Study On The Relationship Between Prior Partical Boundary Of Powder Metallurgy Superalloy And The Solid Solubility Of Transition Metal Carbides In Nickel Based Alloys

In this paper,JMat Pro thermodynamic calculation software,optical microscope(OM),field emission scanning electron microscope(FE-SEM),electron probe microanalyzer(EPMA)and transmission electron microscope(TEM)were used to study the hot isostatic pressing(HIP)state powder superalloy and heat-treated Ni-MC alloy carbide structure.The solid solubility of MC type carbides(M: Ti,Zr,Hf,V,Nb,Ta)formed by transition metals M and C at 1100°C,1180°C and 1200°C in nickel was measured.At the same time,the homogenized Ni-MC alloy was long-term aging at 850°C and 950°C.The structure changes of the Ni-MC alloy after aging were observed.The solid solubility of MC type carbides in nickel after aging was measured,and meanwhile the order of MC type carbides stability in nickel were obtained.And the relationship between the prior particle boundary(PPB)in powder metallurgy superalloy and the solid solubility of MC type carbides in nickel were analyzed.The study showed that the order of solid solubility solution of MC type carbides in nickel was: Ti C>VC>Nb C>Ta C>Zr C>Hf C.And the order of solid solubility solution of MC type carbides in nickel based alloy was: Ti C>VC>Nb C>Ta C>Zr C>Hf C.It was confirmed that Ti was a surface segregation element,and Hf and Ta were non-surface segregation elements.For surface segregation elements,the lower solid solubility of MC type carbides in nickel,the greater tendency to form PPB in powdser metallurgy superalloy,and the more serious PPB it would be.For non-surface segregation elements,the lower solid solubility of MC type carbides in nickel,the less tendency to form PPB in powder metallurgy superalloy.Among the HIP Ni-20Cr-M-C alloy(M: Ti,Zr,Hf,V,Nb,Ta),only Ni-20Cr-Ti-C has a Ti C-based PPB phenomenon.Compared with the FGH4091 alloy without Hf and the FGH4098 alloy without Ta,the HIP FGH4091 alloy with 0.55% Hf and the HIP FGH4098 alloy with 2.4% Ta have no PPB phenomenon.The carbide composition in the FGH4091 alloy with 0.55%Hf and the FGH4098 alloy with 2.4% Ta was changed,and the precipitation of MC type carbides was increased.