| The GH3625 super-alloy ingot has been produced by Vacuum Induction Melting(VIM) and Electro-Slag Remelting(ESR) processes. The hot deformation behavior of GH3625 alloy ingot, homogenization treatment process, the impact on homogenization treatment on hot deformation behavior of GH3625 alloy and effect of heat treatment on microstructure and mechanical properties of GH3625 alloy tubes were studied.The GH3625 super-alloy ingot has been deformed by Gleeble3800 thermal simulation machine, the hot deformation behaviors during temperature at 800~1200℃ and strain rate at 0.01~10s-1 were investigated. The results show that there is a significant peak value in the true stress-strain curve of the as cast GH3625 alloy, and the peak stress increases with the increase of strain rate and the decrease of the deformation temperature. During the hot deformation process, the alloy showed obvious recrystallization, and the recrystallization microstructure was uniform. By establishing the constitutive equation and hot processing map of as cast GH3625 alloy we can obtained that activation energy is Q=370.87KJ/mol and the optimum processing area temperature is about 1180℃, and the strain rate is less than 0.1s-1.The microstructure and element segregation behavior of as cast GH3625 alloy were studied. It was found that the GH3625 alloy ingot has obvious dendrite structure. The primary dendrite arm spacing was 162.5μm, and the secondary dendrite arm spacing was 27.1μm. GH3625 alloy ingot are rich presence of Nb, Cr, Mo, Al, and other elements of the Laves phase as well as a small amount of carbide MC. The elements such as Nb, Mo, Ti, Al and other elements are enriched between the dendrite, Cr enriched in the dendrite. The segregation degree of different elements is Nb>Mo>Ti>Al>Cr. In the homogenization process, with the homogenization temperature and the time prolong the extension segregation elements gradually spread evenly. After homogenization treatment, the segregation phase of the dendrites gradually decreases, and the carbide change from the block into granules.The effect of homogenization treatment on the hot deformation behavior of as cast GH3625 alloy was researched. The results show that the dendrite elimination of as cast GH3625 alloy after two stage homogenization treatment. The activation energy of isothermal compression deformation for GH3625 alloy is Q=652.22KJ/mol. When the compression rate is 60%, the power dissipation efficiency reaches a maximum value of 0.48 during hot compression at 1000 ℃ and 1200 ℃, strain rate of 0.01s-1. The GH3625 alloy is completely dynamic recrystallization during hot compression temperature of 1100 ℃ ~ 1200 ℃. When the power dissipation is less than 0.28, the recrystallized grains are fine and uniform, when it reaches peak efficiency 0.48, the recrystallized grains will grow up. The suitable processing area temperature of GH3625 alloy is 1180℃, and the strain rate is 0.01s-1.Hot extrusion pipe GH3625 alloy was heated treatment under different temperature, and the effect of heat treatment on its microstructure and properties were investigated. The results show that heat treatment temperature have a greatly effect on grain growth. With the heat treatment temperature increased, the grain growth is in a different degree, at the same time, the snow-shaped of Pt2 Mo style Ni2(Cr,Mo) phase is formed, and the phase distribution is also changed. The hardness value and grain size of GH3625 alloy tube are in agreement with Hall-Patch relation. Also the tensile strength of GH3625 alloy is decreased, while the percentage elongation after fracture increase with increasing temperature. Before and after the heat treatment of GH3625 alloy, the fracture type of GH3625 alloy includes two kinds: dimple fracture and the fracture along crystal. |
PDF Full Text Request