Effect Of Ce Element On Microstructure And Second Phase Precipitation Behavior Of Inconel600 Alloy

The Gibbs free energy of Cerium containing compounds Ce₂O₃,Ce₂O₂S,CeO₂and CeS at the solidification temperature of alloys is calculated by thermodynamics,indicating that these substances are earlier than those of alloy solidification.Based on the theory of lattice mismatch,the crystallographic analysis of inclusions,such as Ce₂O₃?Ce₂O₂S?CeO₂?CeAlO₃?CeS?TiC?TiN?Al₂O₃?SiO₂,which may appear in the matrix,is carried out.The calculation shows that the mismatch degree of Ce₂O₃,Ce₂O₂S,Al₂O₃,CeO₂,SiO₂ and nickel is small,the heterogeneous nucleation effect of CeAlO₃ is general;the nucleation effect of CeS,TiC and TiN is poor.Based on the empirical electron theory and the theory of electrostatic action,the characteristic parameter delta between the base and the nucleation phase is used as a criterion to analyze the utility of these solid compounds as the heterogeneous nucleated base.The calculation results indicate that Ce₂O₃ and La₂O₃ of??in the largest,so the lattice electron migration trend is the largest and the heterogenous nucleation is the best.The heterogeneous nucleation effect of TiC and TiN is poor,and Al₂O₃ and SiO₂ are intermediate core core of Ni element.The nonhomogeneous nucleation effect of cerium inclusions is better than that of ordinary inclusions.The experimental alloys with different cerium content were melted in a high temperature vacuum carbon tube furnace.The precipitation behavior of the second phase in the alloy was analyzed by means of metallographic microscope,SEM and EDS.The results show that the higher the content of cerium,the more refined the grain of the alloy is,with the increase of cerium content at the grain boundary,the carbide becomes finer from the large chain bar.But when the content of cerium reaches1.45%,the CeNi₅ phase is formed in the long narrow region between the two grain boundaries,and the melting point of the phase is higher.The alloys with different cerium content were discontinuous at 850?and 1000?.The results showed that the oxidation rate of the sample was slow with the prolongation of the oxidation time.The higher the temperature,the greater the oxidation rate of the alloy,and the decrease of the rate of oxidation with the increase of cerium content.But when the content of cerium reaches 1.45%,it accelerates the oxidation of the alloy.