EFFECT OF TRACE ELEMENT B ON MICROSTRUCTURE OF DIRECTIONALLY SOLIDIFIED Co-BASE SUPER ALLOY DZX40M

The effect of trace element B on microstructure of directionally slidified new type Co-base superalloy is studied systematically in this paper.It is found that the addition of B makes the incipient melting temperature of the alloy decline remarkably.Compared withthe alloy having a boron contenl of 0.05%,the incipient melting temperature of the alloywith 0.7% B decreases by 197℃.The primary and secondary dendrite arm spacings in-crease and the volume fraction of interdendritic carbides with fine microstructure becomesbigger with the enhancement of boron content.When the alloy is with 0.7wt%B,M_3B_2 precipitates in the interdendrites.