Microstructure and Strength of HIP Sintered Ni Base Superalloy Using PREP Powder

As the material of turbine discs for the civil airplane, PM (powder metallurgy) superalloys have been in practical use. This is because the advantages of PM superalloys are more pronounced in homogeneous structure, mechanical properties and yield rate than the disadvantage in the cost of the processing cost such as HIP (Hot Isostatic Pressing) by the advance in technology to produce alloy powders. However, PPB (Prior Particle Boundary) is known to decrease the toughness and ductility of PM alloys. For these critical applications, the consolidated alloy powder particles are smashed up to break down carbide and oxide networks, known as prior particle boundaries (PPBs), and to refine the structure into a fine grain size by isothermal forging. High quality powder can be produced by Plasma Rotating Electrode Process (PREP). In this study, for getting the fine grain and high strength and elongation, the PREP powder was HIPed at a δ-subsolvus temperature because δ precipitate prevents grain growth. The relationship between the microstructure and mechanical properties was investigated using PREP powder and lower HIP temperature.