The Effect Of PressΜre On The MicrostrΜctΜre And Properties Of The Casting Alloy Of K418 With Different Thickness Of Thin Plate

Nickel-based superalloys have important application value as the main materials for service in various aviation,aerospace engines and gas turbines.Research on the casting process of nickel-based superalloys with excellent overall performance has important application value.K418 is a γ-phase precipitate-enhanced nickel-base cast superalloy with good creep strength,thermal fatigue properties and oxidation resistance,and has been widely used in aerospace,marine,automotive and other fields.It is of great theoretical and practical significance to carry out research on the forming process of K418 casting alloys.This paper takes K418 nickel-based superalloy as the research object,using ProCAST casting simulation software to simulate the investment casting process of K418 with different thickness under different environmental pressures.The size of the sheet is 400 x 300 and the thickness is 3mm,5mm,7mm,and 9mm,respectively.According to the results of the simulation experiment,under different environmental pressures,vacuum induction melting furnace was used to cast different thickness of the wall panels.The tensile specimens were subjected to solution heat treatment at 1180℃ + 2h + air cooling 960℃ + 16 h + air cooling.Combined with metallographic microscope,scanning electron microscope(SEM),electronic balance,micro-hardness tester,electronic universal testing machine and other analysis and testing methods,the influence of environmental pressure on the microstructure and properties of K418 alloys with different thicknesses was studied.The ProcAST casting simulation software was used to simulate the filling and solidification process of K418 at ambient pressure of vacuum and 101.325 kPa.Castings use investment castings under vacuum and gravity casting modules under a standard atmospheric pressure.The simulation results show that under two different environmental pressures,the castings can be fully filled with shells;the same thickness of the wall cooling sequence is consistent,the edge of the wall first solidified,then the middle of the wall,and finally close to the crevice runner The final solidification of the site;different thickness of the wall,the smaller the thickness of the wall,the faster the cooling rate.Under vacuum,the solid phase rate of the casting can reach more than 80% when the solidification time is 800 s.When the solidification time of the siding is 600 s,the solid fraction of the casting can reach more than 80%.It shows that the cooling rate of the casting is faster than that of the vacuum.The wall thickness of the wall plate with different thickness is most likely to cause shrinkage shrinkage and shrinkage defects.The casting was cast in a vacuum induction furnace at a pressure of vacuum and 101.325 kPa ambient pressure.The results show that for the same thickness castings,the pressure effect of the casting structure is more dense,and the Vickers hardness is increased;the pressure effect has the most significant effect on the microstructure of the 5 mm wall panels,followed by the 7 mm wall panel microstructure morphology,and the 3 mm and 9 mm organizational morphology.The effect is not significant;the effect of pressure on the density of the middle part of the wall plate with a smaller thickness is more significant,and it also has an effect on the area close to the gap.After the heat treatment,the room temperature tensile properties do not show regular changes,the elongation rate varies from 0% to 1.81%,the overall elongation of the castings is relatively small,and the elongation of the castings in the vacuum environment is slightly larger.The tensile strength varies from 543 MPa to 919 MPa,and the undulation is large.