Superalloy refers to a kind of metal material based on iron, nickel and cobalt, which can work for a long time at high temperature above 600℃ and under certain stress. It has high high temperature strength, good oxidation and corrosion resistance, good fatigue performance, fracture toughness and other comprehensive properties. Superalloy is a single austenite structure, which has good structural stability and reliability at various temperatures.

Based on the above performance characteristics, and the high alloying degree of superalloy, also known as "superalloys", is an important material widely used in aviation, aerospace, petroleum, chemical industry and ships. According to the matrix elements, superalloys can be divided into iron-based, nickel-based and cobalt-based superalloys. Generally, the service temperature of high-temperature alloy can only reach 750~780℃. For heat-resistant parts used at higher temperatures, alloys based on nickel and refractory metals are used. Nickel-based superalloys occupy a particularly important position in the whole field of superalloys, which are widely used to manufacture the hottest parts of aviation jet engines and various industrial gas turbines.

Production process:

1, casting metallurgical process

Various advanced casting manufacturing technologies and processing equipment are constantly being developed and improved, such as thermal control solidification, fine grain technology, laser forming repair technology, wear-resistant casting technology, etc. The original technical level is constantly improved and improved, thus improving the quality consistency and reliability of various high-temperature alloy casting products.

High temperature alloys containing little or no aluminum and titanium are generally smelted by electric arc furnace or non-vacuum induction furnace. When high-temperature alloys containing aluminum and titanium are melted in the atmosphere, the burning loss of elements is difficult to control, and more gases and inclusions enter, so vacuum smelting should be adopted. In order to further reduce the content of inclusions, improve the distribution of inclusions and the crystal structure of ingots, a duplex process combining smelting and secondary remelting can be adopted. The main means of smelting are electric arc furnace, vacuum induction furnace and non-vacuum induction furnace; The main means of remelting are vacuum consumable furnace and electroslag furnace.

Forging cogging can be used for solid solution strengthened alloys and alloy ingots with low aluminum and titanium content (the total amount of aluminum and titanium is less than 4.5%); Alloys with high aluminum and titanium content are generally extruded or rolled into billets, and then hot rolled into products, and some products need further cold rolling or cold drawing. Alloy ingots or cakes with larger diameter need to be forged by hydraulic press or fast forging hydraulic press.

2. Crystalline metallurgical process

In order to reduce or eliminate grain boundaries perpendicular to the stress axis and porosity in cast alloys, directional crystallization technology has been developed in recent years. In this process, the grains grow along a crystallization direction during the solidification of the alloy to obtain parallel columnar crystals without transverse grain boundaries. The first technological condition to realize directional crystallization is to establish and maintain a large enough axial temperature gradient and good axial heat dissipation conditions between liquidus and solidus. In addition, in order to eliminate all grain boundaries, it is necessary to study the manufacturing process of single crystal blades.

3. Powder metallurgy process

Powder metallurgy process is mainly used to produce precipitation strengthened and oxide dispersion strengthened superalloys. This process can make the cast superalloy which can not be deformed generally obtain plasticity or even superplasticity.

4, strength improvement process

Solution strengthening: adding elements (chromium, tungsten, molybdenum, etc.) different from the atomic size of the matrix metal will cause the lattice distortion of the matrix metal, adding elements (such as cobalt) that can reduce the stacking fault energy of the alloy matrix and adding elements (such as tungsten, molybdenum, etc.) that can slow down the diffusion rate of the matrix elements to strengthen the matrix.

Precipitation strengthening: The second phase (γ′, γ″, carbide, etc.) is precipitated from supersaturated solid solution through aging treatment to strengthen the alloy. The γ' phase is the same as the matrix, which is a face-centered cubic structure, and its lattice constant is similar to that of the matrix, and it is coherent with the crystal. Therefore, the γ' phase can be uniformly precipitated in the matrix as fine particles, which hinders the dislocation movement and has a significant strengthening effect. γ' phase is A3B intermetallic compound, where A represents nickel and cobalt, and B represents aluminum, titanium, niobium, tantalum, vanadium and tungsten, while chromium, molybdenum and iron can be both A and B.. The typical γ′ phase in nickel-based alloys is Ni3(Al,Ti). The strengthening effect of γ' phase can be enhanced by the following ways.