Abstract
The influence of Re and Ru on segregation and microstructure evolution during heat treatment has been investigated in four Ni-based single-crystal superalloys with varied contents of Re(3%—6%,mass fractions) and Ru(0%and 3%).The additions of Re and Ru lead to the more severe segregation of alloying elements in as-cast structures.However,the effects of Ru on as-cast segregation can be neglected after the stepwise solution heat treatments.The additions of Re and Ru lead to the lowerγ'-coarsening rate,more cuboidalγ'-morphology and reducedγ'-size.Electron microprobe analysis(EPMA) indicates that A1,Ta and Ni partition to theγ'-precipitates,whereas Re and Cr strongly partition to theγ-matrix.In comparison to Re and Cr,Ru and W show the less tendency to partition to theγ-matrix.Additionally,Re increases the supersaturation of Re,Cr, Co and W in theγ-matrix,whereas Ru only slightly suppresses the partition of these TCP-forming elements to theγ-matrix.
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