On the role of boron on improving ductility in a new polycrystalline superalloy

Research output: Contribution to journalArticlepeer-review

Authors

  • Paraskevas Kontis
  • Enrique Alabort
  • Daniel Barba
  • Angus J. Wilkinson
  • Roger C. Reed

Colleges, School and Institutes

External organisations

  • University of Oxford

Abstract

The role of boron in promoting ductility at high temperature in a prototype nickel-based superalloy designed for industrial gas turbines is studied. Both a boron-containing and boron-free variant are tested in tension at 750 °C, with further in-situ tests carried out using scanning electron microscopy (SEM), to clarify the mechanism of ductility improvement. The improvement in ductility is observed to be greater at the lowest investigated strain rate, where the grain boundary character plays a significant role on the mechanical properties; no ductility improvement was observed at the highest investigated strain rate. The in-situ tests were also performed at 750 °C and revealed directly the greater susceptibility of the grain boundary morphology in the boron-free case to fracture and – in the boron-containing case – the mechanism of ductility enhancement. The findings are supported further by high-resolution electron backscattered diffraction (HR-EBSD) strain mapping which confirms that the distribution of elastic strain and geometrically necessary dislocation (GND) content are influenced markedly by boron addition. The mechanism through which boron indirectly enhances the mechanical properties at elevated temperatures is discussed.

Details

Original languageEnglish
Pages (from-to)489-500
Number of pages12
JournalActa Materialia
Volume124
Early online date22 Nov 2016
Publication statusPublished - 1 Feb 2017

Keywords

  • Grain boundaries, In-situ, Nickel-based superalloys, Strain mapping