Research on nickel-based casting high-temperature alloy and heat treatment process
With the development of science and technology, aerospace, automotive and other industries, industrial production requirements continue to improve, gas turbines, turbine blades magazine and other areas of high temperature parts, in order to adapt to the overall requirements of industrial production, the performance of the raw material requirements have also increased. Nickel-based casting preparation of high-temperature alloy material parts and components way, can be in the performance and processing mode, to meet the requirements of industrial production in various fields of raw materials. In addition, heat treatment is an indispensable process in the production of high-temperature alloys, can change the microstructure of the alloy to enhance the alloy’s heat resistance, corrosion resistance and other properties, in the process of nickel-based casting high-temperature alloys to prepare parts, the heat treatment process status is important.
The article introduces the development history of nickel-based casting high-temperature alloys and heat treatment technology and its impact on the structure and performance, describes the current status and trends in the development of heat treatment technology of nickel-based casting high-temperature alloys.
Nickel-based casting high-temperature alloy refers to nickel as the main component, casting method to directly prepare parts of high-temperature alloy materials. It has excellent high-temperature strength, fatigue stability and fracture toughness and good creep stability and other comprehensive mechanical properties, can be in a high-temperature environment for long-term safe operation, widely used in aerospace, automotive industry, gas turbine field engine turbine blades, the whole leaf disk, the magazine and other high-temperature components. With the development of aero-engine technology, the requirements for the performance of alloy materials have also increased dramatically. For the raw material performance enhancement as well as the improvement of the preliminary treatment work has become the main trend in China’s industrial production. Heat treatment is nickel-based casting high temperature alloys to improve the performance of the necessary process, by changing the morphology and distribution of the internal structure of the casting or change the chemical composition of the casting surface, you can improve the comprehensive mechanical properties of the casting, eliminating casting stress, or to improve the corrosion resistance of the casting. This paper mainly discusses the nickel-based casting high-temperature alloys and their heat treatment process technology research process, and summarizes and analyzes it, and looks forward to the future, in order to provide reference for the subsequent industrial production.
01The development history of nickel-based casting high temperature alloys
Nickel-based casting high-temperature alloy is an important part of the field of high-temperature alloys, in the production of various types of precision castings has a more prominent advantage, the main reason is that this material is high-temperature resistance, high oxidation and corrosion resistance properties. Early nickel-based high-temperature alloys are mainly deformation alloys, in the late 1950s, with the development of aero-engine technology, the engine turbine components of the temperature-bearing capacity of the requirements of more and more high temperature alloys, which puts forward the strength and use of higher temperature requirements. And enhance the strength of nickel-based high temperature alloys is to improve the alloy alloying degree, resulting in nickel-based high temperature alloys are more and more difficult to deform or even can not be deformed, can only be produced by casting process. In addition, with the development of engine blade design technology, the emergence of hollow air film hole cooling blade. This hollow blade with complex inner cavity, can only be produced by investment casting process. In this demand, domestic and foreign gradually developed a series of nickel-based casting high temperature alloy grades with good high temperature performance.
Nickel-based high-temperature alloys were first discovered in the United Kingdom in the early 1940s, and their use in jet aviation brought the importance of alloy properties to the attention of many industrial producers. Britain first produced the nickel-based alloy Nimonic75 (Ni-20Cr-0.4Ti) in 1941, and for a long time afterwards, developed countries such as the United States and the USSR also succeeded in developing similar alloy materials, while China also developed some alloy materials of the same nature in the late 1950s.
Study the development history of nickel-based casting high temperature alloys it is not difficult to find, it is roughly two directions of the research path: one is through the adjustment and combination of alloy composition, the study of different elements added than the impact of alloy performance, and then access to the optimal elements and composition ratio; two is through the nickel-based casting high temperature alloy production process, optimization of the production equipment and improvement, to enhance the alloy’s preparation technology. Such as the early 1950s, scientists through a large number of experimental research, research and development of the vacuum smelting process, the emergence and development of this process technology for the preparation of nickel-based casting high temperature alloys to provide technical aspects of the security; 1960s, developed countries through the research, put forward the melt casting process, the production of a large number of casting alloys with good high temperature performance. In the ensuing years, some single crystal casting high temperature alloys with better high temperature performance have been developed. With the development of aerospace engine technology, nickel-based casting high-temperature alloys also have higher requirements. Therefore, from the early 1950s to the end of the 1990s more than 40 years, with the continuous improvement of research and development capabilities, nickel-based casting high-temperature alloys performance and use of the temperature is also more and more high, the application field is more and more extensive.
02 Nickel-based casting high-temperature alloy strengthening mechanism and structural features
2.1 Solid solution strengthening
Nickel-based casting high-temperature alloys to enhance the performance of one of the methods is solid solution strengthening, which refers to aluminum, titanium, niobium, tantalum and other alloying elements can be formed with the matrix γ ′ phase alloy into the alloy, resulting in a certain lattice distortion, so as to enhance the strength of the alloy method. This phenomenon of strengthening a metal by incorporating a solute element to form a solid solution is called solid solution strengthening. This type of alloy has excellent oxidation and fatigue resistance properties, the most obvious advantage is the high structural stability, and good thermal plasticity. According to the above characteristics, nickel-based casting high-temperature alloys can be used to manufacture metal parts with large temperature variations, such as: fan blades of aircraft engines, turbine casing components.
