Nickel base superalloys, which are gamma prime γ‘(Ni3Al, Ti) precipitation strengthened, is largely responsible for the elevated-temperature strength of the material and the higher resistance to creep deformation. The amount of γ’ depends on the chemical composition and temperature, heat treatment, these alloy are widely used in hot sections of aero-engines, land based turbines, stator parts, nozzle guide vanes, blades and integral wheels, due to its excellent elevated temperature strength and hot corrosion resistance. The γ‘ size decreases not only by the high temperature of heat treatment solution (1120 °C), the cooling environment and cooling rate are important parameter to decrease γ’ size to 0.65 μm. This paper presents the effect of heat treatment solution in base nickel IN 738 superalloy under service conditions, on the size and morphology of the gamma phase γ’ Ni3 (Al, Ti), main phase in the nickel base superalloys. Also shown coarse carbide and precipitates gamma prime size distributed and improve interdentritic spacing in the matrix after heat treatment solution.