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Classification and Characteristics of Superalloy Materials
Release time:
2022-01-10
1. Classification of high temperature alloys
Superalloys have excellent thermal strength, thermal stability and thermal fatigue resistance. There are many types of high-temperature alloys, generally based on iron, nickel, and cobalt, adding multiple alloying elements to obtain high-temperature alloys for different purposes. Commonly used additive elements are cobalt, chromium, tungsten, molybdenum, niobium, tantalum, titanium, aluminum, vanadium, hafnium, boron or zirconium.
High temperature alloys are divided into different types of high temperature alloys according to different matrix elements, strengthening methods and production processes.
1) Classification by matrix elements
According to the different matrix elements, high temperature alloys can be divided into the following types.
(1) iron-based high-temperature alloy (also known as heat-resistant steel). It uses iron as the main component (>10%), and most of it is easily based on Fe-Ni-Cr, and is formed by adding other alloying elements. Iron-based superalloys contain large amounts of iron to stabilize the austenitic matrix. Generally, high-temperature alloys containing 25% ~ 60% nickel and 15% ~ 60% cold iron are turned into iron-nickel-based high-temperature alloys, such as GH1140,GH2132,GH2135,GH761,GH901,K214, etc. (the first Arabic numeral after GH and K is the classification number, and 1 means solid solution strengthened iron-based alloy; 2 means precipitation (aging) strengthened iron-based alloy; 3 means solid solution strengthened nickel-based alloy; 4 represents a precipitation-strengthened nickel-based alloy; 5 represents a solid solution-strengthened cobalt-based alloy; 6 represents a precipitation-strengthened cobalt-based alloy; 7 represents a solid solution-strengthened chromium-based alloy; 8 represents a precipitation-strengthened chromium-based alloy; the following two or three digits are the number of the alloy).
(2) nickel base high temperature alloy. It is nickel as the main component, nickel content is greater than 45%, generally Ni-Cr solid solution as the matrix, formed by adding alloying elements. Nickel-based high-temperature alloys include wrought nickel-based high-temperature alloys and cast nickel-based high-temperature alloys. There are many alloys belonging to this category, such as GH4033,GH4133,GH4037,GH4049,GH4169,GH220,GH738,K403,K405,K417,K417G,K419, etc.
(3) cobalt base high temperature alloy. Cobalt-based superalloys can be used at high temperatures of 700 to 1050°C. It is mainly composed of cobalt, and its typical representative is K610, which contains more than 58% cobalt. Due to the high price of cobalt and the shortage of resources, it is rarely used by domestic and foreign troops. The existing brands are K640, K644, GH188, etc.
In addition, there are molybdenum-based high-temperature alloys, niobium-based high-temperature alloys, titanium-based high-temperature alloys, etc., but have not been widely used.
2) Classified by strengthening method
High temperature alloys can be divided into the following types according to different strengthening methods.
(1) solid solution strengthened high temperature alloy. Solid solution strengthening is the basic strengthening means of high temperature alloys. The main alloying elements used in this alloy are Co, Cr, Mo, W, Nb, Ta, etc. China has successfully developed a series of W, Mo, Nb and other elements to strengthen the nickel-based and iron-based high-temperature alloys, such as GH1016,GH3039,GH1140,GH3044 and so on.
(2) precipitation strengthening (age hardening) high temperature alloy. The main alloying elements used in this alloy are Al, Ti, Ta, Hf(γ′, γ″), C, Cr, W, Mo, V, Nb, Ta, Hf (carbide), etc. Most of the alloy to Ni3Al type γ′ phase as the main strengthening phase, there are Ni3Nb type γ″ phase as the strengthening phase (such as GH4169 high temperature alloy). In cobalt-based and a few iron-based superalloys (such as GH2036), there are also carbides as strengthening phases. Second phase strengthening plays a very important role in high temperature alloys, such as GH2302,GH4049,K214,K401, etc.
(3) dispersion strengthened high temperature alloy. They are generally Y2O3, ThO2, HfO2 and ZrO2 and other oxides as the second phase dispersion guidance and highly dispersed in the alloy, in order to achieve the purpose of strengthening, such as MGH754, MA6000E, etc.
3) Classification by production process
High temperature alloys are divided into the following types according to different production methods.
(1) deformation of high temperature alloy. Such high temperature alloys include maraging alloys, solid solution strengthened austenitic alloys and precipitation hardened austenitic alloys. They are obtained by solid solution strengthening, precipitation hardening and strengthening grain boundaries and other methods of high temperature performance, common deformation of high temperature alloy GH1015, GH2036, GH3128, GH4133 and so on.
(2) casting high temperature alloy. When the alloy composition and structure are complex, the plasticity is not high, can not withstand deformation, the precision casting method can be used to shape it. Such alloys include iron, nickel, and cobalt-based alloys, such as K211, K417, and K640.
(3) directional solidification of high temperature and. The alloy is melted in a vacuum induction furnace, remelted in a directional solidification furnace, and cast into directional solidification castings, such as DZ3, DZ22, DZ4, DZ38G, DZ202, etc.
(4) single crystal high temperature alloy. This kind of alloy is melted in a vacuum melting furnace master alloy, remelted in a vacuum induction furnace, manufactured by investment precision casting method and directional solidification seeding method, such as DD3, DD8.
(5) powder high temperature alloy, Gao Lei alloy is the alloy title powder, by hot isostatic pressing forming, and then forged, such as FG02-01(FGH95). This high-temperature alloy is a gamma-phase precipitation-strengthened nickel-based high-temperature alloy, gamma-phase content of about 50% (volume), uniform organization, fine grain, high yield strength, good fatigue resistance.
2. Material properties of high-temperature alloys
The physical and mechanical properties of some commonly used high-temperature alloys in China are shown in Table 2-3:
The material characteristics of high-temperature alloys related to grinding processing are shown below.
(1) The matrix of high temperature alloy is Ni-Cr, Fe-Ni-Cr or Co-Cr-Ni austenite, which contains many high melting point alloy elements, such as Fe, Cr, Co, Ni, V, Mo, W, Nb, Ta, etc. The interactions between alloying elements and the matrix are complex. Due to the combination of solid solution strengthening, co-lattice phase precipitation strengthening, carbide strengthening and grain boundary control, the mystery of the austenitic alloy curse is formed, which greatly improves the mechanical properties of high-temperature alloys and increases the plastic deformation layer during grinding.
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