Distribution of alloying elements of a Ni-based superalloy after long-time aging is studied employing LEAP 4000X Si. Elements like Ni, Cr and Re preferentially partition to the γ phase, while Al and W have a preference for γ" phase. A local accumulation of Ni is found on the matrix side at the γ/γ" interface, leading to a reduction of interfacial free energy. The sum solute elemental concentrations of ~25 at.% and the experimental partial RDFs of Al-R (R=Re, Ru or W) exhibiting negative correlation at first-NN distances in precipitates indicate that refractory elements substitute preferentially to the Al sublattice sites. The solid-solution strengthening effect of refractory elements and the increase in precipitates volume fraction result in an increase in microhardness, compared to the base Ni-Al-Cr alloy.