Low temperature fracture properties of DIN22NiMoCr37 steel in fine grained bainite and coarse grained tempered embrittled martensite microstructures

Maria Balart, John Knott

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

An as-received (AR) DIN 22NiMoCr37 nuclear reactor pressure vessel steel has been heat treated for 1 h at austenitising temperatures of 1373 and 1473 K to obtain different austenite grain sizes. After austenitising, the samples were water quenched, tempered for 2 It at 923 K, water quenched and then held isothermally at 793 K for. 180 11 before final air-cooling. The AR condition had a tempered bainite microstructure and a prior austenite grain size of 30 mu m, whereas the heat treated conditions were tempered martensite and had a prior austenite grain size of approximately 100 pm for the 1373 K condition and 'extraordinary' large austenite grains (>1 mm diameter) for the 1473 K condition. Their low temperature fracture properties were determined and were related to the susceptibility to segregation induced embrittlement. Despite the heat treated conditions having a larger prior austenite grain size compared to the AR condition, at a given testing temperature, the tempered martensitic 1373 K condition generally exhibited higher strength and higher fracture toughness values at 123 K. The heat treated conditions generally exhibited higher local fracture stress (sigma(f)) values in 0.2 mm blunt notch SE(B)-0.4T specimens at 123 and 77 K. (c) 2007 Elsevier Ltd. All rights reserved.
Original languageEnglish
Pages (from-to)2480-2513
Number of pages34
JournalEngineering Fracture Mechanics
Volume75
Issue number8
DOIs
Publication statusPublished - 1 May 2008

Keywords

  • intergranular fracture
  • toughness testing
  • power plants
  • transgranular fracture
  • pressurised components

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