PARTITION OF Hf AMONG THE PHASES AND ITS EFFECTS ON PRECIPITATES IN PM Ni--BASED SUPERALLOY FGH97

The partition behavior of hafnium among different phases in FGH97 PM(powder metallurgy) superalloy and its effects on the precipitation behaviors of MC carbide and 7' phase were studied by means of 3DAP,SEM,TEM and physiochemical phase analysis.The results showed that element Hf mainly exists in 7' phase and MC carbide,which makes 7' composition transform to(Ni, Co)3(Al,Ti,Nb,Hf),also makes MC transform to(Nb,Ti,Hf)C.With Hf addition increasing,the proportion of Hf in 7' maintains constant,but in MC carbide increases and in 7 decreases,which means that partition ratio(R\) between 7' phase and MC carbide is decreased,while partition ratio {R2) between 7' phase and 7 matrix is increased,the average partition ratio between 7' phase and MC carbide is about 1:0.1,and the average partition ratio between 7' phase and 7 matrix is about 1 '. 0.05.Hf is helpful to the precipitations of 7' phase and MC carbide,the morphology and size of 7' phase are influenced more by Hf than these of MC carbide.