Sulfide Stress Cracking Susceptibility of Low Alloy Steels for Casing Application in Sour Environments

  • Author / Creator
    Huang, Weishan
  • Sulfide stress cracking (SSC) resistance of casing steels with different alloying chemistries (i.e. Ti-B and Mn-Cr-Mo) was evaluated using constant load tensile test and slow strain rate test in NACE-TM0177 environment. SSC resistance in terms of RAH2S/RAair and time to failure was found to decrease with increase of material strength. For more susceptible steels, a mix mode of transgranular and intergranular fracture was observed. For less susceptible steels, intergranular fracture was less prevalent.
    Inclusions were found to be the dominant factor contributing to SSC susceptibility. Mn-Cr-Mo steels were more susceptible to inclusions than Ti-B steels. Cracking was found to be initiated mainly from elongated inclusions such as MnS, Al-Si-O, or large globular Ca-enriched oxide inclusions. Clustering of inclusions were main SSC initiation sites. The distribution and morphology of carbides played an important role in SSC propagation. A uniform microstructure with fine globular carbides was found to improve SSC resistance.

  • Subjects / Keywords
  • Graduation date
    Fall 2012
  • 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.