A study of the early stages of precipitation of the gamma ' -phase in the commercial Ni-base superalloy Inconel X-750 is presented. Precipitation was induced by artificial aging heat treatments at 700 degreesC during different times ranging up to 10(4) min. Positron lifetime spectroscopy experiments, following the microstructural evolution, revealed a very complicated process of nucleation and growth of the second-phase particles, involving solute clustering and solute segregation. "Frozen frames" of the evolution process, chosen on the basis of the lifetime results, were studied by coincidence Doppler technique, which sheds information on the electronic and chemical environment around the positron trapping site.