| In this dissertation, a single crystal superalloy with different contents of Ru addition (0, 1.5, 3.0 wt.%) was employed to study the influence of Ru addition on the the as-solidified microstructure, structural evolution during heat treatment and long term aging, stress rupture properties and the effect of different withdrawing rate (2mm/min, 6mm/min, 10mm/min) on the solidification microstructure of single crystal superalloys by using scanning electron microscope (SEM), transmission electron microscope (TEM), differential scanning calorimetry (DSC), energy dispersive spectroscopy (EDS) and some other research methods. The main conclusions can be drawn as follows:All the three kinds of alloys with different Ru content were solidified with dendritic morphology. In the as-solidified microstructure of alloy with 3% Ru content, besidesγ/γ′eutectics exist in the interdendritic region, some NiAl basedβphase with blocky morphology formed there. The primary dendrite arm spacing decreases with the increment of Ru content, while the volume fraction ofγ/γ′eutectics decreases with the increasing of Ru addition.With the increasing of Ru content in the alloy, its liquidus have little change. while the solidus decreases a little, the solidification range become a little wider. The investigation of segregation behavior for alloying elements showed that Ru is apt to segregation to dendritic core region. With 1.5% Ru addition, the accumulation ofγ′forming elements like Al, Ta, etc. towards dendrite core become enhanced and refractory element like Re towards dendrite core become enhanced. When further increase Ru addition to 3%, the prior segregation trends of Al as well as W, Re become more significant.All the kinds of alloys with different withdrawing rate were solidified with dendritic morphology. With the increase of withdrawal rate, the microstructures of single crystal alloy transforms from coarse dendrite to fine dendrite. With the increase of withdrawal rate, the size of theγ′particles decreases, segregation of alloying element between dendrite and interdendritic region tends to be reduced and the volume fraction ofγ/γ′eutectic and NiAl-basedβphase tend to decreases.After fully heat treatment, with the increase of ruthenium content, the size ofγ′phase deceases. During the long term aging at 1100℃, with the increasing of Ru content, the tendency to form raft enhanced. Ru can suppress the precipitation of TCP phases effectively.In the stress rupture tests,the stress rupture life increase with the increment of Ru content at 1100℃/180MPa. However, at 1000℃/310MPa, the Ru free alloy and 3% Ru contented alloy possess similar rupture lives, while the alloy with 1.5% Ru has an apparently lower stress rupture life and higher the elongation.
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