Nimonic 75 (N06075) 2.4951 nickel-based high-temperature alloy
Nimonic75
British brand: Nimonic75 nickel-based high-temperature alloy
US grade: UNS N06075
German brand: 2.4951
Nimonic75 (N06075) Overview:
Nimonic 75 (N06075) nickel-based alloy is a nickel-chromium alloy with extremely low titanium and iron content and excellent high-temperature properties. The addition of elements (chromium, tungsten, molybdenum, etc.) that are different in atomic size from the base metal in this alloy causes distortion of the base metal lattice. The addition of elements (such as cobalt) that can reduce the stacking fault energy of the alloy matrix and the addition of elements that can slow down the diffusion of base elements Rate elements (tungsten, molybdenum, etc.) to strengthen the matrix.
1. Precipitation strengthening: Nimonic 75 precipitates the second phase (γ', γ", carbide, etc.) from the supersaturated solid solution through aging treatment to strengthen the alloy. The γ' phase is the same as the matrix, and both have a face-centered cubic structure. The array constant is close to the matrix and coherent with the crystal, so the γ phase can precipitate uniformly in the form of fine particles in the matrix, hindering dislocation movement and producing significant strengthening effects. The γ' phase is an A3B type intermetallic compound, A stands for nickel and cobalt, B stands for aluminum, titanium, niobium, tantalum, vanadium, and tungsten, while chromium, molybdenum, and iron can be either A or B. The typical γ' phase in nickel-based alloys is Ni3(Al,Ti) . The strengthening effect of γ' phase can be enhanced through the following ways:
(1), increase the number of γ' phases;
(2) Make the γ' phase and the matrix have an appropriate degree of mismatch to obtain the strengthening effect of coherent distortion;
(3) Add elements such as niobium and tantalum to increase the anti-phase domain boundary energy of the γ' phase to improve its ability to resist dislocation cutting;
(4) Add elements such as cobalt, tungsten, and molybdenum to improve the strength of the γ' phase. The γ" phase has a body-centered tetragonal structure, and its composition is Ni3Nb. Due to the large mismatch between the γ" phase and the matrix, it can cause a large degree of coherent distortion, allowing the alloy to obtain a high yield strength. But above 700℃, the strengthening effect is significantly reduced. Cobalt-based superalloys generally do not contain γ phase, but are strengthened with carbides.
2. Grain boundary strengthening: At high temperatures, the grain boundaries of the alloy are the weak links of Nimonic 75. Adding trace amounts of boron, zirconium and rare earth elements can improve the grain boundary strength. This is because rare earth elements can purify grain boundaries, and boron and zirconium atoms can fill grain boundary vacancies, reduce the grain boundary diffusion rate during creep, inhibit the aggregation of grain boundary carbides and promote the spheroidization of the second phase of grain boundaries. In addition, adding an appropriate amount of hafnium to the casting alloy can also improve the strength and plasticity of the grain boundaries. Heat treatment can also be used to form chain-like distributed carbides at grain boundaries or to create curved grain boundaries to improve plasticity and strength.
Corresponding trademarks: W.NR 2.4951 W.NR 2.4630 UNS N06075 AWS 032
Applicable standards: BS HR 5 BS HR 504
Nimonic 75 is a nickel-chromium alloy with outstanding corrosion and heat resistance.