2.2 precipitation strengthening
In recent years, precisionvast to improve the strength and performance of nickel-based casting high-temperature alloys of the method is mostly consistent, even if the difference in the addition of materials, there is little change. In the process of research to improve the strength and performance of the alloy, precisionvast will generally add a little precipitation strengthening elements in the alloy, through the heat treatment process from the alloy organization of the mother phase precipitation of the second phase (γ′, γ″, carbides, etc.), which in turn significantly improves the strength of the alloy. Typical γ′ phase in nickel-based casting high temperature alloys is Ni3Al or Ni3Ti, which is strengthened by the following two ways: one is to increase the content of Ai and Ti elements in the alloy to increase the number of γ′ phase; the second is to add elements such as Co, W, Mo and so on to improve the strength of the γ′ phase. Through the increase of some elements, the precipitated second phase can effectively inhibit the development and growth of metal material particles. Alloys with this strengthening method are mostly used to make high-temperature engine components, such as: aero-engine, gas turbine turbine blades and so on.
03Nickel-based casting high-temperature alloy heat treatment technology development
Heat treatment of nickel-based casting high-temperature alloys refers to a class of metal material heat treatment process for nickel-based high-temperature alloy products in the as-cast state, using the processing methods of heating, holding and quenching to achieve the desired microstructure and mechanical properties. It is of positive significance to study the effect of heat treatment on the microstructure of alloys in order to explore the mechanism of good heat treatment to improve the high-temperature properties of alloys. Among them, solid solution treatment and aging treatment are the main heat treatment processes. Solid solution treatment refers to the heat treatment process in which the excess phase in the microstructure of the alloy is fully dissolved into the matrix phase and then rapidly cooled to obtain a supersaturated solid solution. Solid solution treatment can strengthen the solid solution and improve the corrosion resistance of the matrix, at the same time can eliminate residual stresses in the matrix casting, generally as a preparatory heat treatment, for subsequent machining and subsequent aging treatment to prepare. Ageing treatment refers to the temperature interval in the precipitation of reinforcing phase heating and maintained for a period of time, so that the reinforcing phase of high-temperature alloys precipitated uniformly, thereby improving the strength of castings. In recent years, domestic researchers have also carried out more extensive and in-depth studies on the heat treatment process of nickel-based casting alloys. Yang Heyang on the new nickel-based single-structure high-temperature composites containing rare earth metals, explored the influence of different heat treatment methods on its structure and properties, using differential thermal analysis to determine the solid-phase line and liquid-phase line temperatures of the composite material, using metallographic test method to determine the initial melting temperature of the composite material, and finally formulated the heat treatment technology method of the composite material.
04 The latest progress of heat treatment technology of nickel-based casting high-temperature alloys
In recent years, with the nickel-based casting high-temperature alloy materials in industrial production in the wide range of applications, the heat treatment technology level of this material also continues to improve, the relevant scholars will be finite element numerical simulation methods and heat treatment process for the organic combination. The study of the heat treatment process parameters of the practical application of the specific impact, and according to the thermal processing experimental data to establish the precipitation temperature, relative to the high temperature alloy performance of the corresponding relationship between, and through the experimental process of a large number of data and experimental results, analytical demonstration of the construction of the heat treatment simulation database.
In recent years, Precisionvast has carried out research on heat treatment technology of high-temperature alloy engine parts for large ships, which has deeply integrated the finite element numerical simulation method and heat treatment technology, which is of great value in the control of process technology parameters and quality management of castings in actual manufacturing. At the same time, it also saves the time needed by craftsmen in data processing and program design, and promotes the development of nickel-based alloy heat treatment technology towards intelligence and high efficiency.
With the development of the concept of collaborative manufacturing, heat treatment process researchers are gradually and nickel-based casting high-temperature alloy developers to carry out cooperation, the heat treatment process and alloy composition design combined, in the nickel-based high-temperature alloy research and development of the initial period began to consider the best heat treatment process of the alloy, so that nickel-based casting high-temperature alloy to achieve the best performance.
05 Conclusion
In summary, this paper mainly for nickel-based casting high-temperature alloy development history and the current status of the heat treatment process line of discussion on the current stage of China’s nickel-based casting high-temperature alloy heat treatment technology development and development history made a detailed introduction to the development of the status quo as well as the specific direction of the research was elaborated. With the continuous improvement of China’s industrial production level in recent years, the relevant industries on the performance of alloy materials demand is also greatly enhanced, as can effectively improve the characteristics of nickel-based casting high-temperature alloys of metal heat treatment process, its advantages are obvious and can not be replaced by other processes, the need to carry out further exploration in the cutting-edge technology of heat treatment process.
