INFLUENCE OF HEAT-TREATMENT ON THE MICROSTRUCTURE OF THE SINGLE-CRYSTAL NICKEL-BASE SUPERALLOY SC16

The microstructure of the recently developed single-crystal nickel-base alloy SC16 is investigated in the as-cast state and after different heat treatments using a number of complementary experimental techniques. The chemical composition of this alloy is based on that of the polycrystalline IN738LC. The effect of cooling rate after solution treatment on the gamma' particle size on ageing is investigated and the growth kinetics of the precipitates of gamma' phase during one-and two-step ageing are described quantitatively. The chemical compositions of the matrix and the precipitate phases in various heat treated conditions are determined. The precipitate volume fractions are derived for some heat treated conditions by means of three different methods. Some of the parameters are compared with those of IN738LC.