MICROSTRUCTURES AND PARTITIONING RATIOS OF ALLOYING ELEMENTS IN RHENIUM CONTAINING NICKEL-BASED SINGLE-CRYSTAL SUPERALLOYS

In order to obtain some criteria for determining the optimum compositions of rhenium (Re) containing nickel-based single crystal superalloys, the phase stability and the partition ratios of alloying elements between gamma and gamma' phases were investigated using the Ni-10Cr-12Al-1.2Ti-2.6Ta-2.0W-0.7Mo-0 approximately 1Re (mol%) alloys. Most of Re atoms were found to be distributed mainly in the gamma phase and alter significantly the partition ratios of the other elements between gamma and gamma' phases. It was shown that the decrease of Cr, Ta, W, Mo contents and the increase of Al content were most desirable in the design of alloys containing more than 0.25 mol% Re. Further, in order to investigate the possibility Co addition into the Re containing alloys, its effects on the phase stability and the partition ratios of elements were examined with the Ni-10Cr-12Al-1.5Ti-2.1Ta-2.3W-0.8Mo-0.25Re (mol%) alloys in which 0 approximately 9 mol% Co was substituted for Ni. It became evident from the present experiment that the Co substitution for Ni did not induce any large changes in the phase stability and also in the partition ratios of the alloying elements in this system.