Abstract: In this paper, the following topics are discussed:the solidification structure and phase constituents in argoin atomized powder particles and the chemical analyses on particle surfaces; the microstructures and phase constituents of the alloy after hot isostatic pressing (HIP), the nature of the previous powder particle boundary (PPB) carbides and the mechanism of their formation; the improvement of microstructure in the HIPed blank with hot extrusion and the overall enhancement of high temperature tensile, stress rupture and low cycle fatigue properties with a modified final heat treatment.