasons. Many years of research work has shown that by integrating computational fluid dynamics, computational heat transfer, computational materials and structural performance models, it can comprehensively predict the evolution laws of various physical quantities in the casting forming process, predict the changes of material microstructure and various defects in the casting forming process, and reflect the effect of process parameters holographically, It provides a powerful tool for optimizing theand improving the product quality. The feasibility of this technology development has been fully verified in the research field, which is expected to fundamentally change the current situation of directional solidification production technology level of Superalloy blades, and promote the progress of manufacturing technology level of aviation industry in China.
Although digitalization, networking and intelligence have great potential to reduce costs and accelerate the development of new products in the aviation industry, the following problems need to be solved in order to make it widely used in the aviation industry:
(1) The integration of multi-scale, multi physical, forming and manufacturing process simulation.
The multi-scale coupling simulation of directionally solidified superalloy blades can be understood from two aspects: time scale and space scale. In terms of time scale, on the one hand, it is the simulation of the coupling relationship between the directional solidification process, microstructure, mechanics and service performance; on the other hand, it is the coupling between different forming processes, that is, the whole manufacturing process. For the manufacturing of blades, there are complex manufacturing processes such as casting (directional solidification), heat treatment, laser drilling and ceramic coating. In terms of spatial scale, it is mainly the coupling simulation on the micro scale mesoscopic scale macro scale. Different scales correspond to different simulation means, methods and tools. The coupling between simulation means / tools, data transfer and information transfer of boundary conditions are the main problems.
Multi physical field coupling refers to the interaction of multi physical fields involved in the directional solidification process of superalloy turbine blades. These physical fields mainly include: flow field, temperature field, solute field, microstructure field, stress / strain field, etc. Some of these physical fields are one-to-one correspondence, some are the mutual influence between the two, some are the coupling relationship of three or more, how to establish the coupling relationship model and find a reasonable decoupling method is the focus of research.
(2) Experimental technology and database are the important guarantee of digitalization, network and intelligence.
Material basic data, microstructure and performance models are both based on theory and phenomenon, but no matter which model is not perfect, more experimental data are needed to modify, and more experimental data are also needed to be covered by the model. The research shows that 50% – 80% of the development cost of digital, networked and intelligent tools is related to experimental research. The experimental method is not only the premise of establishing the theoretical model, but also can make up for the theoretical deficiencies. The importance of experiments is also to ensure the accuracy of simulation software.
(1) Target to be achieved by 2020:
In order to realize the numerical simulation and defect prediction of crystal growth and dendrite growth, and to optimize the directional solidification process of superalloy blade, a perfect database of thermophysical parameters of single crystal superalloy material was established.
(2) Target to be achieved by 2025:
A perfect constitutive model of single crystal superalloy is established to simulate the thermal stress and strain accurately, to realize the recrystallization prediction of single crystal superalloy casting, and to realize the modeling, simulation and process of heat treatment process of superalloy blade.
(3) Target to be achieved by 2030:
In order to achieve the multi-scale, whole process modeling and numerical simulation of the preparation process microstructure service performance of single crystal superalloy blades, and to achieve the mechanical properties and service life prediction of blades.