Characterization and Evaluation of Aged 20Cr32Ni1Nb Stainless Steels

  • Author / Creator
    Dewar, Matthew P
  • 20Cr-32Ni-1Nb stainless steel alloys are commonly used in hydrogen reformer manifolds for transporting hot hydrogen by-products at 750-950 celcius. After long periods of exposure, embrittling secondary carbides and intermetallic phases can precipitate at the grain boundaries which can drastically reduce the ductility, and the repair weldability of the alloy. The intermetallic silicide, G-phase, is commonly observed in 20Cr-32Ni-1Nb stainless steels, and is prone to liquation cracking during welding operations. G-phase is deleterious to the material, where a high degree of G-phase coarsening will render the material unweldable.

    The present work will investigate various methods in mitigating G-phase precipitation. Variations in casting methods, wall thickness, homogenization treatments, and alloy chemistry will be examined by evaluating their microstructure after periodically aging the samples. Thermodynamic equilibrium modeling using computational thermodynamic tools will be used to optimize the 20Cr-32Ni-1Nb chemistry following ASTM specifications.

  • Subjects / Keywords
  • Graduation date
    Spring 2013
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.