Evaluation of P/M 718 HIPed with δ-Subsolvus Temperature

Abstract

  Recently, as the material of turbine discs for the civil airplane, P/M superalloys such as Rene95 and RR1000 have been in practical use. This is because the advantages of P/M superalloys are more pronounced in homogeneous structure, mechanical properties and yield rate than the disadvantage in the cost of the process such as HIP 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. In this study, for getting the superfine grain and high strength, the gas-atomized powder was HIPed at a δ-subsolvus temperature. The relationship between the microstructure including PPB and mechanical properties was investigated using Inconel 718, which is used widely as a heat-resistant alloy for the aerospace and energy industries. It was found that HIP treatment at a δ-subsolvus temperature brought about the superfine grain and the high proof strength, and that the increase of the solution treatment temperature reduced the PPB influence.