Nickel-based high-temperature alloys (nickel-based alloys) were developed in the late 1930s. Britain first produced nickel-base alloy Nimonic 75(ni-20cr-0.4 Ti) in 1941; Nimonic 80(ni-20cr-2.5 ti-1.3 Al) was developed in order to increase the creep strength and add aluminum. The United States in the mid-1940s, the Soviet union in the late 1940s, China also developed the nickel base alloy in the mid-1950s. The development of nickel-based alloys consists of two aspects: improvement of alloy composition and innovation of production process. In the early 1950s, the development of vacuum smelting technology created conditions for the refining of nickel-base alloys containing high aluminum and titanium. The initial nickel-based alloys are mostly deformed alloys. Late 50 s, because of the increase in working temperature of the gas turbine for high temperature alloy has a higher strength, but the strength of the alloy is high, it will be difficult to deformation, even not deformation, so adopt revestment precision casting technology, developed a series of casting alloy has good high temperature strength. In the mid - '60s, we developed better directional crystallization and single crystal high-temperature alloy and powder metallurgy high temperature alloy. In order to meet the needs of ships and industrial gas turbines, a series of high chromium nickel base alloys with good corrosion resistance and stable structure have been developed since the 1960s. In the period from the early 1940s to the end of the 1970s, the working temperature of the nickel base alloy increased from 700 to 1100, with an average increase of about 10 per year.
Nickel base high temperature alloy is the most widely used. The main reason is that one is that the nickel base alloy can dissolve more alloy elements and maintain good stability of the tissue. Type 2 it is to form a coherent and orderly A3B intermetallic compound gamma [Ni3 (Al, Ti)] phase as a strengthening phase of the alloy is effectively improved, compared with high temperature iron base alloy and high temperature strength of cobalt base superalloy higher; Third, the chromium nickel base alloy has better anti-oxidation and anti-gas corrosion resistance than iron base alloy. The nickel base alloy contains more than ten elements, among which Cr is mainly anti-oxidation and anticorrosion, and other elements are mainly strengthened. According to their reinforcement, the method can be divided into: solid solution strengthening elements, such as tungsten, molybdenum, cobalt, chromium and vanadium; Precipitation strengthening elements, such as aluminum, titanium, niobium and tantalum; Grain boundary strengthening elements such as boron, zirconium, magnesium and rare earth elements.
Casting: it is usually used to ensure the composition and control of gas and impurities in the vacuum induction furnace, and to make parts by vacuum remelting and precision casting.
Heat treatment: need to have heat treatment deformation alloy and some casting alloy, including solid solution treatment, middle and aging treatment, Udmet 500 alloy, for example, its heat treatment system is divided into four sections: solid solution treatment, 1175 ℃, 2 hours, air cooling; Intermediate treatment, 1080, 4 hours, air cooling; An aging treatment, 843 ℃, 24 hours, air cooling; Secondary aging treatment, 760 ℃, 16 hours, air cooling. To obtain the desired organizational status and good comprehensive performance.
