Test materials for the test material is the use of vacuum induction + vacuum consumption of the smelting process preparation Φ240mm GH710 alloy ingot, the free forging a single pull for Φ210mm forging sticks, chemical composition of raw materials see. The raw material has low density organization, no other metallurgical defects visible to the naked eye, but the grain structure is relatively coarse, and some large grains have residual dendrites and microstructure. Due to the high degree of alloying of GH710 alloy, the segregation of elements in the ingot is very easy, and the as-cast microstructure has serious dendrites. The dendrites are rich in large amount of primary γ 'and MC phases, which make the ingot hot deformation performance poor Produce forged cracks. The existence of coarse and residual dendrites in bares is mainly due to the insufficient amount of forged billet deformation.
Test method The alloy isothermal forging experiment was carried out on a 6300 kN hydraulic press. The mold material was cast high temperature alloy and the billet heating temperature was 1100 ℃. The isothermal forging turbine disk forging after air cooling standard heat treatment: electric cookware press 1170 ℃ × 4h, air cooling + 1080 ℃ × 4h, air cooling +845 ℃ × 24h, air cooling +760 ℃ × 16h, air cooling. The metallographic sample was prepared according to the conventional procedure, and the etching agent was 50 ml of hydrofluoric acid + 20 ml of hydrochloric acid + 10 ml of hydrogen peroxide.
The effect of forging process on the microstructure and residual dendrites of the GH710 alloy bar is effectively eliminated. At the same time, the alloy has good formability, and the alloy deformation experiment is carried out by the isothermal forging process. The heating temperature of the blank is 1100 ℃, deformation of 50% and 70% respectively.
GH710 alloy in the isothermal forging deformation, with good plasticity, a deformation of 50% and 70%, the appearance of good biscuits, there is no forging cracks. After the alloy is deformed by isothermal forging, the microstructure is obviously improved, and the coarse grain structure in the bar is effectively broken, and the alloy is completely recrystallized. Billet parts of the deformation of uniform, no deformation dead zone. Its microstructure.
The isothermal forging cake was heat treated by standard four sections. The sample was cut and tested for its room temperature tensile, 980 ℃ smooth and lasting performance and 815 ℃ notch durability. After the isothermal forging deformation of the GH710 alloy with low magnification, the billet forging has good room temperature strength and high temperature durability, and the properties of the parts are very uniform and the dispersion of the performance results is very small.
Isothermal forging GH710 alloy uniform structure, low magnification and microstructure testing and analysis did not find more than 1mm thick grain; 815 ℃ gap lasting life of 114h did not pull off, far higher than the standard ≥ 30h technical requirements; 980 ℃ smooth lasting life of 80h or more, but also far higher than the standard ≥ 30h technical requirements.
The isothermal forging turbine disk was used to verify the rationality of the GH710 alloy turbine disk. The isothermal forging process was studied. The isothermal forging process was successfully applied to the development of GH710 alloy turbine die forging. The quality of GH710 alloy Φ240mm turbine plate isothermal forging die forging was simulated, and the microstructure and properties of the forging were tested and analyzed.
GH710 alloy isothermal forging turbine disk forging, fine grain, forging parts of the organization uniform, forging flow line along the forging profile continuous distribution, no deformation dead zone, forging low magnification as shown. Turbine disk forging hub, spoke and rim parts of the grain size uniform fine, in the grain boundary with γ 'phase precipitation, forging parts of the microstructure as shown.
The mechanical properties of the isothermal forged turbine discs are carried out after the four-stage standard heat treatment of the GH710 alloy isothermal forged turbine disk forging. The mechanical properties of the isothermal forged turbine disk forgings are fully satisfied according to the literature <5> The technical requirements. The room temperature tensile properties σb to 1200MPa, 890MPa higher than the standard requirements of more than 300MPa; 815 ℃ gap lasting life of 64150h sample has not yet pulled off; and 980 ℃ smooth and lasting performance is beyond the technical requirements of ≥ 30h, According to the experimental site, increase the test stress to force the specimen to pull off. See also.
(1) isothermal forging process can effectively improve the deformation properties of GH710 alloy, refine the grain structure, improve the mechanical properties. (2) the use of isothermal forging process can be obtained complete appearance, fine grain, uniform performance of the turbine plate and other die forging. (3) isothermal forging process is the preparation of GH710 alloy thin crystal disk ideal forming process.
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