Nickel-based superalloy disk is a key component of gas turbine.The long-term aging microstructure evolution has a great influence on the service life of disk.After standard heat treatment,samples of large-sized nickel-based superalloy 4725FC1(with a composition similar to IN718)were taken and subjected to long-term aging at temperatures of 620℃/650℃for different durations,with a maximum of 10 000 hours.Research has shown that the main form of carbides in nickel-based superalloy 4725FC1 is MC type,and the size of carbide is less than 10 μm.The grain size of the alloy aged at 620℃and 650℃for 10 000 h has no obvious change.With the increase of aging time,the δ phase on the grain boundary increases significantly and shows a continuous trend,and the number of needle-like δ phases in the crystal also increases.After aging at 650℃for 10 000 h,white Nb-rich,Cr-rich and Mo-rich phase will appear in the crystal,which will reduce the solid solubility of the matrix and affect the mechanical properties of the alloy.Long-term aging can increase the hardness of the alloy to a certain extent,but the increase is not large.
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