| The important application value of nickel-base superalloys, serving as main material of vane for aero engine and gas turbine, is self-evident. Therefore, the study on the component, manufacturing process, microstructure and properties of nickel-base superalloys, which demonstrate excellent combination properties, is becoming more and more urgent. K465 alloy has an ablity of bearing elevated temperatue, and so has an extensive foreground in national defence, spaceflight and aviation. The research on K465 alloy has vital theoretical and practicable sense.The present paper developed and made researches of master alloy melting, casting, melt superheating treatement and micro-alloying on K465 alloy and made the investigation on the segregation, gas content, microstructure and mechanical properties of K465 alloy through the tests and analyses methods by using XRD, SEM, EDS, graph analysis apparatus, etc. Thermodynamics model of nitrogen in nickel-base alloy was established and the behavior of nitrogen was analysed. The effects of magnesium and cerium on the microstructure and mechanical properties were studied. The main results of research were as follows:1. The melting technology was confirmed, the chemical compostion and mechanical properties were quite stable in the alloy through the melting technology confirmed in present paper.2. The results showed that the pouring temperature and shell mould temperature had obvious effect on the microstructure and properties of K465 superalloy. The grain size, secondary arm andγ'phase reduced with the descending of the pouring temperature or the shell mould temperature. The carbide tended to have script-like shape with the increment of the pouring temperature or the shell mould temperature. The test analysis of mechanical properties showed that the alloy would attain preferable properties with suitable pouring and shell mould temperature.3. The research results of melt superheating treatment were as follows:1) The melt superheating treatment of melt below 1750℃had little effect on the chemical composition of the alloy. But the melt superheating treatment above 1750℃caused a significant decrease in C, Al, Ti and Cr content. 2) The melt superheating treatment had an obvious effect on the content of nitrogen. Melt superheating treatment promoted denitrogenation process of the nickel-base superalloy. Though at the higher temperature of melt treatment, there was an increase of nitrogen content. The approximate theoretical model was established. In this study, at the lower temperature of melt treatment, the measured value of nitrogen was anastomosed to the model. However, the melt superheating treatment above 1790℃caused an increment in nitrogen content, which was resulted from the action of variation of melt structure.3) The melt superheating treatment had little effect on the segregation of Cr, Co, Al and Ni. The segregation of Ti and Nb decreased with the increasing of melt superheating temperature. Howerer, the segregation of Mo and W decreased followed by an increment with the increasing of melt superheating temperature.4) Without any melt superheating treatment, the grain was equiaxed, the morphology of carbide tended to have big blocky appearance. With the increasing of melt superheating temperature, the size of grain increased gradually and the MC carbide changed from blocky appearance to script-like shape morphology. When the melt superheating treatment temperature was above 1760℃, the size of grain refined gradually and the script-like carbide presented tiny granular shape and distributed evenly. When the melt superheating treatment temperature was below 1750℃, the melt superheating treatment had little effect on the volume percent of primary MC carbide and (γ+γ') eutectic. However, when the melt superheating treatment temperature was above 1750℃, the volume percentage of MC carbide and (γ+γ') eutectic decreased gradually due to the melting loss of alloy elements.5) The variation of melt treatment temperature had little effect on the ultimate tensile strength, yield strength at room temperature, and the plastic properties had a certain extent of increment. With the further increment of melt treatment temperature, the plastic properties had an obvious decrease. The room strength and plastic properties got an optimized matching when the temperature was between 1750℃and 1760℃. When the melt treatment temperature was below 1750℃, with the increase of temperature, the creep-rupture life and creep-rupture plastic properties had an obvious increment. Under the condition of 975℃/230 MPa, the stress-rupture life and plastic properties got an optimized matching when the temperature was between 1650℃and 1760℃. When the melt treatment temperature was avove 1760℃, the stress-rupture life and plastic properties had a significant decrease. 4. The research findings on the study of Mg, Ce micro-alloying showed that with the increase of Mg content, the carbide changed to tiny blocky morphology, the size ofγ'precipitate decreased and had a cubic shape. With the further increase of Mg content (up to 0.03%, mass fraction), the carbide changed to script-like shape and the size ofγ' precipitate increased. The content of Mg had no significant effect on the mechanical properties of room temperature. With the increment of Mg content, the stress-rupture life and plastic properties under the condition of 975℃/230 MPa had a significant increase, the suitable addition of Mg was 0.02% mass fraction. With the further increment of Mg content, the stress-rupture life and plastic properties had an obvious decrease.In the range of this study, the content of Ce had no obvious effect on the microstructure and room temperature mechanical properties of K465 alloy. The MC carbide tended to have a script-like appearance and the morphology ofγ'precipitates had little change. And there was low-melting-point phase which was rich in Ce in the K465 alloy. Under the condition of 975℃/230 MPa, due to the existence of low-melting-point phase which was rich in Ce and increment of shrinkages, the stress-rupture life and plastic properties were kept at a low level all along at the range of 0.01%～0.03%(mass fraction) Ce addtion. In this paper, the added Ce could not strengthen the alloy.The research findings on the cast showed that the adoption of split pattern and combined clamp ensured the uniformity and the dimensional precision of turbine nozzle blades, achieved the precise wax cast of turbine nozzle for investment casting. The modification of pouring system and casting technique avoided the microporosity and thermal fragmentation, ensured the high metallurgy quality of cast, contributed to obtain an acceptable cast of turbine nozzle. Moreover, the cast got a good performance in the trail run.
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