Comparison of fracture toughness properties of advanced ferritic ods-Alloys based on 0.2t c(t) specimen tests

Charles C. Eiselt, David T. Hoelzer, Yann De Carlan, Hieronymus Hein, Marta Serrano, Pascal Diano, Herbert Schendzielorz, Andreas Seubert

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Based on the good experiences gained by using small specimens made of ferritic RPV materials, the Master Curve fracture toughness approach was applied to determine the fracture mechanical properties of oxide dispersion strengthened (ODS-) materials. A ferritic ODS-Alloy (Fe-14Cr-1W-Ti-Y2O3) has been produced through the powder metallurgical production path via hot extrusion and hot isostatic pressing (HIP). Optimized oxide dispersion strengthened (ODS)-Alloys have a promising potential to meet the foreseen requirements of components in future Gen IV power plants due to their high creep strength and swelling resistance under irradiation at elevated operational temperatures. The fracture toughness was characterized with mini 0.2T C(T) specimens in different material orientations (R-L / L-R) in the ductile-brittle and upper shelf region in the un-irradiated state, accounting especially for the ODS-material's anisotropy as one key effect of manufacturing. Despite all tests were performed in orientation required by ASTM standards E 1921 and E 1820 not all validity criteria (e.g. height of yield strength, evenness of the crack, admissible K during testing or admissible stable crack growth) were met by the ODS-material: consequently, a valid T0 value and a standard-compliant Master Curve could not be determined for the ODS-material in the transition region especially in the respective R-L orientation, also due to a comparably low fracture toughness over the whole evaluated temperature range. Promising fracture toughness properties were obtained in the crack growth direction perpendicular to the prior main deformation (extrusion) direction, where a KJQ value of 196 MPa√m at T=22°C was measured. Within the ductile regime, only a JQ = J0.2BL technical initiation toughness value could be calculated and at T=22°C, a comparably large JQ of 137kJ/m2 is obtained for specimens with crack growth direction perpendicular to the extrusion direction, while in extrusion direction the toughness is again low. In addition two further ODS-materials (14YWT and PM2000) were tested and compared to the alloys above. Nonconformances of ODS relating to the material requirements in ASTM standards E1921 and E1820 were finally detected and explained.

Original languageEnglish
Title of host publicationCodes and Standards
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791850367
DOIs
StatePublished - 2016
EventASME 2016 Pressure Vessels and Piping Conference, PVP 2016 - Vancouver, Canada
Duration: Jul 17 2016Jul 21 2016

Publication series

NameAmerican Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP
Volume1B-2016
ISSN (Print)0277-027X

Conference

ConferenceASME 2016 Pressure Vessels and Piping Conference, PVP 2016
Country/TerritoryCanada
CityVancouver
Period07/17/1607/21/16

Keywords

  • Fracture toughness
  • JQ
  • KJc(1T)
  • Master Curve
  • Mini 0.2T C(T) specimens
  • ODS
  • high temperature materials

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