High-end metal structure material, high temperature resistance and corrosion resistance
High temperature alloy refers to a class of metal materials based on iron, nickel and cobalt that can work for a long time under high temperature above 600 ℃ and under certain stress. High-temperature alloys have higher high-temperature strength, good oxidation and corrosion resistance, good fatigue properties, fracture toughness and other comprehensive properties. The biggest characteristic of superalloys is not that their absolute melting point is very high, but that they still have good characteristics at high temperatures.
High-temperature alloys are high-end metal structural materials, and the localization of high-temperature alloys has long been a “jam neck” problem in related applications. In the "Twelfth Five-Year Development Plan for New Materials Industry" released in 2012, high-end metal structural materials including high-temperature alloys were listed as one of the six key development areas of the new materials industry.
A series of policies have subsequently been issued to support the research and development and production of high-temperature alloys. Among them, "Made in China 2025" proposes to vigorously promote the development of the new material industry, with six new materials including high-end metal structural materials as the development focus, and clearly strive to make China's new material industry has entered the ranks of world-class powers.
High temperature alloy has the characteristics of high temperature resistance and corrosion resistance. In high temperature environment, the material will accelerate degradation, and it is easy to cause tissue instability, deformation and crack growth under the action of temperature and stress, and oxidative corrosion on the surface of the material. The high temperature alloy has high temperature resistance and resistance Corrosion and other properties mainly depend on its chemical composition and organizational structure.
Taking GH4169 nickel-based deformed superalloy as an example, GH4169 matrix is Ni-Gr solid solution, containing Ni mass fraction above 50%, can withstand high temperature around 650 ℃, similar to American brand Inconel718, alloy consists of γ matrix phase, δ phase, carbon The GH4169 alloy's chemical elements and matrix structure show its strong mechanical properties, yield strength and tensile strength are several times better than 45 steel, and the plasticity is better than 45 steel. The stable lattice structure and a large number of strengthening factors constitute its excellent mechanical properties.
In addition to the main metal components, superalloys also have requirements for trace elements. Also taking GH4169 nickel-based deformed superalloy as an example, the requirements for impurity elements such as B, Mg, Mn, Si, P, S, Cu, Ca, Bi, Sn, Pb, Ag, Se are very strict.
High-temperature alloy processing is difficult
The machining surface integrity of the material plays a very important role in the performance of the performance, and the high-temperature alloy micro-hardening item has high hardness and severe work hardening, and has high shear stress and low thermal conductivity, cutting force and temperature Due to its high characteristics, problems such as low surface quality and severe tool damage often occur during processing.