Materials (Nov 2017)

The Effect of a Two-Stage Heat-Treatment on the Microstructural and Mechanical Properties of a Maraging Steel

  • Thomas Hadfield Simm,
  • Lin Sun,
  • Deri Rhys Galvin,
  • Paul Hill,
  • Martin Rawson,
  • Soran Birosca,
  • Elliot Paul Gilbert,
  • Harshad Bhadeshia,
  • Karen Perkins

DOI
https://doi.org/10.3390/ma10121346
Journal volume & issue
Vol. 10, no. 12
p. 1346

Abstract

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Maraging steels gain many of their beneficial properties from heat treatments which induce the precipitation of intermetallic compounds. We consider here a two-stage heat-treatment, first involving austenitisation, followed by quenching to produce martensite and then an ageing treatment at a lower temperature to precipitation harden the martensite of a maraging steel. It is shown that with a suitable choice of the initial austenitisation temperature, the steel can be heat treated to produce enhanced toughness, strength and creep resistance. A combination of small angle neutron scattering, scanning electron microscopy, electron back-scattered diffraction, and atom probe tomography were used to relate the microstructural changes to mechanical properties. It is shown that such a combination of characterisation methods is necessary to quantify this complex alloy, and relate these microstructural changes to mechanical properties. It is concluded that a higher austenitisation temperature leads to a greater volume fraction of smaller Laves phase precipitates formed during ageing, which increase the strength and creep resistance but reduces toughness.

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