Influence of heat treatment on the microstructure and tensile properties of HIPped CM247LC

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Authors

Colleges, School and Institutes

External organisations

  • DSTL

Abstract

The aim of this study is to examine the influence of heat treatment on the microstructure and high temperature tensile properties of Hot Isostatically Pressed (HIPped) CM247LC nickel-based superalloy. CM247LC powder has been HIPped at the γ' solvus temperature and heat-treated to produce different microstructures. Different solution treatment temperatures below the γ' solvus- and different times have been investigated, particularly with respect to the development of optimum high temperature (>750°C) properties. Microstructural analysis using scanning electron microscopy (SEM) and tensile testing at 750°C were performed on as-HIPped and post-HIPped heat-treated samples. In the as-HIPped condition the microstructure consisted of a bi-modal γ' distribution of coarse, irregular γ' decorating grain boundaries and fine (1μm) cuboidal γ' distributed homogeneously within grains. It has been found that dissolution of the prior γ' and the volume fraction of thermally induced porosity (TIP) increase as solution temperature approaches the γ' solvus temperature, even though the solution treatment temperature is below the HIP temperature. Subsolvus solution treatment dissolves a significant fraction of the prior γ' and yields a matrix of fine (0.3-0.5 μm) cuboidal secondary γ', whilst retaining some grain boundary primary γ' which contribute to grain boundary serrations, benefiting high temperature properties. Ageing was shown to affect the population of the fine γ' and lead to a further increase in strength. It is concluded that the optimum heat treatment requires a balance of microstructural refinement and minimal opening of pores.

Details

Original languageEnglish
Title of host publicationAdvances in Powder Metallurgy and Particulate Materials - Proceedings of the 2015 International Conference on Powder Metallurgy and Particulate Materials, PowderMet 2015
Publication statusPublished - 2015
Event2015 International Conference on Powder Metallurgy and Particulate Materials, PowderMet 2015 - San Diego, United States
Duration: 17 May 201520 May 2015

Conference

Conference2015 International Conference on Powder Metallurgy and Particulate Materials, PowderMet 2015
CountryUnited States
CitySan Diego
Period17/05/1520/05/15

Keywords

  • Gamma prime' (γ'), Heat treatment, HIPped CM247LC, Mechanical properties, Microstructure, Thermally induced porosity